Power Quality and Drives LLC

Ride-Through on Power Sag or Power Loss
Copyright © 2008 Francis J. Martino

Rotary power supplies for use with variable frequency drives and other equipment are available that will allow ride-through of the equipment for up to five seconds after power sag or power loss.

The few seconds of ride-through will allow equipment to continue running during the time required for either restoration of power by the utility or to allow for an orderly shut down of your equipment with the intent of keeping machinery or production material from being damaged or personnel from being harmed.

The following information is needed for selection of the Variable frequency drive and rotary power supply:

All of the nameplate information given on the motor to include speed, voltage, full load ampere, service factor ampere, and NEMA Design or percent slip of the motor. Type of driven machine - pump, conveyor, web processing, extruder, etc.

If the load is a pump, is it a centrifugal pump or a positive displacement (piston type) pump?

Will the drive be used for variable speed, constant pressure or constant flow, etc.?

Will the motor be operating in the service factor range? Enclosure Type is dependant upon the environment: clean and dry (Type 1), dust or oil drip (Type 12), water drip (Type 3R), water splash (Type 4).

Will a bypass contactor be needed to allow the driven motor to operate directly from either the rotary power supply or the utility in the event of Drive failure?

Will the start and stop operation of the drive be determined by keypad operation or remote pushbuttons or contacts? Length of motor leads from the drive to the motor.

Power Quality and Drives LLC
P.O. Box 83
Middlebury, CT  06762
Phone: (203) 217-2353
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