Which rotor type uses external connections through slip rings?

Which rotor type uses external connections through slip rings?

• A. Wound rotor
• B. Squirrel cage rotor
• C. Permanent magnet rotor
• D. Hydraulic rotor

Answer: (A)

Access to rotor windings via slip rings is a feature of a wound rotor induction motor. In this type, the rotor winding is connected to external circuits through slip rings and brushes, allowing external resistance to be placed in the rotor circuit to control starting torque and speed. The other rotor types don’t use slip rings: a squirrel cage rotor has bars shorted by end rings with no external access; a permanent magnet rotor uses embedded magnets for excitation; and a hydraulic rotor corresponds to a motor driven by hydraulic fluid rather than electrical connections. So, the wound rotor is the only type that uses external connections through slip rings.

Access to rotor windings via slip rings is a feature of a wound rotor induction motor. In this type, the rotor winding is connected to external circuits through slip rings and brushes, allowing external resistance to be placed in the rotor circuit to control starting torque and speed. The other rotor types don’t use slip rings: a squirrel cage rotor has bars shorted by end rings with no external access; a permanent magnet rotor uses embedded magnets for excitation; and a hydraulic rotor corresponds to a motor driven by hydraulic fluid rather than electrical connections. So, the wound rotor is the only type that uses external connections through slip rings.