A 3-phase induction motor with 6 poles is running in its normal operating range. The motor is operating at a slip of 0.1 while rotating at a speed of 1900 rpm, what is the electrical frequency used to power the motor?

Electrical frequency = 105.55 Hz

Explanation:

Given, number of poles, p = 6

rotor speed, N = 1900 rpm

slip, s = 0.1

From the formula,

slip, s = (Ns - N) / Ns where Ns = synchronous speed

Making Ns subject of the formula,

Ns = N / (1 - s)

Hence, Ns = 1900 / (1 - 0.1) = 2111.11 rpm

From synchronous speed, Ns = 120f / p

We have that frequency f = Ns * p / 120

= 2111.11 * 6 / 120

Electrical frequency = 105.55 Hz