Armature Reaction on Implementation of Embedded Magnetic Encoder in Fractional-Slot Concentrated-Winding Permanent Magnet Machines
Chao Zhang, Yuchen Wang, Hengliang Zhang, Zheng Wu, Jinxin Tao, Wei Hua
Abstract
The linear Hall sensor-based embedded magnetic encoder features promising industrial applications due to the advantages of low cost, space saving, and relatively high precision and reliability. However, the linear hall signals, produced by linear Hall sensors installed at stator slot openings, are influenced by both permanent magnet field (PMF) and armature reaction field (ARF) under on-load condition. Normally, the PMF is used to estimate the rotor angle, whereas the ARF will deteriorate the accuracy of angle estimation. In this article, for double-layer fractional-slot concentrated-winding (FSCW) surface-mounted permanent magnet synchronous machine (SPMSM), a general analytical model of the ARF at slot openings is proposed. The typical topologies with the slot-pole combinations of 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> = <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q<sub>s</sub></i> ± 1 and 2 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> = <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q<sub>s</sub></i> ± 2 are selected for the analytical derivation, where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> is the number of pole pairs and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q<sub>s</sub></i> is the number of stator winding slots. Based on the proposed analytical model, it is innovatively proved that the ARF at some specific positions is almost zero in FSCW-SPMSM, providing a reference for the location of linear Hall sensors where the effect of ARF on linear Hall signals can be ignored and the accuracy of position calculation can be improved theoretically. The results are verified by finite element analysis and experiments on a 12s/10p machine.