Programming
Page
D-70
890CS Common Bus Supply - Frames B & D; 890CD Common Bus Drive and 890SD Standalone Drive - Frames B, C & D
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INVERSE TIME
SETUP::MOTOR CONTROL::INVERSE TIME
Designed for all Motor Control Modes, except PMAC control mode.
The purpose of the inverse time is to automatically reduce the drive current limit in response to prolonged overload conditions.
As the motor current exceeds the AIMING POINT level, the excess current is integrated. Motor current is allowed to flow at
the CURRENT LIMIT (refer to the CURRENT LIMIT function block) for a period defined by the DELAY parameter. At this
point the inverse time current limit is ramped down from the CURRENT LIMIT. The rate at which the inverse time current
limit is ramped to the AIMING POINT is defined by DOWN TIME.
Once the overload condition is removed, the inverse time current limit level is ramped back toward the CURRENT LIMIT at a
rate determined by the UP TIME.
In Quadratic Torque mode, the allowed overload is reduced to 110.0 % for 60.0 s before inverse time current limit action
occurs.
Parameter Descriptions
AIMING POINT
PREF: 84.01
Default: 105.00 %
Range: 50.00 to 150.00%
Determines the final level of the inverse time current limit after a period of prolonged motor overload
DELAY
PREF: 84.02
Default: 60.0 s
Range: 5.0 to 60.0s
Determines the maximum allowed overload duration for 150.0 % motor current (110.0% in QUADRATIC TORQUE mode)
before inverse time current limit action is taken.
DOWN TIME
PREF: 84.03
Default: 10.0 s
Range: 1.0 to 10.0s
Determines the rate at which the inverse time current limit is ramped to the AIMING POINT after a period of prolonged
overload.
