Electric motor (squirrel cage)

A squirrel-cage motor is the standard three-phase asynchronous (induction) AC motor used for almost all shipboard auxiliaries: pumps, fans, compressors, and separators. Its rotor is a laminated core with shorted aluminum or copper bars forming a cage, with no brushes or windings, so it is rugged and low-maintenance. The rotating stator field induces rotor current and torque, and the rotor runs slightly below synchronous speed, the slip. Direct-on-line starting draws six to eight times rated current, so star-delta or soft starters and variable-frequency drives limit inrush and give speed control where needed.