Question

An induction motor develops rated torque with a slip of 3.5% when the rotor is cold. If the rotor resistance is 20% higher when the motor is at normal running temperature, at what slip will it develop rated torque?

Answer 1

The motor will develop rated torque at a slip of 4% when the rotor is at normal running temperature.

Step-by-step explanation:

When the rotor is at normal running temperature and the rotor resistance is 20% higher, we can calculate the new resistance using:

New Resistance = Resistance when cold * (1 + 0.2)

New Resistance = 20 * (1 + 0.2) = 24 ohms

To find the slip at which the motor will develop rated torque, we can use the formula:

Slip = (Rotor Resistance - Rotor Winding Resistance) / Rotor Winding Resistance

Slip = (24 - 20) / 20 = 4%

Therefore, the motor will develop rated torque at a slip of 4% when the rotor is at normal running temperature.