Soft starting of medium voltage induction motors using a resistive type fault current limiter

This paper proposes using a fault current limiter (FCL) for soft starting of induction motors (IMs). The base of this approach is on the primary resistance starting method. The proposed FCL which is installed at the beginning of an industrial feeder helps to soft starting of induction motors by controlling the current during the starting process. The current of motors starting is controlled by inserting a resistance to the current path. Using this method not only reduces the stresses on both motor's windings and power system equipments by controlling the magnitude of starting current, but also suppresses motor torque pulsations. In addition, it restores voltage of point of common coupling (PCC) and helps to other loads of power system. Control strategy of the proposed structure is presented and analytic analyses are performed in detail. Simulation results using PSCAD/EMTDC software are involved to validate the effectiveness of this structure for soft start up of IMs.