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,
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.