SAGAR SINGH - IIT DELHI
Last Activity: 13 Years ago
Dear student,
A slip ring motor or wound-rotor motor is a type of induction motoe. The rotor windings are connected to a slip ring which makes it different from the squireel cage motor. The rotor can be connected to external resistances, which allows controlling the speed and speed/torque characteristic of the motor. Wound-rotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit; as the motor accelerates, the resistance can be decreased.
The rotor of the slip ring motor has more windings than a squirrel-cage rotor so that induction voltage is higher and the current for the same field strength lower. During the start-up a typical rotor has 3 poles connected to the slip ring. Each pole is wired in series with a variable power resistor. When the motor reaches full speed the rotor poles are switched to short circuit becoming a standard squirrel-cage motor. During start-up the resistors reduce the field strength in the stator.