mhi history of inverter technology
1
History of inverter technology
1. What is Inverter technology?
2. Basic structure of inverter device
3. History of Inverter technology
0. Transition of inverter technology
1. What is the difference between AC inverter and DC inverter
2. Why the inverter technology evolved from AC to DC?
3. DC inverter with PAM converter (DC PAM inverter)
4. Vector control DC inverter
5. Which technology is applied to our products?
2
History of inverter technology
1. What is Inverter technology?
Inverter is a device which supplies variable frequency of power
supply on equipments
Thanks to this function, motor revolution speed can be controlled and
it leads to reduce energy consumption.
converter
AC 230V 50Hz
Comp
Motor
inverter
DC 310V
Variable
frequency
DC
3
History of inverter technology
2. Basic structure of inverter device
Inverter device consists of mainly two parts; converter and inverter
Originally the meaning of “Inverter” is changing DC power source into AC
power source.
In order to make supplied frequency variable, once the AC power source is
changed into DC at Converter part.
Converter part
AC
Diode
bridge
Smoothing
capacitor
Inverter part
DC
M
Power
transistor
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History of inverter technology
2. Basic structure of inverter device
2-1 Function of Converter
Converter part converts AC power supply into DC thanks to Diode bridge
circuit
Diode: electrical component which allows current go through on one way.
Diode Bridge circuit
-+
Input: AC
+-
+
Smoothing
capacitor
Output: DC
-
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History of inverter technology
2. Basic structure of inverter device
2-1 Function of Inverter
By signal being input on each transistor, current will go through the
motor. This signal input format is different according to the motor
(AC inverter / DC inverter)
Inverter part
(power transistor)
(IPM: Intelligent Power Module)
+
Input: DC
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History of inverter technology
3. History of Inverter technology
0. Transition of inverter technology
1. What is the difference between AC inverter and DC inverter?
<feature of AC motor / DC motor>
> Structure
> Principle
> Advantage and disadvantage
2. Why the inverter technology evolved from AC to DC?
3. DC inverter with PAM converter (DC PAM inverter)
> What is PAM?
> What is the necessity of PAM?
4. Vector control DC inverter
5. Which technology is applied to our products?
7
History of inverter technology
3-0 Transition of inverter technology
Inverter technology evolved along the technological
innovation as shown below.
Comp motor
Modulation
Voltage Waveform
AC inverter
AC motor
PWM
180degree
DC inverter
DC motor
PWM
120degree
DC inverter with
PAM converter
DC motor
PWM + PAM
120degree
DC inverter with
vector control
DC motor
PWM (+ PAM)
180degree
time
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History of inverter technology
3-1 What is the difference between AC and DC inverter
There are two main types of inverter system:
One is AC inverter, and
the other is DC inverter
Basically only the difference is the motor is driven by the inverter, not the
inverter device itself.
The inverter that drives an AC motor is called “AC inverter”, and
the one which drives DC motor is called “DC inverter”.
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History of inverter technology
3-1 What is the difference between AC and DC inverter
<What is the difference between AC motor and DC motor?>
Structure of AC motor
Rotor
(Squirrel Cage
made of conductor)
Stator
(coil)
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History of inverter technology
3-1 What is the difference between AC and DC inverter
Principle how AC motor works?
(1) Current goes through the coil on
the stator and the rotating
magnetic field is generated
(1)
(2)
(2) Being induced by the rotating
magnetic field, induced current is
generated on the Squirrel Cage.
(3)
(3) According to the interaction force
Rotating
between current and magnetic field
magnetic field
(Fleming left hand’s law), the Cage
Current
(input from power source)
Stator Coil
Rotor
(Squirrel Cage)
on which the induced current goes
through turns around.
Induced current
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History of inverter technology
3-1 What is the difference between AC and DC inverter
Advantage and disadvantage of AC motor
Advantage
Simple structure
Easy to control
induction current is generated on the cage according tothe rotating
magnetic field, so the rotor will be driven accordingly without
detecting rotor position.
Disadvantage
Less efficiency caused by
> induction current loss
> motor slip
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History of inverter technology
3-1 What is the difference between AC and DC inverter
Advantage and disadvantage of AC motor
What is motor slip?
The principle how the rotor drives is
interaction force between rotating
magnetic field and induction current.
So, it is not necessary to synchronize
the revolution speed of rotating
magnetic field and rotor.
And rotor speed is always slower than
that of rotating magnetic field.
This gap is called “motor slip”.
In general, the rotor speed is 3%
slower than rotating magnetic field.
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History of inverter technology
3-1 What is the difference between AC and DC inverter
Structure of DC motor
Rotor
(made of permanent
magnet)
Stator (coil)
The biggest and only difference is that rotor is made of permanent magnet,
but the principle of the operation is completely different from that of an AC
motor.
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History of inverter technology
3-1 What is the difference between AC and DC inverter
Principle how DC motor works?
(1) Current goes through the coil on
the stator and rotating magnetic
field is generated (same as AC)
S
N
Rotor
(made of permanent magnet)
N
(2) By the interaction of the pole of
the magnet, rotor will turn.
S
Stator (coil)
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History of inverter technology
3-1 What is the difference between AC and DC inverter
Advantage and disadvantage of DC motor
Advantage
Less loss and better efficiency than AC motor because of
> no motor slip
> no induced current loss
Disadvantage
Needs enough knowledge to drive
Rotor position needs to be detected anytime to drive it and stator
coil should be energized accordingly to the rotor position.
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History of inverter technology
3-2 Why the inverter technology evolved from AC to DC?
Demand for more efficient, less energy consumption in air-conditioners
becomes stronger and stronger year by year.
In order to attain better efficiency, it is not enough only to apply (AC)
inverter technology so as to reduce the compressor speed, but also to
reduce energy consumption when In partial load conditions.
DC motor has been known as much more efficient motor than AC, and
its efficiency is roughly double compared to AC.
(it means energy consumption becomes half at the same condition.)
DC inverter technology is a good solution for reducing energy consumption.
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History of inverter technology
3-3 DC PAM inverter
Recently PAM technology is also introduced in order to improve
the efficiency of air-conditioner.
What is “PAM”?
“PAM” is abbreviation of Pulse Amplitude Modulation.
Compared to conventional PWM (Pulse Width Modulation),
booster circuit is added on the converter part to raise up DC
voltage.
Converter part for PWM
AC input
Converter part for PAM
AC input
Booster circuit
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History of inverter technology
3-3 DC PAM inverter
How it works? (voltage waveform)
<PWM>
Height is
stable
Pulse width is adjusted
to control power output.
<PAM>
(at full duty)
At full duty, there are no space
to increase the power
By raising the voltage up, power
output is increased.
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History of inverter technology
3-3 DC PAM inverter
What is the necessity for PAM control?
In short, “in order to apply more efficient DC motor”
Generally speaking, a motor which have larger number of winding on
one slot has better efficiency because it can generate stronger
magnetic field.
However, there is a disadvantage that it cannot accept bigger current
because the diameter of the wire should be thin.
In order to overcome the disadvantage of the motor, by raising input
voltage up, making the total input same without increasing current,
and become possible to drive the compressor at higher torque.
W (Watt) = E (Voltage) x I (Current)
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History of inverter technology
3-4 Vector control DC inverter
How it works? (voltage waveform)
<Conventional PWM>
Pulse width is adjusted
to control power output.
At full load
Non-energized period
In conventional PWM drive, nonenergized period is necessary to
detect rotor position.
<Vector control>
Rotor position can be detected without nonenergized period and inputting appropriate
voltage accordingly in order to create
approximate sinusoidal wave form.
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History of inverter technology
3-4 Vector control DC inverter
Advantage of Vector control
Vector control is a cutting-edge technology of the inverter control in order to
let the compressor give the better performance by generating sinusoidal
current wave form.
① less compressor starting failure
Thanks to the control, it becomes to be able to detect the rotor position correctly,
and it lead to improve compressor starting.
② Downsizing and high efficiency
High revolution operation on high efficiency (high turn motor) compressor became possible
thanks to the sinusoidal wave form drive,
Current wave form comparison
Non-energized period
Rectangular wave form drive
fig 1-1 120deg rectangular wave drive
Sinusoidal wave form drive
fig 1-2 vector control
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History of inverter technology
3-4 Vector control DC inverter
What is the necessity for Vector control?
In short, “in order to apply more efficient DC motor”
This is as same story as applying DC PAM inverter.
Generally speaking, a motor which has a larger number of windings
on one slot has better efficiency because it can generate a stronger
magnetic field.
However, there is a disadvantage in that it cannot accept a bigger
current because the diameter of the winding wire.
In a conventional PWM inverter, there is a non-energized period and
it leads to increase peak current.
In Vector control, there is no non-energized period and it leads to
reduce peak current that can make a more efficient compressor DC
motor
W (Watt) = E (Voltage) x I (Current)
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History of inverter technology
3-5 Which technology is applied to our products?
1) AC inverter (no longer used)
KX2
2) DC inverter
KX4
3) DC inverter with PAM
PAC inverter
(1.5 – 2.5HP)
PAC inverter
(8 – 10HP)
4) DC inverter with Vector control
RAC inverter
PAC inverter
(3 – 6HP)
Which control is applied is decided a balance
between feasibility, cost, and effect.
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