Optimal Design of High-Speed Electric Machines for Electric Vehicles: A Case Study of 100 kW V-Shaped Interior PMSM

Abstract

The need of compact machines increased in recent years due to increases in raw materials’ price. Hence, many studies are currently being conducted on high-speed challenges to propose an optimal design methodology. AC losses in windings are often not included in the optimization process and are treated in post-processing by choosing a suitable conductor’s diameter to mitigate skin and proximity effects. This paper presents an optimization and design methodology for high-speed electric machines considering these losses, using models with an interesting trade-off between computation time and accuracy, which is helpful for large-scale optimization, in which more than 9,600,000 machines are evaluated. Optimizations are conducted on 100 kW high-speed one-layer V-shaped interior permanent magnet synchronous machines, widely used in vehicles thanks to their high power density, based on the specifications of the Peugeot e208, for different values of pole pairs and maximum speed. The influence of lamination thickness, fill factor, and maximum current density on the optimal design is also investigated. This paper concludes the utility of increasing speed to achieve high power density and proposes best alternatives regarding automotive constraints. Results show that the number of pole pairs is not always a key parameter in obtaining the lowest volume, especially at high speed.

AC Losses in Windings: Review and Comparison of Models With Application in Electric Machines

“…This model is valid only when the slot is entirely and uniformly filled with conductors. Conditions concerning equivalence between DFEA and SFEA are given in [32].…”

“…To reduce computation time, an improved hybrid model was proposed [31] using a simple FEA model and considering 2D magnetic field with arbitrary waveform. Reference [32] proposes a new design and optimization methodology including proximity effect losses in the optimization process using simple FEA model. For losses due to circulating currents, a hybrid model [33] was developed using the induced voltage in each strand and applied to an interior permanent magnet synchronous machine (IPMSM).…”

“…of electric machines' windings used for in several electric and hybrid vehicles[32], [48],[49],[50].…”

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“…The inevitable necessity of efficient eco-friendly products and machinery has paid the way for the development of electric vehicles. Various electric vehicle technologies are compared and suggested that the hybrid electric vehicle (HEV) is the most suitable one in terms of efficiency of operation, and reduced emission [1]. Also, due to the low availability of fossil fuel resources, the electrified vehicle has gained more importance [2][3].…”

“…Different types of electric motors are used for HEVs, and they are listed in [3]. Generally, DC motors are less preferred because of the periodic maintenance of brushes and commutator segments [1]. Induction motors are used in Tesla cars due to their wide range of speed control, easy manufacturing, maintenance, and low cost, but they suffer from low power density, hence they are less preferred compared to synchronous motors [7][8][9][10].…”