Synchronous Motor Railcar Propulsion

Development of ac motor drives for rail transit car has centered on the induction motor with pulsewidth modulated (PWM) inverter control. Interest in the induction motor as a replace for the series dc traction motor stems from the simplicity of the squirrel cage rotor of the induction motor. In this article, the short-comings of PWM inverter-induction motor transit car drive are examined. It is shown that the synchronous, or brushless dc, motor drive can provide performance exceeding both the PWM inverter-induction motor and the conventional dc motor in the transit car application.