Page 115 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

INDUCTION MOTORS

6.4 CHAPTER SIX

(a)

(b)
FIGURE 6.3 (a) Cutaway diagram of a typical small squirrel-cage induction motor.
(Courtesy of MagneTek, Inc.) (b) Cutaway diagram of a typical large squirrel-cage
induction motor. (Courtesy of General Electric Company.)

When the rotor turns at synchronous speed, s 0. When the rotor is stationary, s 1. All
motor speeds fall between these two limits.
The mechanical speed of the rotor shaft can be expressed in terms of the synchronous
speed and slip as
n (1 s)n sync
m

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