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 (VF-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 (SLλ^sT) - 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.