Electromagnetic Characteristics of Dual-Air-Gap Surface Permanent Magnet Synchronous Motor

Abstract

This paper introduces a novel dual-air-gap surface permanent magnet synchronous motor (DAG-SPMSM) and investigates its electromagnetic characteristics. The motor comprises two stators (inner and outer) and a single rotor with permanent magnets on both sides (inner and outer). The magnets are arranged in a zig-zag configuration to isolate the inner and outer stator and rotor magnets. Additionally, a magnetic shield is incorporated into the rotor to further isolate the rotor magnetic flux, which results in a localized short flux path that can reduce core loss. The insertion of the magnetic shield also affects the flux path, reducing torque ripple. The electromagnetic characteristics, such as flux path, flux density, and torque, are analyzed using finite element analysis. The effectiveness of using a magnetic screen is also evaluated, and simple experiments are conducted to validate the observed characteristics of the proposed motor.

Magnetic Screen Effects on Torque Ripple and Efficiency of Dual Air-Gap Surface Permanent Magnet Synchronous Motor

“…The windings for the outer and inner motors are connected in series for each corresponding phase. The PM arrangement has been explained in [29], with the red and blue colors indicating north and south polarity, respectively. As shown in the figure, the proposed design allows the motor to be effectively separated into two distinct parts, namely the outer and inner motors.…”

“…As shown in the figure, the proposed design allows the motor to be effectively separated into two distinct parts, namely the outer and inner motors. This separation is facilitated by the placement of the magnetic screen in the middle of the rotor and the PM arrangement, as previously described in [29]. As a result, there is no mutual flux between the outer and inner motors, and the flux becomes localized with a much shorter path.…”

“…In this paper, we propose a DAG-SPMSM. The construction of the motor was previously explained in the authors' earlier work [29]. This radial-type motor features two stator cores and one rotor core in the middle.…”

“…This radial-type motor features two stator cores and one rotor core in the middle. At the center of the rotor, a magnetic screen is positioned with the primary purpose of completely isolating the outer and inner motors, as previously elucidated in [29]. However, the design of the magnetic screen was not discussed in the previous study, as its size was chosen arbitrarily based on the flux density distribution in the rotor.…”

“…This paper is organized as follows. First, the motor's structure, which has been explained in [29], is summarized in Section 2 for the readers' convenience. Section 3 presents the simulation results obtained by varying the magnetic screen size as a percentage of the overall rotor thickness.…”