Optimal rotor design for reducing the partial demagnetization effect and cogging torque in spoke type PM motor

Abstract

Articles you may be interested inEffect of rotor eccentricity on electric parameters in a PM brushless motor with parallel winding connections J. Appl. Phys. 105, 07F121 (2009); 10.1063/1.3076420The torque ripple reduction of a concentrated winding synchronous reluctance motor according to stator and rotor structure variations using response surface methodology J. Appl. Phys. 103, 07F133 (2008); 10.1063/1.2839348Effect of skewing the rotor teeth on the performance of doubly salient permanent magnet motors A comparative analysis of permanent magnet-type bearingless synchronous motors for fully magnetically levitated rotors This paper proposes an optimized rotor pole shape that can effectively reduce the partial demagnetization effect and cogging torque. First, for reducing the peak amplitude of the external field that directly affects the partial demagnetization on the permanent magnets in spoke-type permanent magnet motor, we conduct a variation of core shape and insertion of a barrier. Second, with the rotor shape obtained by the first processes for reducing the partial demagnetization effect, another part of the rotor pole is varied to make better sinusoidal distributed air gap flux density to reduce the cogging torque. In the process of designing the rotor pole shape, a steepest descent method and a response surface method are applied for improving convergence. By using the finite element method, we show that the optimized rotor pole shape drastically reduces the effect of the partial demagnetization and cogging torque.

Local demagnetisation analysis of a permanent magnet motor

“…2b shows that the value of the permeance coefficient is constant as the PM temperature increases. An operating point is formed below the knee point because of the change in the B-H curve [5,6,8,12]. Fig.…”

“…Fig. 2c shows that when the temperature and permeance coefficient are constant, the parallel permeance line shifts to the left if inverse magnetic flux is applied to the PM [5,6,8,9].…”

“…However, the problem is that irreversible demagnetisation of the PM could occur as the temperature rises. Irreversible demagnetisation permanently changes the characteristic of the PM [5][6][7][8][9] and renders it inappropriate for usage. When the grade of a PM is known, the occurrence of irreversible demagnetisation is determined by its thickness, the air-gap length and the magnitude of the field distributions because of the stator currents.…”

“…However, even if these parameters are designed to be robust against demagnetisation, irreversible demagnetisation can still occur at a local point in the magnet. Studies have been carried out to compensate for local irreversible demagnetisation according to rotor type and position [5,[7][8][9][10][11]. Studies on irreversible demagnetisation caused by the shape of the PM have also been conducted [6,9].…”

Analytical analysis and implementation of a low-speed high-torque permanent magnet vernier in-wheel motor for electric vehicle

“…By applying the boundary conditions and the radial magnetization function, the airgap flux density can be deduced. 5,6 The modulation effect of the FMPs can be described by using the concept of complex relative airgap permeance. The permeance parameters are calculated by using the Schwarz-Christoffel transformation in such a way that the slotted structure can be transformed from the original plane to a new plane in which the structure becomes smooth.…”