Improving the Operation Performance. Omron L7

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Improving the Operation Performance

Reducing the Motor Speed Fluctuation (Slip Compensation Function)

When the load is large, the motor slip also increases and the motor speed decreases. The slip compensation function keeps the motor speed constant, regardless of changes in load. When the motor is operating at the rated load, parameter E2-02 (Motor Rated Slip)

× the slip compensation gain value in parameter C3-01 is added to the output frequency. The function can be used in V/f control or Open Loop Vector control.

Related Parameters

Parameter

No.

C3-01

C3-02

C3-03

C3-04

C3-05

Name

Slip compensation gain

Slip compensation delay time

Slip compensation limit

Slip compensation during regeneration

Output voltage limit operation selection

Factory

Setting

1.0

2000 ms

200%

Change during

Operation

Yes

V/f

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

A -

Closed

Loop Vector (PM)

Adjusting Slip Compensation Gain (C3-01)

If C3-01 is set to 1.0, the slip compensation value at 100% load is equal to the rated slip set in parameter

E2-02.

If necessary (motor speed is too high or too low) adjust the slip compensation gain as follows:

1. With Open Loop Vector control set E2-02 (Motor Rated Slip) and E2-03 (Motor No-load Current). The motor rated slip can be calculated using the values on the motor nameplate and the following formula: slip (Hz) = Motor rated frequency (Hz) –

The motor data can be set automatically using the autotuning function.

2. With V/f control set C3-01 to 1.0.

3. Apply a load and compare the speed reference and the actual motor speed during run with constant speed.

Adjust the slip compensation gain by 0.1 at a time. If the speed is less than the target value, increase the slip compensation gain, if the speed is higher than the target value, reduce the slip compensation gain.

4. Setting C3-01 to 0.0 disables the slip compensation function.

Adjusting Slip Compensation Primary Delay Time Constant (C3-02)

The slip compensation delay time constant is set in ms. The setting value of C3-02 is 2000ms. Normally, there is no need to change these settings. When the slip compensation responsiveness is low, lower the set value.

When the speed is unstable, increase the set value.

Adjusting Slip Compensation Limit (C3-03)

Using parameter C3-03 the upper limit for the slip compensation can be set as a percentage, taking the motor rated slip as 100%.

If the speed is lower than the target value but does not change even after adjusting the slip compensation gain, the slip compensation limit may have been reached. Increase the limit, and check the speed again. Always make sure that the value of the slip compensation limit and reference frequency does not exceed the tolerance of the machine.

The following diagram shows the slip compensation limit for the constant torque range and fixed output range.

Slip compensation limit

Output frequency

E1-06: Base frequency

E1-04: Maximum output frequency

Fig 6.9 Slip Compensation Limit

Enable the Slip Compensation Function During Regeneration (C3-04)

Enables or disables the slip compensation function during regenerative operation. The factory setting is enabled.

Operation Selection when the Output Voltage is Saturated (C3-05)

Generally the Inverter cannot output a voltage that is higher than the input voltage. If in the high-speed range the output voltage reference for the motor (monitor parameter U1-06) exceeds the input voltage, the output voltage becomes saturated, and inverter cannot respond to speed or load changes. This function automatically reduces the output voltage to avoid voltage saturation.

Thereby the speed control accuracy can be maintained even at high speeds (around the rated speed of the motor). By the lowered voltage the current can be around 10% higher compared to the operation without voltage limiter.

Torque Compensation Function Adjustments

The torque compensation function detects a rising motor load, and increases the output torque.

In V/f control the inverter calculates the motor primary loss voltage using the terminal resistance value (E2-

05) and adjusts the output voltage (V) to compensate insufficient torque at startup and during low-speed operation.

The compensation voltage is calculated by the calculated Motor primary voltage loss

× parameter C4-01.

In Open Loop Vector control the motor excitation current and the torque producing current are calculated and controlled separately. The torque compensation affects the torque producing current only.

The torque producing current is calculated by the calculated torque reference

× C4-01.

Related Parameters

Parameter

No.

Name

C4-01

C4-02

Torque compensation gain

Torque compensation delay time constant

Factory

Setting

Change during

Operation

1.00

2000 ms

Yes

V/f

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Adjusting Torque Compensation Gain (C4-01)

Normally, there is no need to change this setting. If adjustments are necessary do the following:

Open Loop Vector control

•

If the torque response is slow increase the set value.

•

If vibrations occur decrease the set value.

V/f control

•

If the cable is very long, increase the set value.

•

If the motor capacity is smaller than the Inverter capacity (max. applicable motor capacity), increase the set value.

If the motor vibrates, reduce the set value.

Setting precautions

•

Adjust this parameter so that the output current during low-speed rotation does not exceed the Inverter rated output current range.

•

Adjust the value in steps of 0.05 only.

Adjusting the Torque Compensation Delay Time Constant (C4-02)

The factory setting depends on the control mode. The factory settings are:

•

V/f control: 200 ms

•

Open loop vector control: 20 ms

Normally, there is no need to change this setting. If adjustments are necessary do the following:

•

If the motor vibrates or if overshooting occurs, increase the set value.

•

If the torque response is slow, decrease the set value.

Starting Torque Compensation Function (C4-03 to C4-05)

A starting torque compensation can be applied to speed up the torque establishment at start in Open Loop Vector control.

Related Parameters

Parameter

No.

Name

Factory

Setting

Change during

Operation

V/f

C4-03

C4-04

C4-05

Starting torque compensation value (forward direction)

Starting torque compensation value (reverse direction)

Starting torque compensation time constant

It works like shown in the following diagram.

Forward (Reverse) Run command

OFF

Time constant: C4-05

Time constant: C4-02

C4-03 (forward)

C4-04 (reverse, negative polarity)

Torque compensation volume

0.0

1 ms

C4-05 x 4

E1-09

Output frequency

E1-09

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Fig 6.10 Time Chart for Starting Torque Frequency

When this function is used, the following should be considered:

•

Both values, C4-03 and C4-04 have to be set.

•

The compensation works for motoring operation only. It can not be used for regenerative operation.

If the starting torque compensation is used and a large shock is generated at the start, increase the starting torque compensation time constant (C4-05)

The function can be not be used unrestricted for elevators, since the load is not know before the start.

Automatic Speed Regulator (ASR) (Closed Loop Vector only)

In Closed Loop Vector control the automatic speed regulator (ASR) adjusts the torque reference in order to eliminate the deviation between the speed reference and the measured speed (PG feedback). The ASR settings determine the motor speed accuracy and stability.

Fig 6.11

shows the ASR structure.

Frequency

Reference

Motor

Speed

C5-01/03/09

C5-02/04/10

C5-08

I-Limit

Delay

Time

Torque

Limits

Torque

Reference

Fig 6.11 ASR Block Diagram

Related Parameters

Parameter

No.

C5-01

C5-02

C5-03

C5-04

C5-07

C5-08

C5-09

ASR proportional (P) gain 1

ASR integral (I) time 1

Name

ASR proportional (P) gain 2

ASR integral (I) time 2

ASR switching frequency

ASR integral limit

ASR proportional (P) gain 3

Factory

Setting

Change during

Operation

40.00

12.00

0.500 sec.

0.300 sec.

20.00

6.00

0.500 sec.

0.0 Hz

2.0%

400%

40.00

12.00

0.500 sec.

0.300 sec.

5.00

Yes

V/f

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

C5-10

C5-11

ASR integral (I) time 3

ASR gain for encoder offset tuning

ASR Gain and Integral Time Adjustments

There are three sets of ASR gain and integral times, one for the maximum speed (C5-01/02), one for the minimum speed at acceleration (C5-03/04) and one for the minimum speed at deceleration (C5-09/10) (see the figure below).

ASR P, I

C5-03 ASR Gain 2

C5-04 ASR I time 2

C5-09 ASR Gain 3

C5-10 ASR I time 3

C5-01 ASR Gain 1

C5-02 ASR I time 1

C5-01 ASR Gain 1

C5-02 ASR I time 1

0Hz C5-07 E1-04

Speed

During Acceleration

0Hz C5-07 E1-04

Speed

During Deceleration

When the ride starts with the nominal speed selected, the ASR P gain and I time change from C5-03/04 to C1-

01/02 at nominal speed. When the speed selection changes to leveling speed, the P gain and I time are changed from C1-01/02 to C1-09/10.

If parameter d1-18 is set to 0 or 3, the nominal/leveling speed detection function must be enabled (refer to

page 6-6, Nominal / Leveling Speed Detection with Multi Speed Inputs

) in order to use the ASR 3 settings.

Adjusting ASR Proportional Gains (C5-01/03/09)

The gain settings determine how much the ASR input (= speed deviation) is amplified in order to eliminate the speed deviation. The responsiveness of the ASR is increased when the gain setting is increased but oscillations can occur when this setting is too high.

•

Increase C5-03 if the ASR is too slow at start or very low frequencies, decrease it if vibrations occur.

Increase C5-01 if the ASR is too slow at high speed or if overshooting occurs at speed changes in the high speed area, decrease it if vibrations occur

•

Increase C5-09 if ASR is slow in the low speed area or if undershooting occurs at leveling speed. If vibrations occur in the low speed area during deceleration decrease the value.

Adjusting ASR Integral Times (C5-02/04/10)

The integral time determines how fast the ASR input is integrated in order to eliminate the speed deviation.

Lengthening the integral time lowers the responsiveness of the ASR and the speed accuracy when the load changes suddenly. Oscillations can occur if the setting of this value is too low.

•

Decrease C5-02 if a speed deviation is compensated too slow at high speeds or if overshooting occurs at speed changes in the high speed area. Increase it if vibrations occur.

Decrease C5-04 if a speed deviation is compensated too slow at start or at very low frequencies. Increase it if vibrations occur.

Decrease C5-10 if a speed deviation is compensated too slow in the low speed area at leveling or if undershooting occurs at leveling speed. If vibrations occur in the low speed area during deceleration increase the value.

Adjusting the ASR Gain for Encoder Offset Tuning (C5-11)

During the encoder offset tuning for Hiperface y

or EnDat uses the value of parameter C5-11 as ASR gain.

•

Decrease C5-11 if vibrations occur during the tuning and repeat the tuning.

Increase C5-11 if the accuracy of the tuning is low and repeat the tuning.

Stabilizing Speed (Automatic Frequency Regulator) (Open Loop Vector)

The speed feedback detection control (AFR) function controls the stability of the speed when a load is suddenly applied or removed. It calculates the amount of speed fluctuation using the torque current (Iq) feedback value and compensates the output frequency with the amount of fluctuation. f ref f out

I q

Fig 6.12 AFR Control Loop

Related Parameters

Parameter

No.

n2-01 n2-02

Name

Factory

Setting

Change during

Operation

Speed feedback detection control (AFR) gain 1.00

Speed feedback detection control (AFR) time constant 1 50 ms

V/f

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Setting the AFR Gain (n2-01)

Normally there is no need to change this setting. If adjustments are necessary, do the following:

•

If hunting occurs increase n2-01.

•

If the response is too low, decrease n2-01.

Adjust the setting by 0.05 at a time while checking the response.

Setting the AFR Time Constants (n2-02)

Parameter n2-02 sets the time constant for the AFR control. If adjustments are necessary,

•

Increase the setting if hunting occurs or the speed is over-compensated

•

Decrease the setting if the compensation is too slow

Normally there is no need to change this setting.

Inertia Compensation (Closed Loop Vector Only)

Feed Forward Control is used to eliminate the speed overshoot or undershoot by compensating inertia effects.

The function can be enabled using parameter n5-01.

Related Parameters

Parameter

No.

n5-01 n5-02 n5-03 n5-05

Name

Feed forward control selection

Motor acceleration time

Feed forward proportional gain

Motor acceleration time auto tuning

Factory setting

0 kVA dependent

1.0

Change during operation

V/f

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Adjustments

Motor acceleration time (n5-02)

The motor acceleration time n5-02 is the time, which is needed to accelerate the to the rated speed with the rated torque of the motor. The time can be estimated like follows:

•

Make the general setup (V/f pattern, Motor Setup, etc.)

Balance the elevator (car in middle position, Car weight = Counter weight)

•

Set the torque limits to 100% using the L7- parameters.

Set the acceleration time very short (the inverter must reach the torque limit very fast).

Start in any direction and measure the time from zero speed to top speed.

Set this time in n5-02.

Feed Forward Gain (n5-03)

This value usually has not to be changed.

•

Increase the gain to improve the responsiveness to the speed reference.

•

Decrease the gain if vibrations occur.

Motor Acceleration Time Auto Tuning (n5-05)

The motor acceleration time n5-02 can be calculated by an auto tuning function. It sets the internal acceleration time to 0.1 sec., disabled the S-curve and sets the torque limit to 100%. After that a start in each direction must be performed. The measured acceleration times are used to calculate the n5-03 value.

Before the n5-02 auto tuning is performed, the motor data autotuning and the general setup should have been finished. Do the tuning with the factory settings for the n5- parameters.

Use the following procedure:

1. Set n5-05 to “1” to enable the auto tuning and go back to the speed reference display.

2. Set the base block input.

3. Enable the inspection speed input. “FFCAL” will blink in the display to signalize that the calculation is active.

4. Set an UP command. The inverter will accelerate the motor up to the nominal speed. Release the UP command a few seconds after the top speed has been reached.

5. When the motor has stopped, apply a DOWN command. The inverter will accelerate the motor in the opposite direction to the nominal speed. Release the DOWN command a few seconds after the nominal speed has been reached.

To abort the tuning set parameter n5-05 to “0”.

IMPORTANT

1. The order of giving the UP or DOWN command has no influence.

2. n5-01 should not be changed from the factory value for the tuning.

3. After the run in both directions is finished, parameter n5-05 is automatically set back to “0”.

4. The autotuning will be performed only if the inspection speed input is set.

5. Do not change the mechanical constants (load, inertia) between the runs.

Automatic Current Regulator (ACR) Tuning

The ACR controller consists of two PI control loops, one for the d-axis and one for the q-axis current. The

ACR parameters can be accessed in the Closed Loop Vector control for PM mode only.

Related Parameters

Parameter

No.

n8-29 n8-30 n8-32 n8-33

Name

ACR q axis proportional gain

ACR q axis integral time

ACR d axis proportional gain

ACR d axis integral time

Factory setting

1000 rad/s

10.0 ms

1000 rad/s

10.0 ms

Change during operation

V/f

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Adjustments

Normally there is no need to change these values. However, if short cycle vibrations occur which can’t be eliminated by the ASR controller setup, it might help to adjust ACR values like follows:

•

If the motor generates very strange high frequency noise (not carrier frequency related), reduce both ACR gains (n8-29 and n8-32) for the same value. If the gain is reduced too much, the performance will be reduced.

If vibrations occur, reduce both integral times (n9-30 and n9-33) for the same value.

A/D Conversion Delay Time Tuning

The A/D conversion delay timer sets a delay for the current signal A/D conversion.

Related Parameters

Parameter

No.

n9-60

Name

Current signal A/D conversion delay time

Factory setting

0.0 µsec.

Change during operation

V/f

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Adjustments

Normally an adjustment is no need to change this value. However, if cyclic oscillations like shown in

Fig 6.13

occur during constant speed run, the A/D conversion delay can be increased in order to eliminate the vibrations.

Torque Signal

Motor Speed

Fig 6.13 Oscillations caused by bad A/D conversion adjustment

Improving the Leveling Accuracy by Leveling Speed Slip Compensation

This function can be used in V/f and Open Loop Vector control to improve the leveling accuracy by compensating the motor slip influence at leveling speed.

The inverter measures the current level or torque reference S2-05 sec. after the speed-agree condition (acceleration finished) for the time set in S2-06 and calculates the average value to estimate the load. This value is

used for the calculation of slip which is added to the speed reference at leveling speed (see

Fig 6.14

S2-05 S2-06

Speed reference is increased or decreased depending on measured load

Fig 6.14 Slip Compensation Working Principle

Related Parameters

Parameter

No.

S2-01

S2-02

S2-03

S3-05

S3-06

S2-07

Name

Motor Rated rpm

Slip Compensation Gain at Motoring

Slip Compensation Gain at Regenerating

Slip Compensation Torque Detection Delay

Slip Compensation Torque Detection Time

Slip Compensation primary Delay Time

Factory setting

1380rpm

0.7

1.0

1.0 sec.

0.5 sec.

200ms

Change during operation

V/f

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Adjustments

The Slip compensation values can be set separately for motoring and regenerative operation. Before adjusting this function the general setup should have been done (Motor Setup, V/f pattern, Speeds, ASR settings etc.).

To adjust the Slip compensation function do the following in motoring and regenerative mode:

•

Set the motor speed in S2-01 if V/f control is used.

Try to measure the actual motor speed during leveling.

•

If the motor speed is lower than the leveling speed reference increase S2-02 in motoring mode or decrease

S2-03 in regenerative mode.

If the motor speed is higher than the leveling speed reference decrease S2-02 in motoring mode or increase

S2-03 in regenerative mode.

S2-05 and S2-06 should not be modified, except if the stop accuracy is poor and the constant speed time after the speed agree is shorter than S2-05 + S2-06.

Field Forcing

The field forcing function controls the motor flux and compensates the flux establishment delay of the motor.

Thereby it improves the motor responsiveness to changes in the speed reference or the load.

Field forcing is applied during all operation conditions except DC Injection.

Using parameter d6-06 a field forcing limit can be applied. A setting of 100% is equal to the no-load current set in parameter E2-03.

Related Parameters

Parameter

No.

d6-03 d6-06

Field forcing selection

Field forcing limit

Name

Factory

Setting

Change during

Operation

400%

V/f

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Adjusting the DC Injection Current

The DC current injection is used in V/f and Open Loop Vector Control in order to hold the motor when the brake is opened or closed.

Related Parameters

Parameter

No.

S1-02

S1-03

S1-17

S1-18

Name

DC injection current level at start

DC injection current level at stop

DC injection gain at stop in regenerative operation

DC injection gain at stop in motoring operation

Factory

Setting

Change during

Operation

50%

100%

20%

V/f

Control Methods

Open

Loop

Vector

Closed

Loop

Vector

Closed

Loop

Vector

(PM)

Adjusting the DC Injection Current Levels (S1-02/03)

Two different DC injection current levels can be set to start and stop.

•

Increase the corresponding set value when the holding torque during brake open or brake close is too low.

•

Decrease the corresponding set value when the holding torque is enough but e.g. the DC injection noise is too loud.

Adjusting the DC Injection Gains for Stop (S1-17/18)

In Open Loop Vector control two different DC injection current gains for motoring and regenerative operation can be adjusted in order to improve the stopping behavior. The gains are related to the S1-03 set value. The function can be used to equalize jerk effects if the DC injection is too low with motoring load and too high with regenerative load. The load condition (regenerative or motoring) is detected when the inverter is running at another speed than the leveling speed.

•

If the DC injection is ok with motoring load but not with regenerative load adjust parameter S1-17.

If the DC injection is ok with regenerative load but not with motoring load adjust parameter S1-18.