Torque adjustment
By default, the torque display does not show the value 0 during encoderless opera-
tion in no-load operation. The reason for this is, among other things, switching fre-
quency-dependent losses in the motor and no-load and friction losses caused by
the application.
In application, however, only the torque at the load is interesting. The mechanical
and system losses should not be included in the display.
If the torque display is to be corrected by this offset, the offset for the selected con-
trol mode (with encoder or encoderless) must first be calibrated for all used switch-
ing frequencies. If a control mode or switching frequency is used for which the
characteristic has not been identified, no compensation is carried out.
Basic procedure of compensation: The drive accelerates step by step within the
speed range parameterized with mo38 torque offset ident config. For the individual
speed values, the torque is measured in static operation and stored as torque off-
set.
For correction, linear interpolation is performed between the identified offset val-
ues. Below the first speed (mo38[1] start speed) the compensation value is linearly
reduced to 0. Above the last speed (mo38[2] end speed) the compensation value is
kept constant.
The identification of the offset characteristic can only be performed in clockwise di-
rection of rotation. An identical offset is assumed for the left direction of rotation.
Offset compensation is effective in motor and regenerative operation.
Activating the offset compensation causes that the torque limits apply to the load
and not to the internal motor torque. In the same way, the actual torque display ap-
plies to the torque on the load and not on the motor.
Therefore, torque limits are increased by the identified offset value and actual tor-
ques are reduced accordingly.
The physical torque limits (e.g. maximum current of inverter and motor, maximum
possible / permissible torque of the motor) remain unaffected by the compensation
characteristic.
The settings of the Velocity Mode (e.g. ramp generator, predefined torque limits)
apply to the measurement routine.
If the drive cannot follow the settings or fluctuates strongly, no identification of the
offset characteristic can be made.
6.2.9.1 Configuration of the torque offset identification
The parameter structure mo38 torque offset ident config defines the speed range
for which the torque offset identification is performed (subindex 1 and 2).
It is also defined whether the offset values are determined on the basis of the mo-
mentary values or of smoothed values (PT1 filter). (Subindex 3 and 4)
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