Question

A slip-ring induction motor is expected to be started by adding extra resistance in the rotor circuit. The benefit that is derived by adding extra resistance in the rotor circuit in comparison to the rotor being shorted is

• A. The starting torque would be higher.
• B. The power factor at start will be lower.
• C. The starting current is higher.
• D. The losses at starting would be lower.

Hint:

In slip-ring induction motors, adding resistance to the rotor circuit increases the starting torque, helping in smoother motor startup.

Answer 1

The Correct Option is A

Adding extra resistance to the rotor circuit increases the starting torque in a slip-ring induction motor. This is because the additional resistance helps to improve the torque during the start-up phase.

Step 1: Option (A) is correct as adding resistance increases the starting torque.

Step 2: Option (B) is incorrect because adding resistance improves the power factor at start.

Step 3: Option (C) is incorrect because adding resistance reduces the starting current.

Step 4: Option (D) is incorrect because adding resistance results in higher losses during starting.

Final Answer: (A) The starting torque would be higher.