Abstract
This paper discusses a magnetization state (MS) manipulation method at high speeds with low vehicle vibration for variable flux permanent magnet synchronous machines (VF-PMSMs). VF-PMSMs can achieve lower driving cycle losses compared to conventional PMSMs by changing the MS in the medium speed and medium torque range. To maximize this advantage for reducing driving cycle losses, the MS manipulation capability in this range, which requires higher voltage to change MS than that required in the low speed range, is critical. However, the capability has not been researched very well. In this paper, a MS manipulating method using a straight line stationary flux linkage trajectory (SLλsT) is investigated and evaluated. This method uses a straight line flux linkage trajectory in the stationary frame so that the DC bus voltage utilization is maximized while the flux linkage achieves the desired magnetizing point without demagnetization. This method was experimentally evaluated with EV-scale VF-PMSMs, and it was found to achieve full magnetization at a speed almost two times higher than the base speed. The effect of this method on vehicle vibration was studied via simulation using the experimental result and a simple vehicle model that emulates a vehicle powertrain for traction applications.
