In-wheel motors bring a fundamental change in electric vehicle technology by removing conventional mechanical components and freeing up space inside the vehicle body. This approach ultimately helps to realize all-wheel independent control for improved vehicle dynamics and increased vehicle design freedom. However, when space allowed for an in-wheel motor is taken into consideration, high torque density, high efficiency, and wide speed range capability are typically required. This paper specifically investigates a 20pole-24slot surface permanent magnet synchronous motor (SPMSM) with consequent pole (CP) rotor for in-wheel direct drive since this topology is well suited for high pole motors and thus high torque direct drive applications. Extensive finite element analysis (FEA) is carried out to characterize the proposed motor and the practical feasibility of the proposed motor is discussed. Finally, the validity of the analysis was experimentally verified.Index Terms-Consequent pole (CP), fractional slot, direct drive, outer rotor, finite element analysis (FEA), surface permanent magnet synchronous motor (SPMSM), in-wheel drive.

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This paper discloses the development of 15-kV class intelligent universal transformer (IUT) to show system level design, circuit topology, and prototype test results. The complete system is split into two stages: (1) high-voltage ac to low-voltage dc and (2) low-voltage dc to low-voltage ac. With the adoption of silicon carbide (SiC) devices, the high-voltage front-end ac to low voltage dc conversion stage achieves 98.4% efficiency, and the complete power stage can be naturally cooled. With the adoption of auxiliary resonant soft-switching inverter, the second stage achieves 99.2% efficiency.Overall the system has been demonstrated at 97.5% efficiency without forced-air cooling. Extended 8-hour testing was conducted to ensure long-term operation reliability. Overall efficiency and voltage regulation were compared with that of a conventional transformer for justification of IUT adoption.

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