A wound-rotor motor, also known as slip ring-rotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. Adjusting the resistance allows control of the 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.
Advantages
• High starting torque with relatively low inrush current. • Strong running torque and good speed regulation. • Wide speed-control range without complex power electronics. • Stable behaviour under load and good overload tolerance. • Effective efficiency at rated speed. • Suitable for certain gearless elevator systems when built with higher pole counts, though at the cost of size and weight. • Can run cooler than squirrel cage motors due to the absence of enclosure. ==Disadvantages==
Disadvantages
• Slip rings require regular maintenance and add mechanical complexity. • More mechanical and acoustic noise, especially during start-up under load. • Generally lower efficiency than squirrel-cage motors. • Larger physical size for a given power rating. • Not fully enclosed, increasing exposure to moisture and dust and limiting use in hazardous or damp environments. • Often displaced in modern applications by induction motors with variable-frequency drives or permanent-magnet synchronous motors. ==See also==