Analytical Model of Torque-Prediction for a Novel Hybrid Rotor Permanent Magnet Machines

Abstract

This paper presents an analytical method for predicting the electromagnetic performance in permanent magnet (PM) machine with the spoke-type rotor (STR) and a proposed hybrid rotor structure (HRS), respectively. The key of this method is to combine magnetic field analysis model (MFAM) with the magnetic equivalent circuit model. The influence of the irregular PM shape is considered by the segmentation calculation. To obtain the boundary condition in the MFAM, respectively, two equivalent methods on the rotor side are proposed. In the STR, the average flux density of the rotor core outer-surface is calculated to solve the Laplace's equation with considering for the rotor core outer-surface eccentric. In the HRS, based on the Thevenin's theorem, the equivalent parameters of PM remanence B reB and thickness h pme are obtained as a given condition, which can be utilized to compute the air-gap flux density by conventional classic magnetic field analysis model of surface-mounted PMs with air-gap region. Finally, the proposed analytical models are verified by the finite element analysis (FEA) with comparisons of the air-gap flux density, flux linkage, back-EMF and electromagnetic torque, respectively. Furthermore, the performance that the machine with the proposed hybrid structure rotor can improve the torque density as explained. INDEX TERMS Analytical method, hybrid PM rotor structure, rotor core outer-surface eccentric, magnetic equivalent circuit model (MECM).

Analytical Model of Air-Gap Field in Hybrid Excitation and Interior Permanent Magnet Machine for Electric Logistics Vehicles

“…Content may change prior to final publication. Define A si as the effective magnetic flux area corresponding to the ith magnetic potential source, so, when ψ represents the angle with reference to d axis, the flux density of outer side of the rotor and the Fourier expansion on the calculated position can be expressed as [40]: (28) where r and α are the position of the calculated point, representing the radial length and the circumferential angle, respectively. The general solution of (28) in different regions can be expressed by separation of variables method as follows: (31) where i, ii, and iii represent the regions of the slot, slotopening, and air-gap.…”

“…where φ is equal to 2πα p1 . According to (40), the partial derivative of the radius of the pole shoe surface is calculated by:…”

“…However, many scholars adopted the hybrid analysis method combining EMC and Maxwell's equations in the spoke-type magnets motor. To obtain the boundary condition on the rotor side, different models are presented considering the irregular PMs shape, teeth saturation, and the nonlinearity of magnetic materials, respectively [40]- [42].…”

Electromagnetic Performance of the Novel Hybrid-Pole Permanent Magnet Machines for High Peak Torque Density

“…The key parameter of the BHRPM rotor is the thickness of surface-mount PM and spoke type PM [5]. In fact, the spoke type is designed as shown in Fig.…”

“…The high peak torque density is important electromagnetic indicator which is closely related to the overload capability due to the high dynamic response with a short-time operation. In actual, a low inertia torque is expected by reducing the moment of inertia as small as possible in the rotor outer diameter [5].…”