Application of Halbach magnetic assembly in the outer rotor of BLDC motor to improve its performance

Abstract

Modern electric vehicle drive systems are steadily moving toward simplified kinematics and improved energy efficiency. One promising solution is the use of hub motors, in which the electric motor is integrated directly into the vehicle wheel. Using external rotor motors as wheel hub motors is a technically sound and, in some cases, highly effective solution, especially for low- and medium-power electric vehicles. However, its effectiveness depends on a number of factors: design, operating mode, operating conditions, and drive system requirements. This article discusses the design of an external rotor BLDC using a Halbach magnet assembly, which will address the challenge of producing a highly efficient motor for vehicle hub motors. The motor was studied with various ratios of the outer rotor magnet sizes with radial and tangential magnetization vectors, and the optimal option for achieving the best motor performance was determined. It was demonstrated that for the 1000W motor under study, magnet mass can be reduced by 27% compared to a conventional motor. The magnetic field is concentrated in the working air gap, resulting in a 29% reduction in magnetic flux density in the rotor ring, which helps reduce magnetic losses and attenuate field leakage outside the magnetic circuit. The use of the Halbach magnetic system improves the motor’s energy and performance characteristics: efficiency increases from 87.6% to 89.7%, and overload capacity increases by 6.4%, demonstrating increased energy conversion efficiency and improved dynamic performance of the electric machine.