Han-Wook Cho

Design and Analysis of a High-Speed Brushless DC Motor for Centrifugal Compressor

This paper describes the design and analysis of a high-speed and high-power density BLDC motor for a 50-kW, 70 000-rpm class centrifugal compressor. Design criteria and power loss analysis of the high-speed machine structure are described by analytical method, and the results are validated by finite element method. And then, the prototype machine has been fabricated and tested. The experimental results confirmed the validity of the proposed design and analysis scheme of the high-speed BLDC motor

Analysis and experimental verification of moving-magnet linear actuator with cylindrical Halbach array

This paper deals with analysis and experiments of moving-magnet linear actuators with cylindrical Halbach arrays. On the basis of analytical two-dimensional field solutions, this paper predicts magnetic fields, thrust, flux linkage, and back electromagnetic fluctuation. The results are validated extensively by comparison with finite element analysis. Test results such as thrust measurements are also given to confirm the analysis.

Design Considerations of EM-PM Hybrid Levitation and Propulsion Device for Magnetically Levitated Vehicle

This paper deals with the design considerations of electromagnet/permanent magnet (EM-PM) hybrid levitation and propulsion device for magnetically levitated (maglev) vehicle. The machine requires PMs with high coercive force in order to levitate the vehicle by only PMs, and propulsion force is supplied by long-stator linear synchronous motor (LSM). The advantages of this configuration are an increasing levitation airgap length and decreasing total weight of the vehicle, because of the zero-power levitation control. Several design considerations such as machine structure, manufacturing, and control strategy are described. Moreover, this paper proposes the novel translator structure with segmented U-shape magnets for easy manufacturing. In order to verify the design scheme and feasibility of control strategy, dynamic test set is implemented and tested.

The influence of magnetization pattern on the rotor losses of permanent magnet high-speed machines

This paper deals with the comparison of two types of permanent magnet high-speed machines. Specifically, the effect of permanent magnet magnetization pattern on the rotor losses is investigated. On the basis of analytical field analysis and two-dimensional (2-D) finite-element method, this paper predicts the flux harmonics and rotor losses under no-load condition. It is shown that the Halbach magnetization is superior to parallel magnetization in terms of producing rotor losses.

Analytical Torque Calculations and Experimental Testing of Permanent Magnet Axial Eddy Current Brake

This paper discusses the braking torque and normal force analysis of axial flux permanent magnet (AFPM)-type eddy current brakes (ECB) on the basis of an analytical field computation using a space harmonic method. On the basis of the magnetic vector potential and a 2D polar coordinate system, permanent magnets considering the eddy current effect are obtained. Additionally, by utilizing the derived analytical field solutions, the braking torque and normal force are predicted. Finite element analysis is employed to confirm the validity of the analysis and compare it with the experimental results obtained from the prototype AFPM-type ECB.

Analytical Prediction and Measurements for Inductance Profile of Linear Switched Reluctance Motor

This paper describes analytical prediction and measurements for the inductance profile of a linear switched reluctance motor (LSRM). First, analytical solutions for flux density due to mover winding currents are derived, for the case when the mover is located at aligned and unaligned positions. Then, using the inductance at aligned and unaligned positions obtained from two-dimensional (2-D) analytical solutions and Fourier series expansion proposed in this paper, we predict the inductance profile of the LSRM analytically. Finally, inductance measurements are given to confirm the analysis

Thrust analysis and measurements of tubular linear actuator with cylindrical halbach array

This paper deals with design and analysis of the moving-magnet linear actuator with cylindrical Halbach array. On the basis of two-dimensional (2-D) finite-element analysis, this paper predicts thrust characteristics according to design parameters such as magnet height, air-gap length, coil thickness, and pole number. Then, we manufactured equipment made on an experimental basis of moving-magnet linear actuator with cylindrical Halbach array by employing parameters obtained from design results. Finally, this paper presents test results such as thrust measurements, which are given to confirm the finite-element analysis, according to load current and mover position.

Dynamic characteristic analysis and experiments of moving-magnet linear actuator with cylindrical Halbach array

This paper deals with the dynamic characteristic analysis and experiments of moving-magnet linear actuator with cylindrical Halbach array. On the basis of two-dimensional analytical solutions and experiments, control parameters are obtained. Then, a dynamic simulation algorithm is established from a voltage and motion equation. Finally, for various values of frequency, dynamic simulation results for characteristics of voltage, current, and displacement of moving-magnet linear actuator are presented and confirmed through the experiments.

Zero-power control of magnetic levitation vehicles with permanent magnets

This paper deals with the zero-power control of magnetic levitation (maglev) vehicles that use permanent magnets as well as electromagnets for levitation. The nominal load is levitated by permanent magnet and the current consumption for stable levitation can be reduced. In order to guarantee the tracking capability, the proposed controller is based on the state feedback controller and modified to balance attraction force and total weight. The commanded voltage is used instead of the coil current in the feedback loop so that the current measurement can be avoided. A full-scale hybrid maglev tester was constructed and some experiments were carried out to show the performance of the proposed method.

Dynamic Performance Evaluation of 5-DOF Magnetic Levitation and Guidance Device by Using Equivalent Magnetic Circuit Model

In this paper, the dynamic performance evaluation of a 5-degree of freedom (DOF) magnetic levitation and guidance device is addressed. In particular, the electromagnetic forces from an equivalent magnetic circuit model are coupled to a 5-DOF dynamic motion model of the device. With the proposed model, dynamic behaviors are simulated by considering the dynamic interactions between levitation and guidance elements while both systems are operating. In addition, the experimental system is successfully tested and stable levitation and guidance is demonstrated at the desired operating gap and unexpected disturbance forces.