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Abstract: The implementation of concentrated windings in interior permanent magnet (IPM) machines has numerous advantages over distributed windings, with a major disadvantage being the decrease in saliency ratio. Theoretically, this would result in a lower field weakening range which is undesirable for traction applications. Although it is revealed in some studies that concentrated winding results in lower saliency ratio, experimental techniques used for accurately acquiring the saliency ratio of IPM machines with concentrated windings are yet to be fully understood. This study presents a proposed finite-element (FE) method, which is derived from the experimental AC standstill test method. With this method, the d- and q-axis inductances (L^sub d^ and L^sub q^) of the IPM machine with fractional-slot concentrated windings can be accurately determined. Limitations of this method are discussed. Subsequently, this method is used to determine L^sub d^ and L^sub q^ of various winding configurations and rotor designs. From repeated FE testing using Flux2D, the authors derive a set of general rules for optimising the saliency of an IPM machine with fractional-slot, single-layer concentrated winding.
(ProQuest: ... denotes formulae omitted.)
1 Introduction
The interior permanent magnet (IPM) machine is an appropriate choice for traction applications because of its high power density, high efficiency and high field-weakening capability. The application of concentrated winding in machines to improve its field-weakening performance further has been of recent interest, especially for the surface permanent magnet (SPM) machines [1-3]. El-Refaie and Jahns proved in [1] that the application of concentrated winding in SPM machines causes more than a six-fold increase in Ld for a 2/7 slots per pole per phase (Spp) machine, hence reducing the characteristic current and significantly improving the condition for optimal flux weakening. El-Refaie et al. also proved that a 5:1 wide constant power speed range was achievable for the 2/5 <Spp SPM with concentrated windings in [4],
Unlike the SPM machine, the IPM machine is subjected to not only one, but two conditions which determines the field weakening performance of the machine: the characteristic current (If) given by (1) and saliency ratio (ξ) given by (2)
... (1)
where
I^sub x^ characteristic current (A)
[straight phi]^sub m^ magnet flux linkage (Wb)
L^sub d^ P-axis inductance (H)
... (2)
where
ξ saliency ratio
L^sub q^...