Novel Field Weakening Technique for Surface Mounted Permanent Magnet Machine using Current Regulated Voltage Source Inverters

Field weakening control is a key technique for high speed operation of electrical machines. A novel Current Regulated Voltage Source Inverter (CRVSI) operation strategy is adopted in this paper to achieve high speed operation from Surface Mounted Permanent Magnet Synchronous Motor (SMPMSM). This strategy avoids any kind of previously proposed winding switching and achieves same benefits of high flux weakening. Machine operation is divided into two modes: two 3-phase CRVSI operation and three single phase CRVSI operation. During first mode of operation machine can be operated at maximum torque conditions as well as d-axes current control is applied for first stage of flux weakening. In second mode of operation, when machine reaches its constant power operation limit, CRVSIs operation is modified. Three 1-phase CRVSI are established such that machine operation reverts to achieve unity internal power factor at the elevated speed. Again d-axes current control is adopted to achieve second stage of flux weakening. Suitability of suggested current flow paths for the proposed topology is supported by inductance variation calculations. Furthermore effect of slot per pole per phase configuration on this flux weakling topology is discussed. Also constant power capability of the machine is examined for high speed operation. Initial experimental results are provided to validate the simulation results.