The nameplate on a 400V 35kW 50Hz fourpole induction motor i

The nameplate on a 400-V, 35-kW, 50-Hz, four-pole induction motor indicates that its speed at rated load is 1458 r/min. Assume the motor to be operating at rated load. What is the slip of the rotor? What is the frequency of the rotor currents in Hz?

Solution

Slip of an induction motor varies in the same proportion as the load torque, rotor resistance, and the voltage frequency of stator. The induction speed of the wounded motor can be controlled by increasing the slip. The traditional way of increasing slip is by subjecting the rotor circuit to increased resistance. Lower horsepower motors have higher slip as compared to high horsepower motors since small motors have the tendency to generate greater resistance