Behavior Study of Permanent Magnet Synchronous Machines Based on a New Normalized Model

Permanent magnet synchronous machines (PMSMs) are widely used in many applications. The performance of the PMSM is highly dependent on the motor parameters. Many research studies have been done to evaluate the PMSM performances in terms of maximum torque capability, power capability, and field-weakening capability. This paper proposes a new normalized PMSM model and uses two parameters, characteristic current and saliency ratio, to uniquely define the motor characteristic. Based on this normalized model, the full map motor behaviors, including torque capability, power capability, torque/power-speed characteristics, and power factor behaviors, are studied parametrically. A new unitless metric, i.e., copper loss factor, is introduced to evaluate the copper loss variation of PMSMs. The saturation effect on the motor behavior is studied based on the 2004 Prius traction motor, which confirms that the field-weakening characteristic can be well predicted using the linearized model. A new design flow for traction PMSMs, which requires wide-speed operation, is proposed based on the full map motor behavior study, and a prototype machine is designed accordingly. The behavior study and the effectiveness of the traction motor design flow are validated experimentally by the prototype.