A Computationally Efficient PM Power Loss Mapping for Brushless AC PM Machines With Surface-Mounted PM Rotor Construction

Abstract

--This paper describes a computationally efficient approach for mapping the rotor power loss in permanent magnet (PM) machines. The PM loss mapping methodology discussed here utilises a small number of time-step finite element analyses (FEA) to determine the parameters of a functional representation of the loss variation with speed (frequency) and stator current, and is intended for a rapid evaluation of machine performance over entire torque-speed envelope. The research focus is placed on field-oriented controlled brushless AC PM machines with surface-mounted PM rotor construction, although the method could be adapted for other rotor formats. The loss mapping procedure accounts for the axial-segmentation of PM array through the use of an equivalent electrical resistivity of the segmented PM array, obtained from 3D FEA. The PM loss can be accurately mapped across the full operational envelope, including the field weakened mode, through a single three-dimensional (3D) and four two-dimensional (2D) time-step FEAs. The proposed methodology is validated on an 18 slots, 16 poles surfacemounted brushless AC PM machine design. The loss mapping procedure results agree closely with the computationally demanding alternative of direct 3D FE prediction of the PM power loss undertaken at each of the machine's operating points.Index Terms-PM power loss, surface-mounted brushless AC PM machines, computationally efficient methodology, loss mapping, finite element analysis (FEA), segmented PM array. I. INTRODUCTIONHE accurate prediction of loss and its variation with load is an important element in the design of electrical machines [1]. Vehicle propulsion applications are particularly demanding as the understanding of machine efficiency over the entire working envelope and under specific control and operating conditions is usually required [2]- [4]. Typically an electric propulsion motor operates under constant torque and field-weakened control regimes. Further the motor input voltage at a given operating point can be highly variable, depending on the battery state of charge. The loss derivation, in such cases, is a time demanding and computationally intensive process requiring numerous analyses to predict each component of loss over the full range of operation.In general, the sources of loss present within an electric machine can be categorised as mechanical and electromagnetic. Mechanical loss is attributed to the frictional effects within the bearing assembly (bearing loss) and fluid dynamics or aerodynamics effects within the motor body (windage or drag loss) [5]. Electromagnetic losses are usually associated with active parts of the motor assembly and include the iron, winding and permanent magnet (PM) loss components [6]- [8].Recently, there has been increased interest in methods for accurate and computationally efficient derivation of the electromagnetic loss components [1], [9], [10], that can be easily incorporated within design software tools. Of particular interest is the automated generation of loss/efficien...

High-Speed Electric Drives: A Step Towards System Design

“…The accurate evaluation of the eddy-current losses in the permanent magnets and the retaining sleeve require a 3D FEA with a remarkable fine mesh in the regions where the eddy current arise. Fully analytical and mixed FE-analytical methods have been proposed in the literature to avoid such high computational expensive simulation [33], [34]. In the following, the approach proposed in [35] has been adopted to calculate the eddy current losses in the solid parts of the rotor.…”

Fast calculation of eddy current losses caused by pulse‐width modulation in magnets of surface‐mounted PM machines based on small‐signal time‐harmonic finite element analysis

“…Besides, the calculation of PM ECL with the TSFEA under the SCS supply is faster than that under the PWM VSI supply. For further improving the calculation speed of the PM ECL under SCS supply, the numerical method in [23] or other analytical methods [16] can be applied, which, however, is not within the scope of this paper.…”

Permanent-Magnet Eddy-Current Losses: A Global Revision of Calculation and Analysis

“…This method incorporated the 3D end-effects. The algorithm for mapping eddy-current loss within surface-mounted PMSM over a wide range of operating conditions was presented in [123,124]. The method required four FEA simulations for open-circuit at rated speed (n R ), at particular reference speed (n w ) in the field weakening region, rated current in the quadrature axis (I q ), rated current in the direct axis (I d ), and reduced current in the d-axis.…”