High Starting Torque - Parker AC890 Product Manual

Operating the 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.
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Page 890SD (Standalone) Drive: Frame G, H & J