Shuhua Fang

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.

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.

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.

A novel linear and rotary Halbach permanent magnet actuator with two degrees-of-freedom

This paper presents a novel linear and rotary Halbach permanent magnet actuator, which is capable of two degrees-of-freedom movements. The magnetic field distributions of the actuator are analytically analyzed using the magnetic scalar potential, where its tubular mover is transferred into a planar one by using a magnetic field curvature factor. The linear cogging force and rotary cogging torque and the stator flux-linkage of the actuator are subsequently predicted validated by the three-dimensional finite element method.

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.

Dynamic performance analysis of permanent magnet contactor with a flux-weakening control strategy

A new flux-weakening control strategy for permanent magnet contactors is proposed. By matching the dynamic attraction force and the antiforce, the terminal velocity and collision energy of the movable iron in the closing process are significantly reduced. The movable iron displacement is estimated by detecting the closing voltage and current with the proposed control. A dynamic mathematical model is also established under four kinds of excitation scenarios. The attraction force and flux linkage are predicted by finite element method and the dynamics of the closing process is simulated using the 4th-order Runge-Kutta algorithm. Experiments are carried out on a 250A prototype with an intelligent control unit to verify the proposed control strategy.

Static Characteristics of Novel Air-Cored Linear and Rotary Halbach Permanent Magnet Actuator

This paper investigates the static characteristics of a novel air-cored linear and rotary permanent magnet actuator (LRPMA) with a Halbach permanent magnet array. By the given magnetization distributions and boundary conditions in the cylindrical coordinate system, the magnetic field distributions of the actuator are analytically analyzed using the magnetic scalar potential and the modified BESSEL functions. A 3-D finite-element (FE) model is established to validate the correctness of the analytical results. Analytical linear electromagnetic force and rotary electromagnetic torque, respectively, are derived and verified using the FE method for the characterization and optimization design of the air-cored Halbach LRPMA.