Damage analysis of internal faults in flux concentrating permanent magnet motors.

Abstract

It is the purpose of the proposed research to develop a digital computer simulation model to study the effects of an internal fault in a large permanent magnet ac synchronous motor. Permanent magnet motors are being considered as an alternative for ships with electric propulsion systems. In an electric propulsion system a large motor will be directly connected to a propulsion shaft. A windmilling shaft will continue to turn the rotor of the propulsion motor after the motor has been disconnected from its electrical power supply source. Following an internal electrical fault in a propulsion motor, it is expected that the motor will be disconnected from its electrical supply source. With the ship operating at or near rated speed following a casualty to the propulsion plant, the ship will coast down to a stop or until the crew takes action to stop the ship. A windmilling permanent magnet motor will generate a large enough internal voltage to continue to support large fault currents. This research will focus on the fault transient and the motor behavior during the time that the propulsion shaft is windmilling. Shorting the motor terminals will be considered as a means of reducing the power input into the fault.