Performance Analysis of Concentrated Wound-Rotor Resolver for Its Applications in High Pole Number Permanent Magnet Motors

High pole number permanent magnet (PM) motors, due to their high torque density, have been receiving considerable attentions in recent years. To achieve an accurate position control in PM machines, resolvers are suggested for industrial applications. Mechanical and electromagnetic considerations in the case of high pole number resolvers lead the machine designers to choose small cores with low slot numbers. This paper proposes two different on-tooth winding configurations to achieve high pole number without increasing the slot numbers, while the accuracy of the detected position is intended to be the maximum value. Variable turn on tooth winding (VTTW) is compared with fractional slot concentrated winding (FSCW) for two-phase machines. By the aid of winding function's harmonic contents and winding factors, the accuracy of different configurations is analyzed and confirmed by the 3-D time stepping finite-element method. Results show that the wound field resolver equipped with FSCW has higher accuracy than the VTTW. Moreover, it is shown that concentrated winding suffers from sub-harmonics. In this regard, a modification on the rotor winding is performed to decrease the total harmonic distortion of output signals and decrease the estimated position error. In addition, the role of winding layers and displacement angle between them is further investigated in this paper. Finally, a prototype with 20-pole 6-layer FSCW resolver has been constructed. Practical results are in good agreement with the analytical predictions.