Influence of MMF Space Harmonic on PM Eddy- Current Losses in a Modular Fault-Tolerant In-Wheel Motor under Open-Circuit Faulty Operations

This paper investigates the influence of magneto motive force (MMF) space harmonic on permanent magnet (PM) eddy-current losses in a modular fault-tolerant in-wheel motor under open-circuit faulty operations. First, reconfiguring maximum round MMF with constant amplitude of current is taken as the fault-tolerant (FT) strategy for the open-circuit of one phase in one module. Second, the harmonic components of MMF under the faults and corresponding FT control are analyzed respectively. Then, an analytical model based on multi-loop method for calculating PM eddy-current losses induced by MMF harmonics is proposed. The PM losses induced by each MMF harmonic can be obtained through the model. The total PM losses named Ppm consist of
$P_{mmf}$
and
$P_{slot}$
. The former is induced by spatial harmonics of MMF.
$P_{slot}$
, the most important losses in PMs, are those generated by the fundamental frequency magnetic flux due to the stator slot openings. The influences of
$P_{mmf}$
and
$P_{slot}$
on the total PM losses under various operations are analyzed respectively. Finally, the analytical results are verified through finite element method (FEM).