Operating Instructions

Descriptions of Parameter Settings
Descriptions of Parameter Settings
195 | 443
Pr.
Explanation
Settings
Default
07-26
Torque compensation gain (V/F
and SVC control mode)
IM: 0 to 10 (when Pr.05-33 = 0)
PM: 0 to 5000 (when Pr.05-33 = 1 or 2)
1
07-71
Torque compensation gain (motor
2)
IM: 0 to 10 (when Pr.05-33 = 0)
PM: 0 to 5000 (when Pr.05-33 = 1 or 2)
1
07-73
Torque compensation gain (motor
3)
IM: 0 to 10 (when Pr.05-33 = 0)
PM: 0– to 000 (when Pr.05-33 = 1 or 2)
1
07-75
Torque compensation gain (motor
4)
IM: 0 to 10 (when Pr.05-33 = 0)
PM: 0 to 5000 (when Pr.05-33 = 1 or 2)
1
With a large motor load, a part of the drive output voltage is absorbed by the stator winding resistor; therefore, the
air gap magnetic field is insufficient. This causes insufficient voltage at motor induction and results in excessive
output current but insufficient output torque. Auto-torque compensation can automatically adjust the output voltage
according to the load and keep the air gap magnetic fields stable to get the optimal operation.
In the V/F control, the voltage decreases in direct proportion with decreasing frequency. The torque decreases at
low speed because of a decreasing AC resistor and an unchanged DC resistor. The auto-torque compensation
function increases the output voltage at low frequency to get a higher starting torque.
When the compensation gain is set too high, it may cause motor over-flux and result in a too large output current of
the drive, motor overheating or trigger the drive’s protection function.
Pr.
Explanation
Settings
Default
07-27
Slip compensation gain
(V/F and SVC control mode)
0.00 to 10.00
0.00
(Default value
is 1.00 in SVC
mode)
07-72
Slip compensation gain
(motor 2)
0.00 to 10.00
0.00
(Default value
is 1.00 in SVC
mode)
07-74
Slip compensation gain
(motor 3)
0.00 to 10.00
0.00
(Default value
is 1.00 in SVC
mode)
07-76
Slip compensation gain
(motor 4)
0.00 to 10.00
0.00
(Default value
is 1.00 in SVC
mode)
The induction motor needs constant slip to produce electromagnetic torque. It can be ignored at higher motor
speeds, such as rated speed or 2–3% of slip.
However, during the drive operation, the slip and the synchronous frequency are in reverse proportion to produce
the same electromagnetic torque. The slip is larger with the reduction of the synchronous frequency. Moreover, the
motor may stop when the synchronous frequency decreases to a specific value. Therefore, the slip seriously
affects the motor speed accuracy at low speed.
In another situation, when you use an induction motor with the drive, the slip increases when the load increases. It
also affects the motor speed accuracy.
Use this parameter to set the compensation frequency, and reduce the slip to maintain the synchronous speed
when the motor runs at the rated current in order to improve the accuracy of the drive. When the drive output
current is higher than Pr.05-05 (No-load Current for Induction Motor 1 (A)), the drive compensates the frequency
according to this parameter.