Yunkai Huang

Thermal Analysis of High-Speed SMC Motor Based on Thermal Network and 3-D FEA With Rotational Core Loss Included

This paper presents the thermal analysis of a high-speed motor with soft magnetic composite (SMC). Due to the high operation frequency, the core loss is much greater than the other losses and, hence, is the major heat source in the high-speed motor. Therefore, it is of crucial importance to be able to calculate the core loss accurately. In this paper, the rotational core-loss model is employed and implemented by using 3-D magnetic-field analysis (FEA). Two methods to model the thermal behavior are presented. The first method uses a combination of lumped and distributed thermal parameters, which are obtained from motor dimensions and thermal constants. The second method employs 3-D FEA to accurately calculate the temperature distribution. Core losses are directly coupled into the thermal calculation by keeping the same hexahedral meshing for magnetic-field analysis and thermal analysis. A testing bench for the high-speed SMC motor prototype has been set up to measure the core loss. The temperature rises were measured by thermal probes. The calculation and measurement results are compared and discussed.

Core Loss Modeling for Permanent-Magnet Motor Based on Flux Variation Locus and Finite-Element Method

Core-loss prediction is an important issue in design and analysis of permanent-magnet (PM) motors. Because of the diverse structure, flux distribution, and rotational variation of flux, it is difficult to predict the core loss in a machine exactly. In this paper, a core-loss model for the PM motor is introduced in which flux variation loci in different parts of the motor are predicted by carrying out a finite-element transient analysis. Since the flux variation pattern is complicated, an improved equation based on the conventional three-term expression is used for core-loss calculation. The core-loss model is developed totally in ANSYS parametric design language as a parametric model and it can be used easily for different types of PM motors. Calculation and experiments on a high-speed PM motor have shown that the model can produce results that agree with the experimental ones.

Design and Analysis of a High-Speed Claw Pole Motor With Soft Magnetic Composite Core

Soft magnetic composite (SMC) material is formed by surface-insulated iron powder particles, generating unique properties like magnetic and thermal isotropy, and very low eddy currents. This paper presents the design and analysis of a high-speed claw pole motor with an SMC stator core for reducing core losses and cost. The analyses of magnetic and thermal fields are conducted based on a comprehensive understanding of the property of SMC materials. The 3-D finite-element analysis (FEA) is performed for accurate parameter calculation, design optimization, and thermal calculation. Because of the importance of core loss in high-speed motors, rotational core loss model is employed, and the core losses are coupled directly into thermal calculation by keeping the same hexahedral mesh structure between magnetic field analysis and thermal analysis. Since the rotor modal analysis is very important to high-speed motors, the natural frequencies and mode of the rotor are studied

Analytical Magnetic Field Analysis and Prediction of Cogging Force and Torque of a Linear and Rotary Permanent Magnet Actuator

This paper presents a method for analytically analyzing the magnetic field and predicting the cogging force and torque of a linear and rotary permanent magnet actuator (LRPMA). The tubular mover of the LRPMA is transferred into a planar one by using a proposed magnetic field curvature factor and a relative permeance function for the stator slotting so as to simplify the magnetic field calculation. Magnetic field distributions of the LRPMA when the stator slotting is neglected are analytically analyzed using the magnetic scalar potential, and validated by 3-D finite-element method. The linear cogging force and rotary cogging torque of slotted LRPMA are subsequently predicted by the Maxwell stress tensor method and verified by the experimental results on the prototype.

Analysis of a Novel Switched-Flux Memory Motor Employing a Time-Divisional Magnetization Strategy

This paper presents a novel switched-flux memory motor (SFMM) by artfully incorporating the flux-mnemonic concept into the conventional switched-flux permanent magnet machine. The magnetic susceptibility of AlNiCo PM provides the flexible online controllability of air-gap flux by imposing a transient current pulse. To uniformize magnetization levels of PMs, a time-divisional magnetization strategy (TDMS) is proposed. Due to the uniqueness of hysteresis nonlinearity and instability regarding AlNiCo PM operating point, the time-stepping finite element method (TSFEM) dynamically coupled with a nonlinearity-involved parallelogram hysteresis model (NIPHM) of AlNiCo PM is performed to investigate the electromagnetic performance of the proposed SFMM. The results derived from the combinative algorithm verifies the flux-adjustable capability of the proposed motor equipped with TDMS and the validity of the proposed NIPHM.

3-D Analytical Modeling of No-Load Magnetic Field of Ironless Axial Flux Permanent Magnet Machine

A three-dimensional analytical modeling of the magnetic field of the stator-ironless axial flux permanent magnet (AFPM) machine under open-circuit condition is presented in this paper. It involves the analytical solution of the governing field equations in the region between back-irons in the cylindrical coordinate, in which the magnets are assumed to be axially magnetized and have constant relative recoil permeability. The proposed modeling method is applied to a specific AFPM machine, and the analytical results are in good agreement with those of three-dimensional finite element analysis (FEA).

A General Analytical Model of Permanent Magnet Eddy Current Couplings

An improved practical two-dimensional model for the analytical calculation of the magnetic field distributions in permanent magnet (PM) eddy current couplings is presented to obtain the torque characteristics. By establishing the Cartesian coordinate reference system on the rotating conductor, the PM region is treated as a source of traveling wave magnetic field and then the multi-layer boundary value problem is solved. The formulation for the magnet blocks, the eddy current and saturation effects in the solid secondary back iron, and the equivalence relationships between typical PM shapes, are all reasonably taken into account. Calculation results produced by the proposed analytical model are compared with those from the nonlinear finite element method and experimental measurement.

Thermal Optimization of a High-Speed Permanent Magnet Motor

This paper investigates the losses of a high-speed permanent magnet motor. The iron losses are calculated by a model that can consider the skin effect and rotational loss. The rotor eddy current losses are estimated by a fast hybrid method that can consider the end effect. Pulse-width modulation (PWM) harmonics brought by the voltage source inverter (VSI) are considered in the loss calculations. Then the temperature distribution of the motor is evaluated by using the calculated loss results and computational fluid dynamic (CFD) modeling. Finally, based on the CFD results, the motor structure is optimized to achieve better rotor cooling. The outer slots are closed to force the cooling air flow through the rotor surface. Calculated temperature distributions and optimization results are verified by measurements.

Flux-Regulatable Characteristics Analysis of a Novel Switched-Flux Surface-Mounted PM Memory Machine

A novel switched-flux (SF) surface-mounted permanent magnet (PM) memory machine is proposed by incorporating the flux-memorizable concept into the SF structure. It employs a temporary current pulse to magnetize/demagnetize the aluminum-nickel-cobalt (Al-Ni-Co) PMs so that the air-gap flux can be regulated online for extending its high-speed constant-power region. An analytical hysteresis modeling method is formulated and implemented by numerical nonlinear approximation of hysteresis loops, and then coupled with time-stepping finite element method to perform the analyses of both static and transient flux-regulatable characteristics. The preciseness of the coupling solution and the validity of machine design are verified by experimental results.

A Variable-Flux Hybrid-PM Switched-Flux Memory Machine for EV/HEV Applications

In this paper, a novel topology of hybrid-permanent-magnet switched-flux memory machine (HPM-SFMM) is proposed, which is characterized by a conventional SFPM machine with embedded “V”-shaped Al-Ni-Co magnet poles. The proposed machine combines the distinct synergies of torque enhancement in neodymium-iron-boron (NdFeB) PM and flux variability in aluminum-nickel-cobalt (AlNiCo) PM. By changing the magnetization directions of Al-Ni-Co magnets, the wide-speed-range high-efficiency operation can be readily achieved, which is highly favorable for automotive applications. The configuration and operating principle of the machine are first described, and the combination of stator/rotor pole numbers is optimized. In addition, the torque density/flux adjusting capability as the functions of dual-magnet dimensions are analytically derived. The magnet hybridizing proportion is optimized in order to achieve a favorite tradeoff between flux adjusting range and torque density improvement. Then, the electromagnetic performance of the proposed HPM-SFMM is investigated. Finally, a 12/14-stator/rotor pole prototype is fabricated to experimentally verify the analysis.