Improving Efficiency of a Pole-Changing Vernier Machine Considering Residual Magnetic Flux Density

Sung-Hyun Lee, Jung-Woo Kwon and Byung-Il Kwon ()
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Sung-Hyun Lee: Department of Electrical and Electronic Engineering, Hanyang University, Ansan 15588, Republic of Korea
Jung-Woo Kwon: Department of Electrical and Electronic Engineering, Hanyang University, Ansan 15588, Republic of Korea
Byung-Il Kwon: Department of Electrical and Electronic Engineering, Hanyang University, Ansan 15588, Republic of Korea

Energies, 2023, vol. 16, issue 18, 1-12

Abstract: This paper presents the efficiency improvement of a pole-changing vernier machine (PCVM) by considering the residual magnetic flux density ( B r ) of low coercivity force (LCF) permanent magnets (PMs). The PCVM operates in two modes: vernier machine (VM) mode and permanent magnet synchronous machine (PMSM) mode, achieved through pole-changing. Pole-changing involves reversing the magnetic flux direction of LCF PM to alter the number of rotor pole pairs. By changing the number of rotor pole pairs, the PCVM operates as a VM mode at low speeds, providing high torque, and as a PMSM mode at high speeds, offering high efficiency. To achieve this, a combination of high coercivity force (HCF) PM and LCF PM is utilized in a single structure. The magnetic flux direction in the LCF PM is determined by B r , and the highest efficiency is achieved when B r reaches its maximum value | B r m |. This paper focuses on improving efficiency by obtaining B r m in VM mode and − B r m in PMSM mode through the design process. Additionally, finite element analysis (FEA) is employed to compare the performance of the improved model, which considers B r , with that of the conventional model, designed without considering B r . The improved model achieves higher B r values in each mode compared to the conventional model, resulting in increased torque density. Consequently, this leads to improved efficiency.

Keywords: efficiency improvement; pole-changing; residual magnetic flux density; vernier machine; permanent magnet synchronous machine (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
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