Chapter 54, Problem 1SQ

To determine

Write the formula for finding the speed of an AC squirrel cage induction motor.

Answer to Problem 1SQ

The formula to find the speed of an AC squirrel cage induction motor is $\underset{\_}{\frac{60\times \text{Hertz}}{\text{Pair of poles}}}$.

Explanation of Solution

Discussion:

The squirrel cage induction motor’s speed depends on the frequency of the supply current and number of motor’s poles.

Write the expression to find the speed of an AC squirrel cage induction motor as follows:

$\text{RPM}=\frac{60\times \text{Hertz}}{\text{Pair of poles}}$ (1)

Here

Hertz is the unit of frequency of supply current.

Rewrite the expression in Equation (1) in terms of number of poles of the motor as follows:

$\text{RPM}=\frac{120\times \text{Hertz}}{\text{Number of poles}}$

Conclusion:

Thus, the formula for finding the speed of an AC squirrel cage induction motor is $\underset{\_}{\frac{60\times \text{Hertz}}{\text{Pair of poles}}}$.