Question

Can a drive replace a softstart?

Answer

Yes, softstarts are used for reduced torque starting and stopping of standard 3 phase induction motors (E.G. centrifugal pumps, compressors, ball mills, jar mills, fans/blowers and saws.) If the motor is not adequately protected from sudden changes in rotational torque associated with starting and stopping, the current will be excessive to the system and the motor will surge, causing detrimental effects to all the equipment linked to it. Over the long-term this leads to increased Over-current tripping and increased mechanical wear of gearboxes, clutches, transmission, and conveyor systems.

A drive has all of the features inherent to it as a drive and can be programmed to handle reduced toque loads. The amazing thing is that they are about the same cost.

ANSI/IEEE Std. 141-1993 (Red Book) provides a comparison of different reduced voltage starting methods. An electronic softstart or VFD, although not listed, would have similar characteristics to the autotransformer starter.
Note: It is preferred that the motor is of the inverter duty type or have an inverter duty insulation rating (F or higher); The applied voltage at the motor's base speed will still be of the PWM signature, not a true sinusoidal waveform. Heating issue may occur if the motor's insulation rating is not suitable.

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FAQ Subcategory: None

This item was last updated on 2007-09-25
Document ID: 773

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