Flux weakening of surface permanent-magnet machines in over-torque operation mode

This work deals with flux weakening operation mode of surface permanent-magnet machines. Traditionally, the flux-weakening operation mode has been used to achieve speeds beyond the rated speed with the rated voltage. The same principle can be applied to reach torques higher than the rated one. In this work flux weakening in over-torque operation mode is explained. The stator resistance influence is studied and the theory is applied in a numerical example.