Induction machine performance with fractional-slot concentrated windings
Purpose - The purpose of the paper is to investigate the performance of induction machines with fractional-slot concentrated-windings. Design/methodology/approach - This paper examines induction machine performance with fractional-slot concentrated windings using the standard distributed lap windings as reference. Four designs are compared and various performance tradeoffs highlighted. The first machine has integral-slot distributed 2 slots/pole/phase lap winding and it serves as the reference winding. The second machine has a double-layer 1/2 slot/pole/phase winding, a workhorse for brushless DC machines. The third machine has double-layer 2/5 slot/pole/phase winding. Lastly, the fourth machine has single-layer 2/5 slot/pole/phase windings. The comparison includes torque-speed curves (including the effects of major space harmonic components), rotor bar losses, and ripple torque levels. Findings - Based on the analysis results presented here, the traditional distributed lap winding is proven to be superior to FSCW in terms Of torque production and rotor bar losses for induction machine applications. The 1/2 spp shows some promising results in terms of torque production, in addition to significant reduction and simplification of end turns with lower number of coils albeit with more turns/coil (12 slots vs 48 slots). The penalty is the additional rotor bar losses due to the 2nd and 4th harmonic mmf components. The 2/5 spp is not promising for torque production and should be avoided. The transient simulation results that simultaneously take into account the effects of all space harmonics and magnetic saturation showed comparable trends compared to the harmonic analysis results. It has also been shown that FSCW tend to have higher torque ripple compared to distributed windings. Originality/value - To the best of the authors' knowledge, this paper for the first time attempts to quantitatively address the tradeoffs involved in using FSCW in induction machines.
induction machines performance fractional-slot concentrated windings distributed comparison