Performance evaluation of a vehicle traction drive based on a Permanent Magnet synchronous motor equipped with a mechanical flux weakening device

In permanent-magnet motors used for vehicle traction application a well-known problem is the need to weaken the flux at high speeds. This is generally done by injecting a suitable demagnetizing current along the d axis. An alternative method has been recently proposed by the authors based on an Interior-Permanent-Magnet (IPM) synchronous motor equipped with a mechanical device which activates at high speeds by centrifugal force causing a significant reduction in the permanent magnet flux with no need for injecting d-axis stator currents. The performance of a road vehicle traction drive employing this machine under a maximum-torque-per-ampere control is investigated in this paper assuming a typical driving cycle. It is shown that remarkable benefits can be achieved in terms of energy saving, overload capability enhancement and speed range extension potential.