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Menu 5

Unidrive SP Advanced User Guide 129

Issue Number: 10 www.controltechniques.com

The level of slip compensation is set by the rated frequency and rated speed parameters. Slip compensation is only enabled when this parameter is

set to 1 and Pr 5.08 is set to a value other than zero or synchronous speed.

When the flux in the motor is reduced below its rated level the level of torque producing current required for a given amount of shaft torque is higher

than the rated level. In speed control the compensation prevents gain reduction at higher speeds. In torque control the compensation maintains the

torque at the correct level for a given torque demand. In some applications using speed control it may be desirable to have a reduction of gain as the

motor flux is reduced to maintain stability. If this is required Pr 5.28 should be set to one. It should be noted that although field weakening is possible

in servo mode, gain compensation is not applied in this mode.

The rated level of flux in most induction motors causes saturation. Therefore the flux against flux producing current characteristic is non-linear. The

effects of saturation are to cause a step increase in torque when operating in torque mode as the speed increases into the field weakening region.

5.27 Enable slip compensation

Drive modes Open-loop

Coding