Analysis of Magnetizing Trajectories for Variable Flux PM Synchronous Machines Considering Voltage, High-Speed Capability, Torque Ripple, and Time Duration

This paper discusses various transient trajectories for increasing the magnetization state (MS) of variable flux permanent magnet synchronous machines (PMSMs), a class of PMSM where the magnets are demagnetized and remagnetized using the drive inverter during drive cycle operation. To manipulate MS, a magnetizing current pulse can be used, which may drive a large amount of flux linkage in the machine. As a result, above low-speed operation, a large voltage may be required from the inverter. This paper extends several existing methods for improved voltage properties, and proposes and experimentally evaluates a new method-a straight line stationary frame flux linkage trajectory-for higher speed capability. The presented trajectories, along with existing trajectories, are organized into families and compared regarding their required voltage, high-speed capability, torque ripple, and time duration.