Novel Dual Inverter Sub-Harmonic Synchronous Machines

Sub-harmonic synchronous machines (SHSMs) are a relatively new breed of brushless wound field synchronous machines considered alternatives to many electric machines in transportation electrification applications. This article presents two dual inverter SHSMs (DI-SHSMs) having unique two-layer and three-layer stator winding topologies. The two inverters provide the stator windings with two sets of balanced three-phase currents. These two and three-layer windings are arranged in such a way that they can generate both fundamental and sub-harmonic magnetomotive force (MMF). Furthermore, the fundamental MMF component of this machine is four times the sub-harmonic MMF component used for the brushless operation. In contrast, the sub-harmonic MMF is used for field excitation, which leads to brushless operation. Two eight-pole, 48-slot, two-inverter, two-layer, and three-layer sub-harmonic machines are designed to validate the concept through a 2-D finite element analysis (FEA) of these new topologies, showing a better overall torque profile and performance as compared with the other sub-harmonic and brushless wound field synchronous machines.