Analysis of torque behavior of permanent magnet synchronous motor in field-weakening operation

A variety of efficient control strategies for synchronous motors have been proposed in recent years. Many of them use the rotary or stationary two dimensional axes in order to make the control algorithm easier. However, trying to describe the motor behavior using just two axes is either impossible or at least not complete. Neglecting the real flux density distribution of motors, leads even to wrong or at least naive interpretation about the functionality of the machine. In this paper a new approach for understanding the torque development of a permanent magnet synchronous motor in the field weakening region is developed and verified with experimental results. The description of induced voltage and torque using flux density distribution in the air gap offers a deep insight into the functionality and behavior of a electric machine.