A 4 pole 50 Hz induction motor is running at 1300 rpm. Find the speed of stator magnetic field with respect to the rotor?
The synchronous speed (Ns) of an induction motor can be calculated using the formula:
Ns = (120 * f) / p
where f is the frequency of the power supply, and p is the number of poles of the motor.
For the given motor with 4 poles and a power supply frequency of 50 Hz, the synchronous speed is:
Ns = (120 * 50) / 4 = 1500 rpm
The actual speed of the motor is 1300 rpm, which means that it is running at a speed slightly below the synchronous speed.
The difference between the synchronous speed and the actual speed is called slip (s). The slip can be calculated using the formula:
s = (Ns - N) / Ns
where N is the actual speed of the motor.
Substituting the values, we get:
s = (1500 - 1300) / 1500 = 0.133
The slip is 0.133 or 13.3%.
The speed of the stator magnetic field with respect to the rotor is given by:
Ns - N = 1500 - 1300 = 200 rpm