In a wound rotor motor, which component provides the external connection to rotor windings?

• A. A set of insulated windings mounted on the body of the motor
• B. A set of insulated windings recessed into the laminated plates of the rotor with the three free ends brought out and connected to three brass rings mounted on the motor shaft
• C. Brushes
• D. Slip rings

Answer: (D)

In a wound rotor motor, the rotor windings must connect to an external circuit, and that connection is provided by slip rings mounted on the motor shaft. The rotor windings terminate at these rings, and carbon brushes press against them to complete the electrical path to the outside, allowing current to flow into or out of the rotor (often for starting resistance control). The other descriptions either place windings in the wrong location or describe the brushes as the external connection themselves, whereas the slip rings are the actual interface that carries rotor current to the outside world.