Permanent-Magnet Synchronous Machine model for urban transport applications

Permanent-Magnet Synchronous Machines (PMSM) become more and more interesting for urban transport applications (tramways and busses with electric drives), because performance increases at decreasing cost. Their compact design facilitates customer-friendly low-floor design and reduces weight, the efficiency at rated power can be by about 3 percent higher. Demands concerning ruggedness can be fulfilled by interior permanent-magnet (IPMSM) design. Sufficient field-weakening capability by negative d-stator current component allows for a suitable speed range with constant power and for emergency braking. Adequate real-time control systems with high torque dynamics require suitable models of the machine. A high level of complexity, like in finite-element models, cannot be used because of limited calculation time. If the model is too simple, important effects are neglected, for example the reluctance torque of IPMSM. The model should also give the main parameters for the operation of the machine and allow the rating of the converter feeding the machine. With special respect to field weakening and reluctance torque, optimal operation points have to be identified, taking into account the limited rating of the converter. For this, special conditions of light-rail applications like emergency braking are considered. In this way the machine can be operated with high efficiency at minimal losses of machine and converter and fulfill the demanding conditions of urban transport applications. This paper gives a suitable model for the IPMSM fulfilling the above requirements and suggests suitable areas of operation based on an example machine.