KEBCO COMBIVERT S4, Applications Manual

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Regulator Adjustment
Section 4 S4 Application Manual
Page 38
4.3.11 Operation at the torque limit
This graph shows the result when the torque limit of the motor is reached during the
acceleration. The actual speed falls behind the set speed with no chance to catch up
since the acceleration torque is limited. As a result the position control increases the set
speed during the constant run to reduce the position deviation. The motor runs at a
speed higher than that set by Pd.07 (maximum speed). This increase in speed is limited
by parameter Pd.03 (maximum setting is 500rpm). As shown in the graph below, the
speed increase was 250rpm.
The torque limit was not active in the deceleration phase since the friction torque assisted
in the stopping. In the event the torque limit is activated during the deceleration, the
system will over shoot and then drive backward at the speed adjusted in Pd.03 until the
deviation is eliminated.
To eliminate these problems in general there are two options. Either lengthen the
acceleration and deceleration until the torque limit is not reached or increase the size of
the motor.
Actual Speed 100 rpm / div P - Speed (CS.00) 400
Set Speed 100 rpm / div I - Speed (CS.01) 50
Torque 35 lb in / div P - Position (Pd.02) 250
Horizontal 100 mSec /div Limit for P-position Pd.03) 250 rpm