Question 9.16: A 50 Hz, induction motor wound for pole-amplitude modulation...

Electric Machines [EXP-57611]

A 50 Hz, induction motor wound for pole-amplitude modulation has 20 initial poles and the modulating function has 8 poles. At what two speeds will the motor run?

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P=20, \quad P_{M}=8

P_{1}=20-8=12

P_{2}=20+8=28

From Eq. (9.81) $P_{M} / P=\left(1-\frac{3 n}{r}\right)$

P_{M} / P=\frac{8}{20}=\frac{2}{5}=\left(1-\frac{3 n}{r}\right) ; \quad n=1, \quad r=5

Hence $P_{1}$ poles are suppressed

Speed (20 poles) $=\frac{20 \times 50}{20}=300 rpm$

Speed (28 poles) $=\frac{20 \times 50}{28}=214.286 rpm$

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