Question
The magnetic field produced in the air gap of an induction motor by the stator windings is given by $B=B_{m} \cos (\omega t-2 \theta),$ in which $\theta$ is angular displacement in the counterclockwise direction as illustrated in Figure 17.4 on page $814 .$ How many poles does this machine have? Given that the frequency of the source is $50 \mathrm{Hz}$, determine the speed of rotation of the field, Does the field rotate clockwise or counterclockwise? Repeat for a field given by $B=B_{m} \cos (\omega t+3 \theta)$.
Step 1
Here, $\theta$ is the angular displacement in the counterclockwise direction. The number of poles is double the value of $\theta$, so the number of poles of this machine, let it be $p$, is $2 \times 2 = 4$. Show more…
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