Chapter 36, Problem 1RQ

To determine

Synchronous speed.

Explanation of Solution

Given information:

Number of poles per phase, $P=6$.

Frequency of the supply, $f=20\text{ Hz}$.

Calculation:

The synchronous speed is given by the formula:

  $\begin{array}{c}s=\frac{120f}{P}\\ =\frac{120\times 20\text{Hz}}{6}\\ =400\text{ RPM}\end{array}$

Thus, the synchronous speed of the motor is $400\text{ RPM}$.