Theoretical limitations to the field-weakening performance of the five classes of brushless synchronous AC motor drive

A new parameter plane approach graphically illustrates the effect of the drive parameters on the shape of the optimal field-weakening characteristic of brushless synchronous AC motor drives with a limited inverter kVA rating. It unifies previous approaches to this problem and allows fundamental performance limitations of these drives to be identified. Contour plots of important characteristics such as power at base speed and constant power speed range are illustrated in the parameter plane. These characteristics are calculated using a circle diagram approach to obtain the optimal torque control strategy for each of the five main classes of brushless synchronous AC motor drive