Page 144 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

SPEED CONTROL OF INDUCTION MOTORS

SPEED CONTROL OF INDUCTION MOTORS 7.11

FIGURE 7.12 The nameplate of a typical high-efficiency induction motor.
(Courtesy of MagneTek, Inc.)

The voltage limit is based on the maximum acceptable magnetization current flow because
as the voltage increases, the iron becomes more saturated and the magnetization current
increases. A 60-Hz induction motor can be used on a 50-Hz power system only if the voltage
rating is decreased by the same proportion as the decrease in frequency. The current limit
is based on the maximum acceptable heating in the motor’s windings. The power limit is
determined by the combination of the voltage and current ratings with the power factor
and efficiency.

REFERENCE

1. S. J. Chapman, Electric Machinery Fundamentals, 2d ed., McGraw-Hill, New York, 1991.

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