Parker AC890PX Series, Engineering Reference

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C h a p t e r 5 : O p e r a t i n g t h e D r i v e
5-21
AC890PX AC Drive
High Starting Torque
Applications requiring high motor starting torque (greater than 100% of rated torque) need careful setup of the drive voltage
boost feature. Gradually increase the FIXED BOOST parameter in 1% steps until the drive generates sufficient starting
torque.
It is important to use the minimum level of FIXED BOOST necessary to accelerate the load. Using a level of FIXED BOOST
higher than necessary will lead to increased motor heating and increased risk of drive overload.
Setting the FIXED BOOST parameter level too high can also cause the drive current limit feature to operate. If this occurs,
the drive will be unable to ramp up in frequency. The IT LIMITING diagnostic (INVERSE TIME function block) will
indicate TRUE when the inverse time current limit feature is operating. Simply reducing the level of the FIXED BOOST
parameter will remove this problem.
NOTE
Motor torques greater than 100% require high currents to be drawn from the drive. Thus, the CURRENT LIMIT
parameter (CURRENT LIMIT function block) will have to be set accordingly such that the drive current limit feature
will not activate when accelerating the load.
The best motor starting performance can be achieved by setting up the SLIP COMP function block, refer to the Appendix D:
“Programming” - SLIP COMP. Also setting the BASE VOLTS parameter (VOLTAGE CONTROL function block) to
115.4% and the FREQ SELECT parameter (PATTERN GEN function block) to 3kHz, can help to start difficult loads in the
most extreme cases.