Solid State Relay Technical Information

Solid State Relay Technical Information
Solid State Relays
Technical Information
Glossary
Terms
Circuit functions
Input
Output
Characteristics
Others
Meaning
Photocoupler
Phototriac coupler
Transfers the input signal and insulates inputs and outputs as well.
Zero cross circuit
A circuit which starts operation with the AC load voltage at close to zero-phase.
Trigger circuit
A circuit for controlling the triac trigger signal, which turns the load current ON and OFF.
Snubber circuit
A circuit consisting of a resistor R and capacitor C, which prevents faulty ignition from occurring
in the SSR triac by suppressing a sudden rise in the voltage applied to the triac.
Input impedance
The impedance of the input circuit and the resistance of current-limiting resistors used. Impedance varies with the input signal voltage in case of the constant current input method.
Operating voltage
Minimum input voltage when the output status changes from OFF to ON.
Reset voltage
Maximum input voltage when the output status changes from ON to OFF.
Operating voltage
The permissible voltage range within which the voltage of an input signal voltage may fluctuate.
Rated voltage
The voltage that serves as the standard value of an input signal voltage.
Input current
The current value when the rated voltage is applied.
Leakage current
The effective value of the current that can flow into the output terminals when a specified load
voltage is applied to the SSR with the output turned OFF.
Load voltage
The effective supply voltage at which the SSR can be continuously energized with the output terminals connected to a load and power supply in series.
Maximum load current
The effective value of the maximum current that can continuously flow into the output terminals
under specified cooling conditions (i.e., the size, materials, thickness of the heat sink, and an ambient temperature radiating condition).
Minimum load current
The minimum load current at which the SSR can operate normally.
Output ON voltage drop
The effective value of the AC voltage that appears across the output terminals when the maximum load current flows through the SSR under specified cooling conditions (such as the size,
material, and thickness of heat sink, ambient temperature radiation conditions, etc.)
Dielectric strength
The effective AC voltage that the SSR can withstand when it is applied between the input terminals and output terminals of I/O terminals and metal housing (heat sink) for more than 1 minute.
Insulation resistance
The resistance between the input and output terminals of I/O terminals and metal housing (heat
sink) when DC voltage is imposed.
Operating time
A time lag between the moment a specified signal voltage is imposed to the input terminals and
the output is turned ON.
Release time
A time lag between the moment the imposed signal input is turned OFF and the output is turned
OFF.
Ambient temperature and
humidity (operating)
The ranges of temperature and humidity in which the SSR can operate normally under specified
cooling, input/output voltage, and current conditions.
Storage temperature
The temperature range in which the SSR can be stored without voltage imposition.
Withstand surge current
(See note.)
The maximum non-repeat current that can flow to the SSR. Expressed using the peak value at
the commercial frequency in one cycle.
Counter-electromotive force Extremely steep voltage rise which occurs when the load is turned ON or OFF.
Recommended applicable
load
The recommended load capacity which takes into account the safety factors of ambient temperate and inrush current.
Bleeder resistance
The resistance connected in parallel to the load in order to increase apparently small load currents, so that the ON/OFF of minute currents functions normally.
Note: This value was conventionally expressed as the “withstand inrush current”, but has been changed to “withstand surge current” because the
former term was easily mistaken for inrush current of loads.
Solid State Relays
Technical Information
361
Overview of SSRs
■ What Are SSRs?
Difference between SSRs and
Mechanical Relays
SSRs (Representative Example of Switching
for AC Loads)
SSRs consist of electronic parts with no mechanical contacts.
Therefore, SSRs have a variety of features that mechanical relays do
not incorporate. The greatest feature of SSRs is that SSRs do not
use switching contacts that will physically wear out.
Light
Phototriac
coupler
Triac
Phototriac coupler
No operation
noise
They provide high-speed, high-frequency switching operations.
They have no contact failures.
They generate little noise.
They have no operation noise.
Most SSRs are
SPST-NO
Long life
Input circuit
SSRs are ideal for a wide range of applications due to the following
performance characteristics.
•
•
•
•
Output
No arcing
Trigger circuit
Furthermore, SSRs employ optical semiconductors called
photocouplers to isolate input and output signals. Photocouplers
change electric signals into optical signals and relay the signals
through space, thus fully isolating the input and output sections while
relaying the signals at high speed.
Triac
Input
Zero cross function
SSRs (Solid State Relays) have no movable contacts. SSRs are not
very different in operation from mechanical relays that have movable
contacts. SSRs, however, employ semiconductor switching
elements, such as thyristors, triacs, diodes, and transistors.
Configuration of SSRs
High-speed,
high-frequency
switching
Isolated input circuit
Minimal
noise
generation
Heat
dissipation
is required.
A surge
voltage
may damage
the elements.
Snubber circuit
Drive circuit
Output circuit
Electromagnetic Relay (EMR)
Electrical isolation
Semiconductor
output element
Resistor
Power MOSFET, power
Contact
Resistor, capacitor,
and varistor
Diode, capacitor, resistor,
and transistor
Photocoupler
SSR
Component
Configuration
Phototriac coupler
Diode, LED, resistor,
and transistor
SSR Circuit
Configuration
Input
terminals
An EMR generates electromagnetic force when input voltage is
applied to the coil. The electromagnetic force moves the armature
that switches the contacts in synchronization. EMRs are not only
mounted to control panels, but also used for a wide range of applications. The principle of the operation of EMRs is simple and it is possible to manufacture EMRs at low costs.
Output
terminals
transistor, thyristor,
and triac
Input circuit
Drive circuit
Input
terminals
Output
terminals
Input
Output
Electromagnetic
force
Arc
generation
LED
Leakage
current
Photocoupler
Coil
Contact failures
may result
Capacitor
Possible bouncing
and chattering
Contact
Multi-pole
construction possible
Power transistor (for DC loads)
Power MOS FET (for AC and DC loads)
Thyristor (for AC loads)
Triac (for AC loads)
Service life of 100,000
to 100,000,000
operations
Coil
Output
Operation noise
No leakage current
Input
Rated operating voltage
± tolerance (10%)
362
Solid State Relays
Technical Information
Wide ranges of power
supply voltages and
load power supply
voltages
Control of SSRs
ON/OFF control is a form of control where a heater is turned ON or
OFF by turning an SSR ON or OFF in response to voltage output
signals from a Temperature Controller. The same kind of control is
also possible with an electromagnetic relay but if control where the
heater is turned ON and OFF at intervals of a few seconds over a
period of several years, then an SSR must be used.
With cycle control (G32A-EA), output voltage is turned ON/OFF at a
fixed interval of 0.2 s. Control is performed in response to current
output from a Temperature Controller in the range 4 to 20 mA.
The basic principle used for optimum cycle control is zero cross
control, which determines the ON/OFF status each half cycle. A
waveform that accurately matches the average output time is output.
The accuracy of the zero cross function is the same as for
conventionally zero cross control.
ON/OFF Control
Cycle Control
With conventional zero cross control, however, the output remains
ON continuously for a specific period of time, whereas with optimum
cycle control, the ON/OFF status is determined each cycle to
improve output accuracy.
Precaution for Cycle Control and Optimum Cycle Control
With cycle control, inrush current flows five times every second
(because the control cycle is 0.2 s). With a transformer load, the
following problems may occur due to the large inrush current
(approximately 10 times the rated current), and controlling the
power at the transformer primary side may not be possible.
1. The SSR may be destroyed if there is not sufficient leeway in
the SSR rating.
2. The breaker on the load circuit may be tripped.
With phase control, output is changed every half-cycle in response to
current output signals in the range 4 to 20 mA from a Temperature
Controller. Using this form of control, high-precision temperature
control is possible, and is used widely with semiconductor equipment.
Optimum Cycle Control
Phase Control
(High-accuracy Zero Cross Control)
(Single Phase)
ON/OFF status determined each half cycle.
ON OFF
ON
2s
Temperature
Controller
OFF ON
OFF
Half a cycle
2s
Voltage output
SSR
Enables low-cost, noiseless
operation without maintenance
requirements.
Temperature
Controller
Current output
SSR + Cycle
Control Unit
Enables noiseless operation
with high-speed response.
SSR +
RS-485
EJ1
G3ZA
(PLC) communications Power
Controller
Many heaters can be control
using communications.
Enables noiseless operation
with high-speed response.
Temperature
Controller
Current output
Power
controller
Enables precise temperature
control and increases the
heater’s service life.
Configuration and Operating Principle
of MOS FET Relays
MOS FET relays are SSRs that use power MOS FETs in output
elements. In order to operate the power MOS FETs, photodiode
arrays are used as light-receiving elements. When current flows into
the input terminal, the LED lights. This light generates a
photoelectromotive force in the photodiode array, and this acts as a
gate voltage that turns ON the power MOS FET. By connecting 2
power MOS FETs using a source common, control of AC loads is
possible. There are models for control of DC loads, which have just
one power MOS FET.
−
Gate
Power MOS FET
Drain
Source
Gate
Varistor
Output
LED
Photodiode array
Control circuit
Input
+
Drain
Note: There is no varistor in the G3VM style MOS FET relay that is
designed to switch low signal loads.
Solid State Relays
Technical Information
363
■ SSR Internal Circuit Configuration Examples
Yes
Photo-cou(See note 1.) pler
No
Circuit configuration
Photocoupler
Input
terminals
Input
circuit
Trigger
circuit
AC load
Isolation
Zero cross
circuit
Load
Zero cross
specifications
function
Model
Triac
Snubber Output
circuit
terminals
Phototriac
G3NE
G3J
G3F
G3H
G3TA-OA
Input
terminals
Input circuit
Phototriac
coupler
Yes
Phototriac
(See note 1.)
Phototriac
coupler
Trigger
circuit
Trigger
circuit
Zero cross
circuit
Trigger
circuit
Input circuit
No
Photodiode
coupler
Snubber Output
circuit
terminals
Trigger
circuit
Snubber Output
circuit
terminals
Input
circuit
Output
transistor
Counter
electromotive
force
protective
diode
Output
terminals
Photodiode
coupler
Input
terminals
Input
circuit
G3HD-202SN
Varistor
Output
terminals
Photodiode
coupler
Input
terminals
Input
circuit
[email protected]@B
G3NH
[email protected]@B
[email protected]@B
G3FD, G3HD-X03
G3BD
G3TA-OD
G3NA-D
Photocoupler
Input
terminals
G3FM
Output
circuit
AC/DC load
Trigger
circuit
Zero cross
circuit
Photodiode
coupler
Snubber Output
circuit
terminals
Thyristor module
Drive
circuit
Photocoupler
G3PB-3(N) (three
phases) (See note 2.)
Snubber Output
circuit
terminals
Drive
circuit
---
Snubber Output
terminals
circuit
Thyristor module
Drive
circuit
DC load
Input
circuit
Snubber Output
circuit
terminals
Thyristor module
Zero cross
circuit
Input
terminals
G3PB-2(N) (three
phases) (See note 2.)
Thyristor module
Phototriac coupler
Photocoupler
Snubber Output
circuit
terminals
G3PA-VD
G3PB (single phase)
G3NA (DC input)
G3NE
Thyristor module
Phototriac coupler
Yes
Photo(See note 1.) coupler
Triac
Thyristor module
Phototriac coupler
Input
terminals
Snubber Output
circuit
terminals
Trigger
circuit
Yes
Phototriac
(See note 1.)
Triac
Trigger
circuit
Input
circuit
Zero cross
circuit
Input
terminals
Zero cross
circuit
Photocoupler
Zero cross
circuit
Input
circuit
Zero cross
circuit
Yes
Phototriac
(See note 1.)
Trigger
circuit
Phototriac coupler
Input
terminals
G3H
G3B
G3F
G3NA (AC input)
Varistor
Output
terminals
Note: 1. The zero cross function turns ON the SSR when the AC load voltage is 0 V or close to 0 V. SSRs
with the zero cross function are effective in the following ways.
• Clicking noise when a load is turned ON is reduced.
• Effects on the power supply are reduced by suppressing inrush current with loads, such as
lamps, heaters, and motors, thereby reducing inrush current protection circuits.
Output
(load voltage)
2. For 200-V models, use a triac on the output switching elements.
Input
364
Solid State Relays
Technical Information
ON
OFF
Precautions and Notes on Correct Use
Do not touch the SSR terminal section (charged section) when the
power supply is ON. For SSRs with terminal covers, be sure to attach the cover before use. Touching the charged section may
cause electric shock.
Do not touch the SSR or the heat sink either while the power supply is ON, or immediately after the power is turned OFF. The SSR/
heat sink will be hot and will cause burns.
Do not touch the SSR LOAD terminal immediately after the power
is turned OFF. The internal snubber circuit is charged and may
cause electric shock.
• Do not apply excessive voltage or current to the SSR input or output circuits, or SSR malfunction or fire damage may result.
■ Before Using the SSR
Unexpected events may occur before the SSR is used. For this reason it is important to test the SSR in all possible environments. For
example, the features of the SSR will vary according to the product
being used.
• Do not operate if the screws on the output terminal are loose, or
heat generated by a terminal error may result in fire damage.
• Do not obstruct the air flow to the SSR or heat sink, or heat generated from an SSR error may cause the output element to short, or
cause fire damage.
• Be sure to conduct wiring with the power supply turned OFF, or
electric shock may result.
• Follow the Correct Use section when conducting wiring and soldering. If the product is used before wiring or soldering are complete,
heat generated from a power supply error may cause fire damage.
• When installing the SSR directly into a control panel so that the
panel can be used as a heat sink, use a panel material with low
thermal resistance such as aluminum or steel. If a material with
high thermal resistance such as wood is used, heat generated by
the SSR may cause fire or burning.
Pulse width ( μ s)
!WARNING
All rated performance values listed in this catalog, unless otherwise
stated, are all under the JIS C5442 standard test environment (15° to
30°C, 25% to 85% relative humidity, and 88 to 106 kPa atmosphere).
When checking these values on the actual devices, it is important to
ensure that not only the load conditions, but also the operating environmental conditions are adhered to.
0.0
1μ
F
■ Input Circuit
Input-side Connection
There is variation in the input impedance of SSR’s. Therefore, do not
connect multiple inputs in series. Otherwise, malfunction may occur.
Input Noise
SSRs need only a small amount of power to operate. This is why the
input terminals must shut out electrical noise as much as possible.
Noise applied to the input terminals may result in malfunction. The
following describes measures to be taken against pulse noise and
inductive noise.
Pulse Noise
A combination of capacitor and resistor can absorb pulse noise
effectively. The following is an example of a noise absorption circuit
with capacitor C and resistor R connected to an SSR incorporating a
photocoupler.
Pulse width
Pulse voltage (V)
Note: For low-voltage models, sufficient voltage may not be applied to
the SSR because of the relationship between C, R, and the internal impedance. When deciding on a value for R, check the
input impedance for the SSR.
Inductive Noise
Do not wire power lines alongside the input lines. Inductive noise
may cause the SSR to malfunction. If inductive noise is imposed on
the input terminals of the SSR, use the following cables according to
the type of inductive noise, and reduce the noise level to less than
the must release voltage of the SSR.
Twisted-pair wire: For electromagnetic noise
Shielded cable: For static noise
A filter consisting of a combination of capacitor and resistor will effectively reduce noise generated from high-frequency equipment.
R
C
Load
E
Pulse voltage
The value of R and C must be decided carefully. The value of R must
not be too large or the supply voltage (E) will not be able to satisfy
the required input voltage value.
Filter
High-frequency
device
The larger the value of C is, the longer the release time will be, due to
the time required for C to discharge electricity.
Note: R: 20 to 100 Ω
C: 0.01 to 1 μF
Solid State Relays
Technical Information
365
Input Conditions
Input Impedance
Input Voltage Ripples
When there is a ripple in the input voltage, set the input voltage so
that the peak voltage is lower than the maximum operating voltage
and the root voltage is above the minimum operating voltage.
Peak voltage
In SSRs which have wide input voltages (such as G3F and G3H), the
input impedance varies according to the input voltage and changes
in the input current. For semiconductor-driven SSRs, changes in voltage can cause malfunction of the semiconductor, so be sure to check
the actual device before usage. See the following examples.
Applicable Input Impedance for a Photocoupler- type SSR without
Indicators (Example) G3F, G3H (Without Indicators)
Input current (mA)
Input impedance (kΩ)
Root voltage
0V
Countermeasures for Leakage Current
When the SSR is powered by transistor output, the reset voltage may
be insufficient due to leakage current of the transistor while power is
OFF. To counteract this, connect bleeder resistance R as shown in
the diagram below and set the bleeder resistance so that the voltage
applied to both ends of the resistance is less than half of the reset
voltage of the SSR.
Input Current
Input Impedance
Input voltage (V)
Applicable Input Impedance for a Photocoupler- type SSR with Indicators
(Example) G3B, G3F, G3H (With Indicators)
R≤
E
IL−I
E: Voltage applied at both ends of the bleeder resistance = half of
the reset voltage of the SSR
IL: Leakage current of the transistor
I: Reset current of the SSR
The actual value of the reset current is not given in the datasheet
and so when calculating the value of the bleeder resistance, use
the following formula.
Reset current = Minimum value of reset voltage
for SSR
Input impedance
For SSRs with constant-current input circuits (e.g., G3NA, G3PA,
G3PB), calculation is performed at 0.1 mA.
The calculation for the G3M-202P DC24 is shown below as an example.
Reset current I =
1V
1.6 kΩ
Bleeder resistance R =
1 V × 1/2
IL - 0.625 mA
An SSR has delay times called the operating time and reset time.
Loads, such as inductive loads, also have delay times called the
operating time and reset time. These delays must all be considered
when determining the switching frequency.
Solid State Relays
Input voltage (V)
Applicable Input Impedance (Example) G3CN
Input Current
Input Impedance
= 0.625 mA
ON/OFF Frequency
366
Input Current
Input Impedance
Input current (mA)
Input impedance (kΩ)
The bleeder resistance R can be obtained in the way shown
below.
Input current (mA)
Input impedance (kΩ)
R
Bleeder resistance
Technical Information
Input voltage (V)
■ Output Circuit
AC ON/OFF SSR Output Noise Surges
If there is a large voltage surge in the AC pwer supply being used by
the SSR, the C/R snubber circuit built into the SSR between the SSR
load terminals will not be sufficient to suppress the surge, and the
SSR transient peak element voltage will be exceeded, causing overvoltage damage to the SSR.
Varistors should generally be added because measuring surges is
often difficult (except when it has been confirmed that there is no
surge immediately before use).
Only the following models have a built-in surge absorbing varistor:
G3NA, G3S, G3PA, G3NE, G3NH, G3DZ (some models), G3RZ, and
G3FM. When switching an inductive load with any other models, be
sure to take countermeasures against surge, such as adding a surge
absorbing element.
In the following example, a surge voltage absorbing element has
been added.
(Reference)
1. Selecting a Diode
Withstand voltage = VRM ≥ Power supply voltage × 2
Forward current = IF ≥ load current
2. Selecting a Zener Diode
Zener voltage =
Vz < SSR withstand voltage – (Power supply voltage + 2 V)
Zener surge power =
PRSM > Vz × Load current × Safety factor (2 to 3)
Note: When the Zener voltage is increased (Vz), the Zener diode capacity (PRSM) is also increased.
AND Circuits with DC Output SSRs
Use the G3DZ or G3RZ for the following type of circuit. Do not use
standard SSRs, otherwise the circuit may not be reset
Varistor
Load
Input
Output
Logic circuit
input
SSR
Varistor
SSR
Select an element which meets the conditions in the following table
as the surge absorbing element.
Voltage
Varistor voltage
10 to 120 VAC
240 to 270 V
200 to 240 VAC
440 to 470 V
380 to 480 VAC
820 to 1,000 V
Surge resistance
1,000 A min.
Self-holding Circuits
Self-holding circuits must use mechanical relays. SSRs cannot be
used to design self-holding circuits.
Output Connections
DC ON/OFF SSR Output Noise Surges
When an inductive load (L), such as a solenoid or electromagnetic valve,
is connected, connect a diode that prevents counter-electromotive
force. If the counter-electromotive force exceeds the withstand
voltage of the SSR output element, it could result in damage to the
SSR output element. To prevent this, insert the element parallel to
the load, as shown in the following diagram and table.
Do not connect SSR outputs in parallel. With SSRs, both sides of the
output will not turn ON at the same time, so the load current cannot
be increased by using parallel connections.
Selecting an SSR for Different Loads
The following shows examples of the inrush currents for different loads.
AC
Load
Solenoid
Incandescent lamp
Motor
Relay
Capacitor
Resistive
load
Load
Absorption Element Example
Absorption
element
Diode
Diode +
Zener diode
Varistor
CR
Effectiveness
❍
❍
Δ
×
Solid State Relays
Technical Information
Normal current
Waveform
Inrush current
As an absorption element, the diode is the most effective at suppressing the counter-electromotive force. The release time for the
solenoid or electromagnetic valve will, however, increase. Be sure to
check the circuit before use. To shorten the time, connect a Zener
diode and a regular diode in series. The release time will be shortened at the same rate that the Zener voltage (Vz) of the Zener diode
is increased.
Inrush Approx. Approx. Approx. Approx. Approx. 1
current/ 10 times 10 to 15 5 to 10 2 to 3
20 to 50
Normal
times
times
times
times
current
367
1. Heater Load (Resistive Load)
5. Half-wave Rectified Circuit
A resistive load has no inrush current. The SSR is generally used
together with a voltage-output temperature controller for heater ON/
OFF switching. When using an SSR with the zero cross function,
most generated noise is suppressed. This type of load does not,
however, include all-metal and ceramic heaters. Since the resistance
values at normal temperatures of all-metal and ceramic heaters are
low, an overcurrent will occur in the SSR, causing damage. For
switching of all-metal and ceramic heaters, select a Power Controller
(G3PX, consult your OMRON representative) with a long soft-start
time, or a constant-current switch.
AC electromagnetic counters and solenoids have built-in diodes,
which act as half-wave rectifiers. For these types of loads, a halfwave AC voltage does not reach the SSR output. For SSRs with the
zero cross function, this can cause them not to turn ON. Two methods for counteracting this problem are described below.
Heater load
These two methods, however, cannot be used to switch a half-wave
rectified break coil. We recommend using an SSR that is designed to
switch DC loads.
Refer to DC ON/OFF SSR Output Noise Surges and implement
countermeasures for counter-electromotive force. Application is not
possible for 200-VAC half-wave rectified circuits (peak voltage of 283 V)
• Connect a bleeder resistance with approximately 20% of the
SSR load current.
Temperature
Controller
(voltage output)
Bleeder resistance
2. Lamp Load
A large inrush current flows through incandescent lamps, halogen
lamps, and similar devices (approx. 10 to 15 times higher than the
rated current). Select an SSR so that the peak value of inrush current
does not exceed half the withstand surge current of the SSR. Refer
to “Repetitive” (indicated by the dashed line) shown in the following
figure. When a repetitive inrush current of greater than half the withstand surge current is applied, the output element of the SSR may be
damaged.
Load
Inrush current (A. Peak)
• Use SSRs without the zero cross function.
6. Full-wave Rectified Loads
Non-repetitive
AC electromagnetic counters and solenoids have built-in diodes,
which act as full-wave rectifiers. The load current for these types of
loads has a rectangular wave pattern, as shown in the following diagram.
Repetitive
Load
Energized time (ms)
3. Motor Load
Circuit current
wave pattern
When a motor is started, an inrush current of 5 to 10 times the rated
current flows and the inrush current flows for a longer time than for a
lamp or transformer. In addition to measuring the startup time of the
motor or the inrush current during use, ensure that the peak value of
the inrush current is less than half the withstand surge current when
selecting an SSR. The SSR may be damaged by counter-electromotive force from the motor. Be sure to install overcurrent protection for
when the SSR is turned OFF.
4. Transformer Load
Accordingly, AC SSRs use a triac (which turns OFF the element only
when the circuit current is 0 A) in the output element. If the load current waveform is rectangular, it will result in an SSR reset error.
When switching ON and OFF a load whose waves are all rectified,
use a -V model or Power MOS FET Relay.
-V-model SSRs:
G3F-203SL-V, G3H-203SL-V
Power MOS FET Relay:
G3DZ, G3RZ, G3FM
When the SSR is switched ON, an energizing current of 10 to 20
times the rated current flows through the SSR for 10 to 500 ms. If
there is no load in the secondary circuit, the energizing current will
reach the maximum value. Select an SSR so that the energizing current does not exceed half the withstand surge current of the SSR.
368
Solid State Relays
Technical Information
■ Load Power Supply
7. Small-capacity Loads
Even when there is no input signal to the SSR, there is a small leakage current (IL) from the SSR output (LOAD). If this leakage current
is larger than the load release current, the SSR may fail to reset.
Rectified Currents
If a DC load power supply is used for full-wave or half-wave rectified
AC currents, make sure that the peak load current does not exceed
the maximum usage load power supply of the SSR. Otherwise, overvoltage will cause damage to the output element of the SSR.
Connect a bleeder resistance R in parallel to increase the SSR
switching current.
R<
E
IL-I
E: Load (relays etc.) reset voltage
I: Load (relays etc.) reset current
IL: Leakage current from the SSR
Full-wave rectification
Bleeder resistance standards:
100-VAC power supply, 5 to 10 kΩ, 3 W
200-VAC power supply, 5 to 10 kΩ, 15 W
Load power supply
Load
Half-wave rectification
Peak voltage
Bleeder resistance R
SSR
operating
voltage
maximum
value
0
Peak voltage
SSR
operating
voltage
maximum
value
0
Operating Frequency for AC Load
Power Supply
The operating frequency range for an AC load power supply is 47 to
63 Hz.
Low AC Voltage Loads
8. Inverter Load
Do not use an inverter-controlled power supply as the load power
supply for the SSR. Inverter-controlled waveforms become rectangular, so the dV/dt ratio is extremely large and the SSR may fail to
reset. An inverter-controlled power supply may be used on the input
side provided the effective voltage is within the normal operating voltage range of the SSR.
If the load power supply is used under a voltage below the minimum
operating load voltage of the SSR, the loss time of the voltage
applied to the load will become longer than that of the SSR operating
voltage range. See the following load example. (The loss time is
A < B.)
Before operating the SSR, make sure that this loss time will not
cause problems.
If the load voltage falls below the trigger voltage, the SSR will not turn
ON, so be sure to set the load voltage to 75 VAC minimum. (24 VAC
for the G3PA-VD and [email protected]@B.)
Trigger voltage
Voltage increase ratio
The dV/dt ratio tends to infinity,
so the SSR will not turn OFF.
0
Trigger voltage
ΔV/ΔT = dV/dt: voltage increase ratio
A
B
9. Capacitive Load
A and B: Loss time
The supply voltage plus the charge voltage of the capacitor is applied
to both ends of the SSR when it is OFF. Therefore, use an SSR
model with an input voltage rating twice the size of the supply voltage.
Voltage waveform
Limit the charge current of the capacitor to less than half the
withstand surge current of the SSR.
t
Current waveform
t
An inductance (L) load causes a current phase
delay as shown above. Therefore, the loss is not as
great as that caused by a resistive (R) load.
This is because a high voltage is already imposed
on the SSR when the input current to the SSR
drops to zero and the SSR is turned OFF.
Phase-controlled AC Power Supplies
Phase-controlled power supply cannot be used.
Solid State Relays
Technical Information
369
■ Working with SSRs
SSR Mounting and Dismounting
Direction
Leakage Current
A leakage current flows through a snubber circuit in the SSR even
when there is no power input. Therefore, always turn OFF the power
to the input or load and check that it is safe before replacing or wiring
the SSR.
Snubber circuit
Varistor
Input circuit
Trigger circuit
Switch element
Mount or dismount the SSR from the Socket perpendicular to the
Socket surface. If it is mounted or dismounted with an inclination from
the diagonal line, terminals of the SSR may bend and the SSR may
not be properly inserted in the Socket.
Wiring for Wrapping Terminal Socket
Leakage
current
Refer to the following table and conduct wiring properly. Improper
wiring may cause the lead wires to detach.
Model
Screw Tightening Torque
Tighten the SSR terminal screws properly. If the screws are not tight,
the SSR will be damaged by heat generated when the power is ON.
Perform wiring using the tightening torque shown in the following
table.
SSR Terminal Screw Tightening Torque
SSR model
Screw size
Recommended tightening
torque
Sockets, etc.
M3.5
G3NA, G3PA-10/20A
M4
0.78 to 1.18 N·m
0.98 to 1.37 N·m
G3NA, G3PA-40A
M5
1.57 to 2.35 N·m
[email protected]@75
M6
3.92 to 4.9 N·m
[email protected]@150
M8
8.82 to 9.8 N·m
Note: Excessive tightening may damage the screws. Tighten screws
to within the above ranges.
SSR Mounting Panel Quality
If the G3NA, G3NE, or G3PB models with separate heat sinks are to
be mounted directly onto the control panel, without the use of a heat
sink, be sure to use a panel material with low thermal resistance,
such as aluminum. Be sure to apply silicon grease for heat dissipation (e.g., the YG6260 from Toshiba or the G746 from Shin-Etsu) to
the mounting surface.
Do not mount the SSR on a panel with high thermal resistance such
as a panel coated with paint. Doing so will decrease the radiation efficiency of the SSR, causing heat damage to the SSR output element.
Do not mount the SSR on a panel made of wood or any other flammable material. Otherwise the heat generated by the SSR will cause
the wood to carbonize, and may cause a fire.
Surface-mounting Socket
1. Make sure that the surface-mounting socket screws are tightened
securely when mounted. If the Unit is subjected to shock or vibration and the socket mounting screws are loose, the Socket and
the SSR, or the lead wires may detach. The surface-mounting
Sockets can be snapped on to the 35-mm DIN Track.
2. Use a holding bracket to ensure proper connection between the
SSR and Socket. Otherwise the SSR may detach from the socket
if an excessive vibration or shock is applied.
Wrapping Model Applicable Sheath Number Standard Drawtype
(bit)
wires
length to
of
terminal
out
be
effective
(mm)
force
AW Dia. removed
turns
(kg)
G
(mm)
Applicable
sleeve
[email protected] Single21-A
turn wrap22-A
ping of
sheathed 23-A
line
26
0.4
43 to 44
Approx. 6 1 × 1
3 to 8
24
0.5
36 to 37
Approx. 6
4 to 13 2-B
22
0.65 41 to 42
[email protected] Normal
wrapping
20
0.8
Approx. 4 1.0 × 1.5
5 to 15
20-A
37 to 38
1-B
4 to 15 20-B
Note: The [email protected] uses a 0.65-mm-dia. wire that can be turned six
times.
The [email protected] uses a 0.8-mm-dia. wire that can be turned four
times.
Tab Terminal Soldering Precautions
Do not solder the lead wires to the tab terminal. Otherwise the SSR
(e.g., G3NE) components will be damaged.
Cutting Terminals
Do not cut the terminal using an auto-cutter. Cutting the terminal with
devices such as an auto-cutter may damage the internal components.
Deformed Terminals
Do not attempt to repair or use a terminal that has been deformed.
Otherwise excessive force will be applied to the SSR, and it will lose
its original performance capabilities.
Hold-down Clips
Exercise care when pulling or inserting the hold-down clips so that
their form is not distorted. Do not use a clip that has already been
deformed. Otherwise excessive force will be applied to the SSR,
causing it not to perform to its full capacity, and also it will not have
enough holding power, causing the SSR to be loose, and resulting in
damage to the contacts.
PCB SSR Soldering
• SSRs must be wave soldered at 260°C within five seconds. For
models, however, that conform to separate conditions, perform soldering according to the specified requirements.
• Use a rosin-based non-corrosive flux that is compatible with the
material of the SSR.
Ultrasonic Cleaning
Do not use ultrasonic cleaning. If the SSR is cleaned using ultrasonic
cleaning after it has been mounted to the PCB, resonance due to
ultrasonic waves may result in damage to the SSR’s internal components.
370
Solid State Relays
Technical Information
■ Operation and Storage
Environment Precautions
■ Safety Considerations
Error Mode
The rated value for the ambient operating temperature of the SSR is
for when there is no heat build-up. For this reason, under conditions
where heat dissipation is not good due to poor ventilation, and where
heat may build up easily, the actual temperature of the SSR may
exceed the rated value resulting in malfunction or burning.
When using the SSR, design the system to allow heat dissipation
sufficient to stay below the Load Current vs. Ambient Temperature
characteristic curve. Note also that the ambient temperature of the
SSR may increase as a result of environmental conditions (e.g., climate or air-conditioning) and operating conditions (e.g., mounting in
an airtight panel).
Operation and Storage Locations
Do not use or store the SSR in the following locations. Doing so may
result in damage, malfunction, or deterioration of performance characteristics.
• Locations subject to direct sunlight
• Usage in locations subject to ambient temperatures outside the
range specified for individual products
• Usage in locations subject to relative humidity outside the range
specified for individual products or locations subject to condensation as the result of severe changes in temperature
• Storage in locations subject to ambient temperatures outside the
range specified for individual products
• Locations subject to corrosive or flammable gases
• Locations subject to dust (especially iron dust) or salts
• Locations subject to shock or vibration
Locations subject to exposure to water, oil, or chemicals
Extended Storage of SSR
The SSR is an optimum relay for high-frequency switching and highspeed switching, but misuse or mishandling of the SSR may damage
the elements and cause other problems. The SSR consists of semiconductor elements, and will break down if these elements are damaged by surge voltage or overcurrent. Most faults associated with the
elements are short-circuit malfunctions, whereby the load cannot be
turned OFF.
Therefore, to provide a safety feature for a control circuit using an
SSR, design a circuit in which a contactor or circuit breaker on the
load power supply side will turn OFF the load when the SSR causes
an error. Do not design a circuit that turns OFF the load power supply
only with the SSR. For example, if the SSR causes a half-wave error
in a circuit in which an AC motor is connected as a load, DC energizing may cause overcurrent to flow through the motor, thus burning
the motor. To prevent this from occurring, design a circuit in which a
circuit breaker stops overcurrent to the motor.
Location
Input area
Output area
Cause
Result
Overvoltage
Input element damage
Overvoltage
Output element damage
Overcurrent
Whole Unit
Ambient temperature ex- Output element damage
ceeding maximum
Poor heat radiation
Overcurrent Protection
A short-circuit current or an overcurrent flowing through the load of
the SSR will damage the output element of the SSR. Connect a
quick-break fuse in series with the load as a short-circuit protection
measure. (Provide an appropriate non-fuse breaker to each machine.)
Design a circuit so that the protection coordination conditions for the
quick-break fuse satisfy the relationship between the SSR surge
resistance (IS), quick-break fuse current-limiting feature (IF), and the
load inrush current (IL), shown in the following chart.
Peak current (A)
Ambient Operating Temperature
If the SSR is stored for an extended period of time, the terminals will
be exposed to the air, reducing its solderability due to such effects as
oxidation. Therefore, when installing a Relay onto a board after a
long time in storage, check the state of the solder before use. Also,
take preventive measures so that the terminals will not be exposed to
water, oil, or solvents while they are stored.
Vibration and Shock
Do not subject the SSR to excessive vibration or shock. Otherwise
the SSR will malfunction and may cause damage to the internal components.
To prevent the SSR from abnormal vibration, do not install the SSR in
locations or by means that will subject it to vibration from other
devices, such as motors.
Solvents
Time (unit: s)
Solid State Relays
Technical Information
Output terminal
Do not allow the SSR terminal cover to come in contact with oil.
Doing so will cause the cover to crack and become cloudy.
Output circuit
The operation indicator turns ON when current flows through the
input circuit. It does not indicate that the output element is ON.
Input indicator
Oil
Input circuit
Operation Indicator
Input terminal
Do not allow the SSR to come in contact with solvents such as thinners or gasoline. Doing so will dissolve the markings on the SSR.
371
■ Application Circuit Examples
ON/OFF Control of Three-phase
Inductive Motors
Connection to Sensors
Motor
Load power supply
The SSR connects directly to a Proximity Sensor or Photoelectric
Sensor.
(Brown)
Sensor
(Black)
R
Input signal
source
S
Threephase
power
supply
T
(Blue)
Sensors: TL-X Proximity Sensor
E3S Photoelectric Sensor
Forward and Reverse Operation of
Three-phase Inductive Motors
Incandescent lamp
Input
signal
source
Load power supply
Switching Control of Incandescent
Lamps
The SSR may be damaged due to phase short-circuiting if the SSR
malfunctions with noise in the input circuit of a SSR. To protect the
SSR from phase short-circuiting damage, a protective resistance R
may be inserted into the circuit.
Input signal
source and
Temperature
Controller
INPUT
Load power supply
Temperature Control of Electric
Furnaces
Load
heater
The value of the protective resistance R must be determined according to the withstanding inrush current of the SSR. For example, the
G3NA-220B withstands an inrush current of 220 A. The value of the
protective resistance R is obtained from the following.
R > 220 V x
Obtain the consumption power of the resistance from the following.
P = I2R x Safety factor
(I = Load current, R = Protective resistance, Safety factor = 3 to 5)
Motor
Load power supply
C
Note: 1. The voltage between the load terminals of either SSR 1 or
SSR 2 when turned OFF is approximately twice as high as
the supply voltage due to LC coupling. Be sure to use an
SSR model with a rated output voltage of at least twice the
supply voltage.
For example, if forward/reverse operation is to be performed
on a single-phase inductive motor with a supply voltage of
100 VAC, the SSR must have an output voltage of 200 VAC
or higher.
2. Make sure that there is a time lag of 30 ms or more to switch
over SW1 and SW2.
3. Resistor to limit advanced phase capacitor discharge current. To select a suitable resistor, consult with the manufacturer of the motor.
372
Solid State Relays
2 /200A = 1.4 Ω
Considering the circuit current and ON time, insert the protective
resistance into the side that reduces the current consumption.
Forward and Reverse Operation of
Single-phase Inductive Motors
L
Make sure that signals input into the individual SSRs are proper if the
SSRs are applied to the forward and reverse operation of a threephase motor. If SW1 and SW2 as shown in the following circuit diagram are switched over simultaneously, a phase short-circuit will
result on the load side, which may damage the output elements of
the SSRs. This is because the SSR has a triac as an output element
that is turned ON until the load current becomes zero regardless of
the absence of input signals into the SSR. Therefore, make sure that
there is a time lag of 30 ms or more to switch over SW1 and SW2.
Technical Information
Inrush Currents to Transformer Loads
Load Power Supply Voltage: 110 V
The inrush current from a transformer load will reach its peak when
the secondary side of the transformer is open, when no mutual reactance will work. It will take half a cycle of the power supply frequency
for the inrush current to reach its peak, the measurement of which
without an oscilloscope will be difficult.
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected] G3NA G3NE G3NH
resistance
(A)
current
(Ω)
resistance
(A)
5.2 min.
30
60
---
[email protected]
[email protected]
---
2.1 to 5.1
75
150
[email protected]
[email protected]
[email protected]
[email protected]
---
1.5 to 2.0
110
220
[email protected]
[email protected]
[email protected]
[email protected]
---
0.71 to 1.4 220
440
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
---
---
The withstand surge current of OMRON’s SSRs is specified on
condition that the SSRs are in non-repetitive operation (one or two
operations). If your application requires repetitive SSR switching, use
an SSR with an inrush current resistance twice as high as the rated
value (I peak).
0.39 to
0.70
400
800
---
---
---
[email protected]
0.18 to
0.38
900
1,800
---
---
---
[email protected]
In the case above, use the [email protected]@[email protected] with an withstand surge current of 207.4 A or more.
Load Power Supply Voltage: 120 V
The DC resistance of primary side of the transformer can be
calculated back from the withstand surge current by using the
following formula.
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected] G3NA G3NE G3NH
resistance
(A)
current
(Ω)
resistance
(A)
The inrush current can be, however, estimated by measuring the DC
resistance of primary side of the transformer.
Due to the self-reactance of the transformer in actual operation, the
actual inrush current will be less than the calculated value.
I peak = V peak/R = ( 2 × V) /R
If the transformer has a DC resistance of 3Ω and the load power
supply voltage is 220 V, the following inrush current will flow.
I peak = (1.414 × 220)/3 = 103.7 A
R = V peak/I peak = ( 2 × V) /I peak
5.7 min.
30
60
---
[email protected]
[email protected]
---
2.3 to 5.6
75
150
[email protected]
[email protected]
[email protected]
[email protected]
---
1.6 to 2.2
110
220
[email protected]
[email protected]
[email protected]
[email protected]
---
0.78 to 1.5 220
440
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
---
---
The underlined two digits refer to the rated current (i.e., 40 A in the
case of the above model).
0.43 to
0.77
400
800
---
---
---
[email protected]
Three digits may be used for the G3NH only.
0.19 to
0.42
900
1,800
---
---
---
[email protected]
For applicable SSRs based on the DC resistance of the primary side
of the transformer, refer to the tables below.
These tables list SSRs with corresponding inrush current conditions.
When using SSRs to actual applications, however, check that the
steady-state currents of the transformers satisfy the rated current
requirement of each SSR.
SSR Rated Current
[email protected]@[email protected]
G3NH:
[email protected] = 75 A
[email protected] = 150 A
Load Power Supply Voltage: 200 V
Condition 1: The ambient temperature of the SSR (the temperature
inside the panel) is within the rated value specified.
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected]
G3NA G3NE G3NH
resistance
(A)
current
(Ω)
resistance
(A)
Condition 2: The right heat sink is provided to the SSR.
Load Power Supply Voltage: 100 V
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected]
G3NA G3NE G3NH
resistance
(A)
current
(Ω)
resistance
(A)
4.8 min.
30
60
---
[email protected]
[email protected]
---
1.9 to 4.7
75
150
[email protected]
[email protected]
[email protected]
[email protected]
---
1.3 to 1.8
110
220
[email protected]
[email protected]
[email protected]
[email protected]
---
0.65 to 1.2 220
440
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
---
---
0.36 to
0.64
400
800
---
---
---
[email protected]
0.16 to
0.35
900
1,800
---
---
---
[email protected]
9.5 min.
30
60
---
[email protected]
[email protected]
---
3.8 to 9.4
75
150
[email protected]
[email protected]
[email protected]
[email protected]
---
2.6 to 3.7
110
220
[email protected]
[email protected]
[email protected]
[email protected]
---
1.3 to 2.5
220
440
[email protected]
[email protected]
[email protected]
[email protected]
[email protected]
---
---
0.71 to 1.2 400
800
---
---
---
[email protected]
0.32 to
0.70
1,800
---
---
---
[email protected]
Solid State Relays
900
Technical Information
373
Load Power Supply Voltage: 480 V
Load Power Supply Voltage: 220 V
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected] G3NA G3NE
resistance
(A)
current
(Ω)
resistance
(A)
10.4 min. 30
60
[email protected] [email protected]
4.2 to 10.3 75
150
[email protected] [email protected] [email protected]
[email protected]
2.9 to 4.1 110
220
[email protected] [email protected] [email protected]
[email protected]
1.5 to 2.8 220
440
[email protected] [email protected] [email protected]
[email protected]
[email protected]
0.78 to 1.4 400
800
------0.35 to
900
1,800
------0.77
G3NH
-----
9.1 min.
75
150
---
[email protected]
---
---
6.2 to 9.0
110
220
[email protected]
[email protected]
[email protected]
---
---
---
3.1 to 6.1
220
440
[email protected]
---
---
---
---
Transformer Tap Selection
[email protected]
[email protected]
Load Power Supply Voltage: 240 V
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected] G3NA G3NE
resistance
(A)
current
(Ω)
resistance
(A)
11.4 min. 30
60
[email protected] [email protected]
4.6 to 11.3 75
150
[email protected] [email protected] [email protected]
[email protected]
3.1 to 4.5 110
220
[email protected] [email protected] [email protected]
[email protected]
1.6 to 3.0 220
440
[email protected] [email protected] [email protected]
[email protected]
[email protected]
0.85 to 1.5 400
800
------0.38 to
900
1,800
------0.84
Load heater
N2
---------
■ Designing SSR Circuits
Heat Radiation Designing
1. SSR Heat Radiation
[email protected]
[email protected]
Triacs, thyristors, and power transistors are semiconductors that can
be used for an SSR output circuit. These semiconductors have a
residual voltage internally when the SSR is turned ON. This is called
output-ON voltage drop. If the SSR has a load current, the Joule
heating of the SSR will result consequently. The heating value P (W)
is obtained from the following formula.
Heating value P (W) = Output-ON voltage drop (V) × Carry current
(A)
G3NH
For example, if a load current of 8 A flows from the G3NA-210B, the
following heating value will be obtained.
-----
If the SSR employs power MOS FET for SSR output, the heating
value is calculated from the ON-state resistance of the power
MOS FET instead.
---
In that case, the heating value P (W) will be obtained from the
following formula.
P = 1.6 V × 8 A = 12.8 W
[email protected]
[email protected]
P (W) = Load current2 (A) × ON-state resistance (Ω)
If the G3RZ with a load current of 0.5 A is used, the following heating
value will be obtained.
P (W) = 0.52 A × 2.4 Ω = 0.6 W
8.3 min.
75
150
---
[email protected]
---
---
5.7 to 8.2
110
220
[email protected]
[email protected]
[email protected]
---
---
2.9 to 5.6
220
440
[email protected]
[email protected]
---
---
---
1.6 to 2.8
400
800
---
---
---
[email protected]
1,800
---
---
---
[email protected]
Solid State Relays
N1
SSR2
TransInrush
SSR
Applicable SSR
former DC current inrush
G3P≅
G3NA G3NE G3NH
resistance
(A)
current
(Ω)
resistance
(A)
374
See the following example. The power supply voltage is at 200 V, N1
is 100, N2 is 100, and SSR2 is ON. Then the difference in voltage
between output terminals of SSR1 is at 400 V (i.e., twice as high as
the power supply voltage).
SSR1
Load Power Supply Voltage: 440 V
0.70 to 1.5 900
SSRs can be used to switch between transformer taps. In this case,
however, be aware of voltage induced on the OFF-side SSR. The
induced voltage increases in proportion to the number of turns of the
winding that is almost equivalent to the tap voltage.
G3NH
Load Power Supply Voltage: 400 V
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected] G3NA G3NE
resistance
(A)
current
(Ω)
resistance
(A)
7.6 min.
75
150
[email protected] --5.2 to 7.5 110
220
[email protected] [email protected] [email protected]
2.6 to 5.1 220
440
[email protected] [email protected]
1.5 to 2.5 400
800
------0.63 to 1.4 900
1,800
-------
Transformer Inrush
SSR
Applicable SSR
DC
current inrush
[email protected] G3NA G3NE G3NH
resistance
(A)
current
(Ω)
resistance
(A)
The ON-state resistance of a power MOS FET rises with an increase
in the junction temperature of a power MOS FET. Therefore, the
ON-state resistance varies while the SSR is in operation. If the load
current is 80% of the load current or higher, as a simple method, the
ON-state resistance will be multiplied by 1.5.
P (W) = 12 A × 2.4 Ω × 1.5 = 3.6 W
The SSR in usual operation switches a current of approximately 5 A
with no heat sink used. If the SSR must switch a higher current, a
heat sink will be required. The higher the load current is, the larger
the heat sink size will be. If the switching current is 10 A or more, the
size of the SSR with a heat sink will exceed a single mechanical
relay. This is a disadvantage of SSRs for circuit downsizing purposes.
Technical Information
2. Heat Sink Selection
Temperature
SSR models with no heat sinks incorporated (i.e., the G3NA, G3NE,
and three-phase G3PB) need external heat sinks. When using any of
these SSRs, select an ideal combination of the SSR and heat sink
according to the load current.
th
Fixed wall
Hot fluid
Cool fluid
tc
The following combinations are ideal, for example.
G3NA-220B: Y92B-N100
G3NE-210T(L): Y92B-N50
G3PB-235B-3H-VD: Y92B-P200
Distance
A standard heat sink equivalent to an OMRON-made one can be
used, on condition that the thermal resistance of the heat sink is
lower than that of the OMRON-made one.
For example, the Y92B-N100 has a thermal resistance of 1.63°C/W.
If the thermal resistance of the standard heat sink is lower than this
value (i.e., 1.5°C/W, for example), the standard heat sink can be
used for the G3NA-220B.
Thermal resistance indicates a temperature rise per unit (W). The
smaller the value is, the higher the efficiency of heat radiation will be.
3. Calculating Heat Sink Area
When this formula is applicable to the heat conductivity of the control
panel under the following conditions, the heat conductivity Q will be
obtained as shown below.
Average rate of overall heat transfer of control panel: k (W/m2°C)
Internal temperature of control panel: Th (°C)
Ambient temperature: Tc (°C)
Surface area of control panel: S (m2)
Q = k × (Th - Tc) × S
The required cooling capacity is obtained from the following formula
under the following conditions.
Desired internal temperature of control panel: Th (°C)
An SSR with an external heat sink can be directly mounted to control
panels under the following conditions.
• If the heat sink is made of steel used for standard panels, do not
apply a current as high as or higher than 10 A, because the heat
conductivity of steel is less than that of aluminum. Heat conductivity (in units of W·m·°C) varies with the material as described
below.
Steel: 20 to 50
Aluminum: 150 to 220
The use of an aluminum-made heat sink is recommended if the SSR
is directly mounted to control panels. Refer to the data sheet of the
SSR for the required heat sink area.
• Apply heat-radiation silicon grease (e.g., the YG6260 from
Toshiba or the G746 from Shin-Etsu) or a heat conductive sheet
between the SSR and heat sink. There will be a space between
the SSR and heat sink attached to the SSR. Therefore, the generated heat of the SSR cannot be radiated properly without the
grease. As a result, the SSR may be overheated and damaged
or deteriorated.
The heat dissipation capacity of a heat conduction sheet is generally inferior to that of silicon grease. If a heat conduction sheet is
used, reduce the load current by approximately 10% from the Load
Current vs. Ambient Temperature Characteristics graph.
4. Control Panel Heat Radiation Designing
Control equipment using semiconductors will generate heat, regardless of whether SSRs are used or not. The failure rate of semiconductors greatly increases when the ambient temperature rises. It is
said that the failure rate of semiconductors will be doubled when the
temperature rises 10°C (Arrhenius model).
Therefore, it is absolutely necessary to suppress the interior
temperature rise of the control panel in order to ensure the long,
reliable operation of the control equipment.
Heat-radiating devices in a wide variety exists in the control panel. As
a matter of course, it is necessary to consider the total temperature
rise as well as local temperature rise of the control panel. The following description provides information on the total heat radiation
designing of the control panel.
As shown below, the heat conductivity Q will be obtained from the
following formula, provided that th and tc are the temperature of the
hot fluid and that of the cool fluid separated by the fixed wall.
Q = k (th - tc) A
Total internal heat radiation of control panel: P1 (W)
Required cooling capacity: P2 (W)
P2 = P1 - k × (Th - Tc) × S
The overall heat transfer coefficient k of a standard fixed wall in a
place with natural air ventilation will be 4 to 12 (W/m2°C). In the case
of a standard control panel with no cooling fan, it is an empirically
known fact that a coefficient of 4 to 6 (W/m2°C) is practically applicable. Based on this, the required cooling capacity of the control panel
is obtained as shown below.
Example
• Desired internal temperature of control panel: 40°C
• Ambient temperature: 30°C
• Control panel size 2.5 × 2 × 0.5 m (W × H × D)
Self-sustained control panel (with the bottom area excluded
from the calculation of the surface area)
• SSR: 20 G3PA-240B Units in continuous operation at 30 A.
• Total heat radiation of all control devices except SSRs: 500 W
Total heat radiation of control panel: P1
P1 = Output-ON voltage drop 1.6 V × Load current 30 A ×
20 SSRs + Total heat radiation of all control devices except
SSRs = 960 W + 500 W = 1460 W
Heat radiation from control panel: Q2
Q2 = Rate of overall heat transfer 5 × (40°C − 30°C) × (2.5 m ×
2 m × 2 + 0.5m × 2 m × 2 + 2.5 m × 0.5 m) = 662.5 W
Therefore, the required cooling capacity P2 will be obtained from the
following formula.
P2 = 1,460 − 663 = 797 W
Therefore, heat radiation from the surface of the control panel is
insufficient. More than a heat quantity of 797 W needs to be radiated
outside the control panel.
Usually, a ventilation fan with a required capacity will be installed. If
the fan is not sufficient, an air conditioner for the control panel will be
installed. The air conditioner is ideal for the long-time operation of the
control panel because it will effectively dehumidify the interior of the
control panel and eliminate dust gathering in the control panel.
Axial-flow fan: OMRON’s R87B, R87F, and R87T Series
Air conditioner for control panel: Apiste’s ENC Series
Where, k is an overall heat transfer coefficient (W/m2°C). This formula is called a formula of overall heat transfer.
Solid State Relays
Technical Information
375
5. Types of Cooling Device
Axial-flow Fans (for Ventilation)
Handling the SSRs
Do Not Drop
These products are used for normal types of cooling and ventilation.
OMRON’s Axial-flow Fan lineup includes the R87F and R87T Series.
The SSR is a high-precision component. Do not drop the SSR or
subject it to excessive vibration or shock regardless of whether the
SSR is mounted or not.
The maximum vibration and shock that an SSR can withstand varies
with the model. Refer to the relevant datasheet.
The SSR cannot maintain its full performance capability if the SSR is
dropped or subjected to excessive vibration or shock resulting in possible damage to its internal components.
Heat Exchangers
The impact of shock applied to the SSR that is dropped varies, and
depends on the floor material, the angle of collision with the floor,
and the dropping height. For example, if a single SSR is dropped on
a plastic tile from a height of 10 cm, the SSR may receive a shock of
1,000 m/s2 or more.
Heat exchangers dissipate the heat inside control panels along heat
pipes. Using a heat exchanger enables the inside and outside of the
control panel to be mutually isolated, allowing use in locations
subject to dust or oil mist.
Handle SSRs in in-line packages with the same care and keep them
free from excessive vibration or shock.
Note: OMRON does not produce heat exchangers.
SSR Life Expectancy
The SSR is not subject to mechanical wear. Therefore, the endurance of the SSR depends on the rate of internal component malfunction. For example, the rate for the G3M-202P is 321 Fit
(1 Fit = 10−9 = λ (malfunctions/operation)). The MTTF calculated from
this value is as follows:
MTTF = 321/λ60 = 3.12 × 106 (operations)
The effects of heat on the solder also need to be considered in estimating the total life expectancy of the SSR. The solder deteriorates
due to heat-stress from a number of causes. OMRON estimates that
the SSR begins to malfunction due to solder deterioration approximately 10 years after it is first installed.
Air Conditioners for Control Panels
Not only do these products offer the highest cooling capacity, they
also offer resistance to dust and humidity by mutually isolating the
inside and outside of the control panel.
Note: OMRON does not produce air conditioners for control panels.
376
Solid State Relays
Technical Information
■ Mounting and Installation
Panel Mounting
If SSRs are mounted inside an enclosed panel, the radiated heat of
the SSR will stay inside, thus not only dropping the carry-current
capacity of the SSRs but also adversely affecting other electronic
device mounted inside. Open some ventilation holes on the upper
and lower sides of the control panel before use.I
The following illustrations provide a recommended mounting
example of G3PA Units. They provide only a rough guide and so be
sure to confirm operating conditions using the procedure detailed in
(4) Confirmation after Installation
1. SSR Mounting Pitch
2. Relationship between SSRs and Ducts
Panel Mounting
Duct Depth
Duct
50 mm max.
(The recommended
width is half as large
as the depth of G3PA
or less)
Between duct
and G3PA
Duct
60 mm min.
Duct
Mounting surface
Mounting direction
Vertical direction
Host and
slave
30 mm min.
80 mm min.
Better
G3PA
100 mm
Vertical
direction
Mounting surface
G3PA
G3PA
Between duct
and G3PA
10 mm
High-density or
gang mounting
Duct
The high-density or gang mounting of
a maximum of three Units is possible.
Do not mount more than three Units
closely together without providing a
10-mm space to the next group of
Units.
Do not enclose the SSR
with the duct in the depth
direction, otherwise the
heat radiation of the SSR
will be adversely affected.
Duct
Use a short duct in the
depth direction.
Better
Mounting surface
Duct
3.Ventilation
Be aware of air flow
Duct
G3PA
Air flow
Metal
base
Duct
Duct
Ventilation
outlet
Duct
G3PA
G3PA
G3PA
If the height of the ducts cannot
be lowered, place the SSRs on a
metal base so that they are not
surrounded by the ducts.
Duct
Duct
Air inlet
Duct
If the air inlet or air outlet has a filter, clean the filter regularly to prevent it from
clogging and ensure an efficient flow of air.
Do not locate any objects around the air inlet or air outlet, or otherwise the objects
may obstruct the proper ventilation of the control panel.
A heat exchanger, if used, should be located in front of the G3PA Units to ensure the
efficiency of the heat exchanger.
Solid State Relays
Technical Information
377
4. Confirmation after Installation
The above conditions are typical examples confirmed by
OMRON. The application environment may affect conditions and
ultimately the ambient temperature must be measured under power
application to confirm that the load current-ambient temperature
ratings are satisfied for each model.
Ambient Temperature Measurement Conditions
1. Measure the ambient temperature under the power application
conditions that will produce the highest temperature in the
control panel and after the ambient temperature has become
saturated.
2. Refer to Figure 1 for the measurement position. If there is a
duct or other equipment within the measurement distance of
100 mm, refer to Figure 2. If the side temperature cannot be
measured, refer to Figure 3.
100 mm
Ambient
temperature
measurement
position
Figure 1: Basic Measurement Position
for Ambient Temperature
L/2
Other
Device
Ambient
temperature
measurement
position
L (100 mm or less)
Figure 2: Measurement Position when a
Duct or Other Device is Present
Ambient
temperature
measurement
range
100 mm
Figure 3: Measurement Position when Side
Temperature Cannot be Measured
3. If more than one row of SSRs are mounted in the control
panel, measure the ambient temperature of each row, and use
the position with the highest temperature.
Consult your OMRON dealer, however, if the measurement
conditions are different from those given above.
Definition of Ambient Temperature
SSRs basically dissipate heat by natural convection. Therefore,
the ambient temperature is the temperature of the air that
dissipates the heat of the SSR.
378
Solid State Relays
Technical Information
PCB-mounting SSRs
Suitable PCBs
PCB Material
PCBs are classified into epoxy PCBs and phenol PCBs. The following table lists the characteristics of these PCBs. Select one, taking into account
the application and cost. Epoxy PCBs are recommended for SSR mounting in order to prevent the solder from cracking.
Item
Electrical
characteristics
Mechanical
characteristics
Economical
efficiency
Application
Epoxy
Glass epoxy
Paper epoxy
High insulation resistance.
Inferior to glass epoxy but superior to
paper phenol PCBs.
Highly resistive to moisture absorption.
The dimensions are not easily af- Inferior to glass epoxy but superior to
fected by temperature or humidity. paper phenol PCBs.
Ideal for through-hole or multi-layer PCBs.
Expensive
Rather expensive
Phenol
Paper phenol
New PCBs are highly insulation-resistive but easily
affected by moisture absorption and cannot maintain
good insulation performance over a long time.
The dimensions are easily affected by temperature
or humidity.
Not suitable for through-hole PCBs.
Inexpensive
Applications in comparatively good environments
Applications that require high reli- Applications that may require less
ability.
reliability than those for glass epoxy with low-density wiring.
PCBs but require more reliability
than those of paper phenol PCBs.
PCB Thickness
Mounting Space
The PCB may warp due to the size, mounting method, or ambient
operating temperature of the PCB or the weight of components
mounted to the PCB. Should warping occur, the internal mechanism
of the SSR on the PCB will be deformed and the SSR may not provide its full capability. Determine the thickness of the PCB by taking
the material of the PCB into consideration.
The ambient temperature around the sections where the SSR is
mounted must be within the permissible ambient operating temperature. If two or more SSRs are mounted closely together, the SSRs
may radiate excessive heat. Therefore, make sure that the SSRs are
separated from one another at the specified distance provided in the
datasheet. If there is no such specification, maintain a space that is
as wide as a single SSR.
Terminal Hole and Land Diameters
Refer to the following table to select the terminal hole and land diameters based on the SSR mounting dimensions. The land diameter
may be smaller if the land is processed with through-hole plating.
Hole dia. (mm)
Nominal value
Tolerance
0.6
±0.1
0.8
1.0
1.2
1.3
1.5
1.6
2.0
Provide adequate ventilation to the SSRs as shown in the following
diagram.
Minimum land dia.
(mm)
1.5
1.8
2.0
2.5
2.5
3.0
3.0
3.0
Solid State Relays
Technical Information
379
Mounting SSR to PCB
Read the precautions for each model and fully familiarize yourself
with the following information when mounting the SSR to the PCB.
1. Do not bend the terminals to make the
Step 1
SSR self-standing, otherwise the full
SSR mounting
performance of the SSR may not be
possible.
2. Process the PCB properly according to
the mounting dimensions.
Step 2
Flux coating
Flux
Step 3
Preheating
1. The flux must be a non-corrosive rosin
flux, which is suitable to the material of
the SSR.
Apply alcohol solvent to dissolve the flux.
2. Make sure that all parts of the SSR other
than the terminals are free of the flux. The
insulation resistance of the SSR may be
degraded if there is flux on the bottom of
the SSR.
Step 5
Cooling
1. After soldering the SSR, be sure to cool down
the SSR so that the soldering heat will not
deteriorate the SSR or any other components.
2. Do not dip the SSR into cold liquid, such as a
detergent, immediately after soldering the
SSR.
Step 6
Cleaning
1. Refer to the following table for the selection of
the cleaning method and detergent.
Detergent
Boiling or dip cleaning is possible for the
SSR. Do not perform ultrasonic cleaning or
cut the terminals, otherwise the internal
parts of the SSR may be damaged. Make
sure that the temperature of the detergent is
within the permissible ambient operating
temperature of the SSR.
1. Be sure to preheat the SSR to allow better
soldering.
2. Preheat the SSR under the following
conditions.
Temperature
100°C max.
Time
1 min max.
2. Applicability of Detergents
Detergent
Chlorine Perochine
detergent Chlorosolder
Trichloroethylene
Indusco
Aqueous Holys
detergent Pure water
(pure hot water)
3. Do not use the SSR if it is left at high
temperature over a long time. This may
change the characteristics of the SSR.
Step 4
Soldering
Automatic Soldering
1. Flow soldering is recommended for
maintaining a uniform soldering quality.
Solder: JIS Z3282 or H63A
Soldering temperature: Approx. 260°C
Soldering time: Approx. 5 s
(Approx. 2 s for first time and approx. 3 s for
second time for DWS)
Perform solder level adjustments so that
the solder will not overflow on the PCB.
Manual Soldering
1. After smoothing the tip of the soldering
iron, solder the SSR under the following
conditions.
Solder: JIS Z3282, 1160A, or H63A
with rosin-flux-cored solder
Soldering iron: 30 to 60 W
Soldering temperature:
280°C to 300°C
Solder
Soldering time: Approx. 3 s
Flux
2. As shown in the above illustration,
solder with a groove for preventing flux
dispersion.
380
Solid State Relays
Applicability
OK
OK
Alcohol
IPA
Ethanol
OK
Others
Paint thinner
Gasoline
NG
Note: 1. Contact your OMRON representatives
before using any other detergent. Do
not apply Freon TMC, paint thinner, or
gasoline to any SSR.
2. The space between the SSR and PCB
may be not be adequately cleaned with
a hydrocarbon or alcohol detergent.
Actions are being taken worldwide to stop
the use of CFC-113 (chlorofluorocarbon)
and 1.1.1 trichloroethane. Your understanding and cooperation are highly appreciated.
Step 7
Coating
Technical Information
1. Do not fix the whole SSR with resin, otherwise
the characteristics of the SSR may change.
2. The temperature of the coating material must
be within the permissible ambient operating
temperature range.
Coating
Type
Applicability
Epoxy
OK
Urethane
OK
Silicone
OK
Q&A for SSRs
Q1
We think an SSR is faulty. Can a voltage tester be
used to check an SSR to see if current is flowing?
Q3
What is the difference in switching with a thyristor
and a triac?
A1
No, that is not possible.
The voltage and current in the tester’s internal circuits
are too low to check the operation of the
semiconductor element in the SSR (a triac or
thyristor). The SSR can be tested as described below
if a load is connected.
A3
There is no difference between them as long as
resistive loads are switched. For inductive loads,
however, thyristors are superior to triacs due to the
inverse parallel connection of the thyristors. For the
switching element, an SSR uses either a triac or a pair
of thyristors connected in an inverse parallel
connection.
● Testing Method
Connect a load and power supply, and check the
voltage of the load terminals with the input ON and
OFF. The output voltage will be close to the load
power supply voltage with the SSR turned OFF. The
voltage will drop to approximately 1 V with the SSR
turned ON. This is more clearly checked if the dummy
load is a lamp with an output of about 100 W.
There is a difference between thyristors and triacs in
response time to rapid voltage rises or drops. This
difference is expressed by dv/dt (V/μs). This value of
thyristors is larger than that of triacs. Triacs can switch
inductive motor loads that are as high as 3.7 kW.
Furthermore, a single triac can be the functional
equivalent of a pair of thyristors connected in an
inverse parallel connection and can thus be used to
contribute to downsizing SSRs.
100 W lamp
Load
INPUT
SSR
LOAD
Q2
What kind of applications can power MOS FET
relays be used for?
A2
1. Applications where it is not known whether the load
connected to the relay is AC or DC.
Example: Alarm output of robot controller.
2. Applications with high-frequency switching of
loads, such as for solenoid valves with internally,
fully rectified waves, where the relay (e.g., G2R)
has to be replaced frequently.
Power MOS FET relays have a longer lifetime than
other relays and so the replacement frequency is
less.
The terminals of the G3RZ are compatible with
those of the G2R-1A-S and so these models can
be exchanged.
Thyristors connected in an
inverse parallel connection
Triac
Note: dv/dt = Voltage rise rate.
V
Note:Confirm the input voltage, polarity, and output
capacity before application.
3. Applications with high-voltage DC loads.
In order to switch a 100-VDC, 1-A load with a relay,
an MM2XP or equivalent is required. With the
G3RZ power MOS FET relay, however, switching at
this size is possible.
4. Applications where SSRs are used with a bleeder
resistance.
The leakage current for power MOS FET relays is
very small (10 μA max.) and so a bleeder
resistance is not required.
ΔV
T
ΔT
ΔV/ΔT = dv/dt: Voltage rise rate
Triac
Two
thyristors
Q4
A4
Resistive load
40 A max.
Over 40 A
OK
OK
OK
OK
Inductive load
3.7 kW max. Over 3.7 kW
OK
Not as good
OK
OK
Is it possible to connect SSRs in series?
Yes, it is. SSRs are connected in series mainly to
prevent short circuit failures. Each SSR connected in
series shares the burden of the surge voltage. The
overvoltage is divided among the SSRs, reducing the
load on each.
A high operating voltage, however, cannot be applied
to the SSRs connected in series. The reason is that
the SSRs cannot share the burden of the load voltage
due to the difference between the SSRs in operating
time and reset time when the load is switched.
Input
INPUT
Output
SSR
LOAD
Load
INPUT
Solid State Relays
SSR
LOAD
Technical Information
381
Q5
What needs to be done for surge absorption
elements for SSRs for DC loads?
Q6
What is the zero cross function?
A5
Output Noise Surge Countermeasures for SSRs for
DC Load Switching
When an L load, such as a solenoid or
electromagnetic valve, is connected, connect a diode
that prevents counter-electromotive force. If the
counter-electromotive force exceeds the withstand
voltage of the SSR output element, it could result in
damage to the SSR output element. To prevent this,
insert the element parallel to the load, as shown in the
following diagram and table.
A6
The zero cross function turns ON the SSR when the
AC load voltage is close to 0 V, thus suppressing the
noise generation of the load current when the load
current rises quickly.
The generated noise will be partly imposed on the
power line and the rest will be released in the air. The
zero cross function effectively suppresses both noise
paths.
A high inrush current will flow when the lamp is turned
ON, for example. When the zero cross function is
used, the load current always starts from a point close
to 0 V. This will suppress the inrush current more than
SSRs without the zero cross function.
Load
INPUT
SSR
Without the zero cross function:
Voltage drops due to sudden change in
current and noise is generated.
As an absorption element, the diode is the most
effective at suppressing the counter-electromotive
force. The release time for the solenoid or
electromagnetic valve will, however, increase. Be sure
to check the circuit before use. To shorten the time,
connect a Zener diode and a regular diode in series.
The release time will be shortened at the same rate
that the Zener voltage (Vz) of the Zener diode is
increased.
Power
supply
voltage
Load
current
SSR
input
Table 1. Absorption Element Example
Diode
Diode +
Varistor
Zener diode
CR
Effectiveness
Most
effective
Most
effective
Ineffective
+
Somewhat
effective
+
ON
With the zero cross function:
Absorption element
+
Radiated noise
Power
supply
voltage
Load
current
+
ON
SSR
input
−
−
−
−
Reference
1. Selecting a Diode
Withstand voltage = VRM ≥ Power supply voltage × 2
Forward current = IF ≥ load current
2. Selecting a Zener Diode
Zener voltage =
Vz < (Voltage between SSR’s collector and emitter)* − (Power
supply voltage + 2 V)
Zener surge power =
PRSM > VZ × Load current × Safety factor (2 to 3)
Q7
Is it possible to connect two 200-VAC SSRs in
series to a 400-VAC load?
A7
No, it is not. The two SSRs are slightly different to
each other in operating time. Therefore, 400 VAC will
be imposed on the SSR with a longer operating time.
Note: When the Zener voltage is increased (VZ), the Zener diode
capacity (PRSM) is also increased.
382
Solid State Relays
Technical Information
Q8
A8
Is it possible to connect SSRs in parallel?
Q10
What precautions are necessary for forward/
reverse operation of the singlephase motor?
Yes, it is. SSRs are connected in parallel mainly to
prevent open circuit failures. Usually, only one of the
SSR is turned ON due to the difference in output ON
voltage drop between the SSRs.
Therefore, it is not possible to increase the load
current by connecting the SSRs in parallel.
If an ON-state SSR in operation is open, the other
SSR will turn ON when the voltage is applied, thus
maintaining the switching operation of the load.
Do not connect two or more SSRs in parallel to drive a
load exceeding the capacity each SSRs; the SSRs
may fail to operate.
A10
Refer the following table for the protection of capacitor
motors driven by SSRs.
Single-phase
Load current of
Protection of motor in
100 V
recommended SSR forward/reverse operation
R
25 W
AC 2 to 3 A
R = 6 Ω, 10 W
AC 5 A
R = 4 Ω, 20 W
40 W
60 W
R = 3 Ω, 40 to 50 W
90 W
Single-phase
Load current of
Protection of motor in
200 V
recommended SSR forward/reverse operation
R
25 W
R = 12 Ω, 10 W
AC 2 to 3 A
40 W
2.2 kW
2.2 kW G3J
M 3.7 kW
Q9
A9
60 W
Example:
It is not possible to
countrol a 3.7-kW heater
with two SSRs for 2.2kW
connected in parallel.
R = 12 Ω, 20 W
AC 5 A
R = 8 Ω, 40 W
90 W
What is silicon grease?
Special silicon grease is used to aid heat dissipation.
The heat conduction of this special compound is five
to ten times higher than standard silicon grease.
This special silicon grease is used to fill the space
between a heat-radiating part, such as an SSR, and
the heat sink to improve the heat conduction of the
SSR.
Unless special silicon grease is applied, the generated
heat of the SSR will not be radiated properly. As a
result, the SSR may break or deteriorate due to
overheating.
Precautions for Forward/Reverse Operation
1.In the following circuit, if SSR1 and SSR2 are turned
ON simultaneously, the discharge current, i, of the
capacitor may damage the SSRs. Therefore, a
minimum 30-ms time lag is required to switch between
SSR1 and SSR2. If the malfunction of the SSRs is
possible due to external noise or the counterelectromotive force of the motor, connect L or r in
series with either SSR1 or SSR2 whichever is less
frequently use. A CR absorber (consisting of 0.1-μF
capacitor withstanding 630 V and 22-Ω resistor
withstanding 2 W) can be connected in parallel to
each SSR so that the malfunctioning of the SSRs will
be suppressed.
SW1
INPUT
SW2
Motor
+
-
SSR
1
+
Available Silicon Grease Products for Heat
Dissipation
INPUT
-
Toshiba Silicone: YG6260
Shin-Etsu Silicones: G746
SSR
2
Load power supply
G3J
2.When the motor is in forward/reverse operation, a
voltage that is twice as high as the power supply
voltage may be imposed on an SSR that is OFF due to
the LC resonance of the motor.
When selecting an SSR, be careful that this voltage
does not exceed the rated load voltage of the SSR. (It
is necessary to determine whether use is possible by
measuring the actual voltage applied to the SSR on
the OFF side.)
Solid State Relays
Technical Information
383
Does an SSR have a mounting direction?
Q12
What precautions are required for high-density
mounting or gang mounting?
A11
An SSR consists of semiconductor elements.
Therefore, unlike mechanical relays that incorporate
movable parts, gravity changes have no influence on
the characteristics of the SSR.
Changes in the heat radiation of an SSR may,
however, limit the carry current of the SSR.
An SSR should be mounted vertically. If the SSR has
to be mounted horizontally, check with the SSR’s
datasheet. If there is no data available for the SSR,
use with a load current at least 30% lower than the
rated load current.
A12
In the case of high-density or gang mounting of SSRs,
check the relevant data in the SSR datasheet. If there
is no data, check that the load current applied is 70%
of the rated load current. A 100% load current can be
applied if groups of three SSRs are mounted in a
single row with a space as wide as a single SSR
between adjacent groups.
If the SSRs are mounted in two or more rows, it is
necessary to confirm the temperature rise of the SSR
separately.
With side-by-side high-density or gang mounting of
SSRs with heat sinks, reduce the load current to 80%
of the rated load current.
Refer to the SSR’s datasheet for details.
G3PA
Vertical direction
Vertical direction
Q11
DIN track
G3PE
Characteristic Data
High-density or Gang Mounting (3 or 8 Units)
Vertical mounting
Mount the SSR vertically.
Panel
G3PE-215B
Load current (A)
Vertical direction
G3PA-210B-VD
G3PA-220B-VD
G3PA-240B-VD
Do not mount more than
a group of three Units
closely together without
providing a 10-mm
space to the next group.
20
3
15
13
12
10
8
Flat Mounting
Panel
7
5.7
5
The SSR may be mounted on a flat
surface, provided that the load current
applied is 30% lower than the rated
load current.
0
-40
-20
0
20
40
60
80
100
Ambient temperature
Load current (A)
G3PE-225B
30
25
3
20
19
8
15
10
8
7
5
0
-40
-20
0
20
40
60
80
100
Ambient temperature
Example of high-density or gang mounting
DIN track
384
Solid State Relays
Technical Information
Q13
What is the non-repetitive inrush current?
Q15
Why can MOS FET relays be used for both AC and
DC loads?
A13
The datasheet of an SSR gives the non-repetitive
inrush current of the SSR. The concept of the nonrepetitive inrush current of an SSR is the same as an
absolute maximum rating of an element. Once the
inrush current exceeds the level of the non-repetitive
inrush current, the SSR will be destroyed. Therefore,
check that the maximum inrush current of the SSR in
usual ON/OFF operation is 1/2 of the non-repetitive
inrush current. Unlike mechanical relays that may
result in contact abrasion, the SSR will provide good
performance as long as the actual inrush current is a
maximum of 1/2 of the non-repetitive inrush current. If
the SSR is in continuous ON/OFF operation and a
current exceeding the rated value flows frequently,
however, the SSR may overheat and a malfunction
may result. Check that the SSR is operated with no
overheating. Roughly speaking, inrush currents that
are less than the non-repetitive inrush current and
greater than the repetitive inrush current can be
withstood once or twice a day (e.g., this level of inrush
current can be withstood in cases where power is
supplied to devices once a day).
A15
With power MOS FET relays, because 2 MOS FET
relays are connected in series in the way shown on
the right, the load power supply can be connected in
either direction. Also, because power MOS FET
elements have a high dielectric strength, they can be
used for AC loads, where the polarity changes every
cycle.
L
L
Direction of current
Q16
What are the differences between SSRs and power
MOS FET relays?
A16
Number 1: There are SSRs for DC loads and SSRs
for AC loads.
SSR for DC Loads (e.g., G3HD)
Drive circuit
Photocoupler
Input circuit
200
Region not allowing
even one occurrence
150
Non-repetitive
Output
transistor
100
Once or
twice a day
Input circuit
50
Region allowing any
number of repetitions
in one day
0
10
30 50
100 200
500 1,000
Trigger circuit
Photocoupler
Repetitive
L
SSR for AC Loads (e.g., G3H)
Zero cross
circuit
Inrush current (A. peak)
G3NE-220T
Triac
L
5,000
Carry current (ms)
Power MOS FET relays can be used for both DC loads and AC loads.
Q14
What kind of failure do SSRs have most
frequently?
Number 2: The leakage current for power MOS
FET relays is small compared to that for SSRs.
A14
OMRON's data indicates that most failures are caused
by overvoltage or overcurrent as a result of the shortcircuiting of SSRs. This data is based on SSR output
conditions, which include those resulting from the
open or short circuit failures on the input side.
The lamp (see below) is faintly light by the leakage
current. A bleeder resistance is added to prevent this.
With SSRs, a snubber circuit is required to protect the
output element.
Failure
Input
Output
SSRs
SSR
Load condition
Short
Does not turn ON.
Open
Does not turn ON.
Output triac short circuit
(80% of failures)
Does not turn OFF.
Output triac open circuit
(20% of failures)
Does not turn ON.
Bleeder resistance
Snubber circuit
Power MOS FET Relays
The leakage current is very small (10 μA max.) and so
the lamp does not light. This is because a snubber
circuit is not required to protect the MOS FET output
element. A varistor is used to protect the MOS FET.
Power MOS FET relay
A bleeder resistance is not
required and so circuits
can be simplified and
production costs reduced.
Solid State Relays
Technical Information
385
SSR Troubleshooting
No
The SSR may be
adversely affected by
the residual voltage
at the previous stage,
a leakage current, or
inductive noise
through the input
line.
Is the input
indicator OFF?
Yes
Yes
Is the operation
indicator lit?
Select Yes if
there is no
operation
indicator.
The SSR
cannot be
used unless a
sine wave
current is
supplied.
Rectangular
waveform
Yes
Is the load
current turned
OFF when the
input line is
disconnected.
Is the load
power supply
AC, DC, or a
rectangular
waveform
current?
No
AC
START
DC
Problem
The SSR stays
ON
(Short circuit)
The SSR does
not turn ON
(Open circuit
error)
Refer to
Forward and
Reverse
Operation of
Three-phase
Motor
Is the operation
indicator OFF?
Select Yes if
there is no
operation
indicator.
Use an SSR for
DC load driving.
Yes
Use a multimeter
and check the
voltage of the input
terminals with the
input connected. Is
the operating
voltage applied to
the terminals?
No
Yes
Yes
No
Is the SSR for
AC output?
Use a multimeter
and check the
voltage of the
output terminals.
Is the load voltage
applied to the
terminals?
No
Yes
No
Is the polarity
of the input
correct?
Check the
wiring.
Yes
Reconnect the
input line. The
SSR is not
broken unless it
is an SSR for
PCBs.
386
Solid State Relays
Technical Information
Is a half-wave
rectification or
phase control
power supply used
for the load while
the SSR has a
zero cross
function?
Yes
Use an SSR
that does not
have a zero
cross function.
No
The SSR has a
failure, such as
a load short
circuit or
external surge
failure.
Refer to Fullwave Rectified
Loads.
Yes
No
Yes
Is a full-wave
rectification L
load
connected?
Is the polarity
of the output
correct?
No
Is the load a
minute one
with a
maximum input
of 50 mA?
No
Is an L load,
such as a
valve,
solenoid, or
relay
connected?
No
Yes
Is the load a one
with a high inrush
current, such as a
motor, lamp, or
power
transformer?
No
Is a diode for
absorbing
counterelectromotive
force
connected?
Yes
No
Does the inrush
current of the
SSR exceed the
withstand surge
current?
Reconnect the
output line.
The SSR is not
broken.
Yes
Does the inrush
current exceed
the withstand
surge current of
the SSR?
Yes
No
No
Connect a diode for
absorbing counterelectromotive force.
Refer to DC ON/OFF
SSR Output Noise
Surges.
Yes
Yes
Is AC input
applied to the
SSR for DC
input?
Yes
Use an SSR for
AC input.
Yes
It is probable that the
SSR has an output
element failure
caused by the inrush
current. Consider
using an SSR with a
higher capacity.
No
The SSR has a
failure, such as
a load short
circuit or
external surge
failure.
Solid State Relays
Technical Information
387
All sales are subject to Omron Electronic Components LLC standard terms and conditions of sale, which
can be found at http://www.components.omron.com/components/web/webfiles.nsf/sales_terms.html
ALL DIMENSIONS SHOWN ARE IN MILLIMETERS.
To convert millimeters into inches, multiply by 0.03937. To convert grams into ounces, multiply by 0.03527.
OMRON ON-LINE
OMRON ELECTRONIC
COMPONENTS LLC
Global - http://www.omron.com
USA - http://www.components.omron.com
55 E. Commerce Drive, Suite B
Schaumburg, IL 60173
847-882-2288
Cat. No. X301-E-1b
Solid State Relays
09/11
Specifications subject to change without notice
Technical Information
Printed in USA
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