Comparative study of short-pitched and fully-pitched SRMs supplied by sine wave currents

This paper comprehensively investigates 3-phase, 12-slot, and 8-pole switched reluctance machines (SRMs) with different winding configurations, e.g. double/single layer, short/fully pitched. Comparisons in terms of self- and mutual inductances, and on-load torques have been carried out using 2-D finite element method (FEM) for conventional and mutually coupled, double layer winding switched reluctance motors (SRMs) as well as fully-pitched and single layer winding SRMs. The numerical results have shown that the fully pitched switched reluctance machine (FPSRM) has the highest inductance variation against rotor position and hence produces the highest on-load torque if the machine is not heavily saturated. However, its significant longer end-winding will leads to higher copper loss. This can eventually jeopardize its torque vs copper loss performance. To boost torque production while maintaining short end-winding and hence low level of copper loss, two short-pitched, single layer winding SRMs with similar winding configurations to those of conventional and mutual coupled, double layer winding SRMs can be employed. It is found that for the same copper loss and without heavy magnetic saturation, both single and double layer mutually coupled SRMs can produce higher on-load torque compared to their conventional counterparts. Moreover, single layer mutually coupled SRM can achieve comparable torque against copper loss performance to the FPSRM but with much shorter end-winding and also smaller volume.