Heyun Lin

Permanent Magnet Demagnetization Physics of a Variable Flux Memory Motor

The finite-element method incorporating with a hysteresis model has been used to analyze the variation characteristics of flux density of permanent magnets (PM) in the variable flux memory motor (VFMM). It accounts for the local hysteresis curves of PMs under different remagnetizing magnetomotive forces. Excellent agreement between the FEA predicted and measured phase back EMFs and air gap flux per pole has been achieved. It shows that the analysis method is suitable for evaluating the PM remagnetizing state in VFMM machines, and the remagnetization of PM is more difficult than the demagnetization, several times the full demagnetizing MMF is required in order to achieve the full remagnetization of PM.

A Novel Dual-Stator Hybrid Excited Synchronous Wind Generator

This paper presents a novel dual-stator hybrid excited synchronous wind generator and describes its structural features and operation principle. The no-load magnetic fields with different field currents are computed by 3-D finite-element method. Static characteristics, including the flux-linkage and EMF waveforms of stator windings, and inductance waveforms of armature windings and field winding, are analyzed. The simulation results show that due to the dual-stator structure, the air-gap magnetic flux can be easily controlled, while the output voltage can be increased effectively. Tests are performed on the prototype machine to validate the predicted results, and an excellent agreement is obtained.

Design and Analysis of a Novel Hybrid Excitation Synchronous Machine With Asymmetrically Stagger Permanent Magnet

A novel hybrid excitation synchronous machine with asymmetrically stagger permanent magnet (ASHESM) is developed. Its structure and field control principle are described and design equations are derived. Three-dimensional finite element analysis is used to obtain the no-load magnetic field distributions and field control capability under different field currents. A 1-kW prototype machine is designed, manufactured, and tested. The measured results agree well with finite element predictions. It shows that the flux of the prototype machine can be adjusted over a wide range with a relatively low field current.

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.

Transient Co-Simulation of Low Voltage Circuit Breaker With Permanent Magnet Actuator

A new type of low voltage circuit breaker with permanent magnet (PM) actuator is proposed. The magnetic field is computed using finite element method (FEM) to find out the relationship among the flux linkage, displacement and different currents and these information are stored in a look-up table. The control model, which is built in Matlab, is connected with the Adams model via input and output interfaces. The transient co-simulation is used to study the making process. Experiments are carried out on a prototype to validate the proposed method.

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.

Magnetic Field Analysis and Dynamic Characteristic Prediction of AC Permanent-Magnet Contactor

This paper reports a thorough investigation into the magnetic field of an ac permanent-magnet contactor and its control principles. Such contactors offer many advantages over conventional electromagnetic contactors in terms of energy saving and reliability. The simulation model, which couples the interaction of the magnet, circuit, and motion, is synthesized using MATLAB software. In order to speed up the simulation process, the model computes the nonlinear relationships of displacement, flux linkage, and current separately, using the finite-element method. We report simulation results for various phase angles of current flowing in the full bridge rectifier at full voltage. We have validated the calculated static force and the dynamic simulation experimentally.

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.