Assessment of Control Strategies for Synchronous Reluctance Motors

This paper discusses the different control strategies adopted to optimize the operation of the synchronous reluctance motor and how these techniques apply for an actual prototype. At first, based on the Park model of the machine, the most popular optimization techniques are recalled in terms of current control requirements, such as maximum torque/current, maximum power factor, and maximum torque/flux. A speed vector control scheme is presented, able to implement such techniques by taking account the physical limits of the feeding voltage and current. The further criterion of maximum efficiency is also considered, not evaluable in terms of analytical relations. Due to the non linearity of the magnetic circuit, cross-coupling effects and iron losses, the optimizing control trajectories are evaluated by means of a numerical Finite Elements model analysis and validated by experiments. The study is applied to a prototype of synchronous reluctance motor with flux barriers rotor, designed to have the same stator core of a commercial three-phase 3kW induction motor. The results outline the performance of such machine, able to compete with permanent magnet or induction motors in inverter driven application.