Question 4Electricity & Electronics - Assistant Engineer

The correct answer is D) wound-rotor induction motor. In a wound-rotor induction motor, the rotor winding is connected to external resistors or a rheostat. Varying the resistance in the rotor circuit allows the motor speed to be adjusted, which makes the wound-rotor induction motor well-suited for applications that require variable speed operation. The other options are incorrect because: A) synchronous motors do not use a rheostat in the rotor circuit to vary speed, C) squirrel-cage induction motors have a fixed rotor design that cannot be adjusted, and B) regenerative braking is a separate function not related to varying motor speed.