Regenerative Braking of Induction Motors

Author: E.E. Kimberly

If one line wire of a three-phase induction motor be opened while the motor is running at full load, the motor will continue to run. However, the current per terminal and the slip will be greater than normal, and the motor will be quickly overheated. For this reason, overload protection should be provided in at least two lines in order that unsupervised, unintentional, single-phase operation cannot continue if it should occur.

A polyphase motor connected to a single-phase power source has no starting torque unless provided with special phase-splitting starting equipment. If started by such a starter or by some external means, the motor will carry about 60 per cent of its normal rated load with about normal slip and normal temperature rise. The maximum torque will be only about 30 per cent of normal.