A Unified Model for Field Weakening Operation of Synchronous AC Machines

Synchronous AC machines, permanent magnet or otherwise, have similar fundamental characteristics but, they are traditionally analyzed using separate models and individual field weakening algorithms. In this work, a unified synchronous machine model is first developed using surface permanent magnet rotor and synchronous reluctance rotor that can have an arbitrary angular offset between the rotors as building blocks. A unified model for field weakening operation is then developed using the unified machine model and validated using finite element analysis. The algorithm developed in this paper can be used to determine the current command trajectory and analyze the field weakening operation characteristics of a wide array of synchronous AC machines, including displaced reluctance axis machines.