Principle of Variable Leakage Flux IPMSM Using Arc-Shaped Magnet Considering Variable Motor Parameter Characteristics Depending on Load Current

This paper presents a novel methodology investigating a characteristics of variable leakage flux interior permanent magnet synchronous machine (VLF-IPM) using arc-shaped magnets. In general, motor parameters such as magnet flux, psi(a), inductances on d-q axes, Ld and Lq, are dealt as constant values, while motor parameters need to be dealt as variables depending on load currents for VLF-IPM machines. In this paper, the psi(a) was calculated as a function of d-q axis currents, i(d) and i(q), by using magnet flux linkages, lambda(d) and lambda(q), calculated by FEA. By plotting operating point trajectories on the psi(a) map so as to trace the torque-speed envelope, it was unveiled that motor parameters of the VLF-IPM suitably vary accordance with operating conditions. On the other hand, a spatial MMF distribution was also evaluated in order to clarify an effect of the arc-shaped magnets in terms of iron loss reduction, then it was shown by FEA and experiment that the VLF-IPM can have a wide high efficiency range by both variable leakage flux property and low iron loss property. In addition, an effect on current control by motor parameters variation was also evaluated, then it was found that the VLF-IPM with arc-shaped magnet achieves both suitable variable characteristics and high efficiency property without any control issues.