Young-Kyoun Kim

Optimization for reduction of torque ripple in interior permanent magnet motor by using the Taguchi method

This paper deals with two types of interior permanent magnet (IPM) motors, S-type and V-type. The V-type is optimized in the rotor shape to obtain better performance than the S-type. In general, average operational torque (AOT) and torque ripple of IPM motors are greater than those of other permanent magnet motors due to reluctance torque. This reluctance torque is generated by permanent magnet arrangement in the rotor of IPM motor and causes noise and vibration. Therefore, this paper presents the optimal V-shape, based on the finite-element method, of permanent magnet in the V-type by robust design, called Taguchi method, to reduce torque ripple and improve the ratio between torque ripple and AOT than S-type.

Loss distribution of three-phase induction motor fed by pulsewidth-modulated inverter

This paper deals with the loss distribution in a three-phase induction motor fed by a pulsewidth-modulated (PWM) inverter. The copper losses in the stator winding and rotor conductor bar, and iron loss except for mechanical and stray load losses, are computed by the variable time-stepping finite-element method (FEM) considering the switching action of the PWM inverter. The iron loss is evaluated by the frequency analysis of the magnetic flux density distribution using discrete Fourier transforms (DFT) and iron loss curves, which are provided by the manufacturer. Simulation results by the presented method are verified by the experiment results. Finally, the loss distribution of the PWM inverter type three-phase induction motor is compared with that of the conventional three-phase induction motor that is directly fed by the sinusoidal three-phase voltage source without any control devices.

A Novel Rotor Configuration and Experimental Verification of Interior PM Synchronous Motor for High-Speed Applications

On account of high efficiency and high power density, permanent-magnet synchronous motors (PMSMs) are mainly applied to a high-speed machine. Especially, because of relatively easy magnetic circuit design and control, a surface-mounted PMSM of them is adopted in almost the entire high-speed applications. However, the surface-mounted PMSM has some weak points due to a sleeve, which is nonmagnetic steel used in order to maintain the mechanical integrity of a rotor assembly in high-speed rotation. The sleeve causes additional eddy current loss in the rotor besides permanent magnet and increases not only magnetic air-gap length but manufacturing costs by raw material purchase and shrink fitting. Thus, in this paper, a new rotor shape for a high-speed interior permanent-magnet synchronous motor (IPMSM) is presented in order to resolve the faults of the surface-mounted PMSM. Moreover, the amount of permanent magnet employed in the IPMSM is decreased by approximately 53% than that of the surface-mounted PMSM. Except for the rotor configuration, all design conditions of the IPMSM are identical compared with the surface-mounted PMSM. Finally, the IPMSM is fabricated, and its superiority and reliability in high-speed operation are verified by test.

Optimal design of slotless-type PMLSM considering multiple responses by response surface methodology

This paper shows the usefulness of response surface methodology (RSM) for optimal design considering multiple responses. Moreover, full factorial design, one of the experimental design methods, is proposed to establish more reasonable and objective design area for applying RSM. The slotless-type permanent-magnet linear synchronous motor is optimized to develop larger average thrust and lower thrust ripple than the prototype, and the optimally designed one is manufactured. In the end, all analysis results are obtained by space harmonic method for fast and efficient design, and the validity of the results is verified by comparison with finite-element analysis and test

Optimal Design for Noise Reduction in Interior Permanent Magnet Motor

This paper presents methods to reduce acoustic noise in an interior permanent-magnet motor during the design stage. Mechanical and magnetic sources are considered to reduce noise of the machine, and structural and electromagnetic designs are performed. In the structural-design stage to reduce mechanical source, the structural resonances are moved to higher frequency for enhancement of stiffness. Then, in the electromagnetic-design stage to reduce exciting forces, the harmonic amplitude of magnetic forces and torque ripple are reduced by using an optimal design method, respectively. Two models are designed according to each objective function, and the validity of the design process and objective functions is confirmed by their simulated and experimental results.

Temperature Estimation of IPMSM Using Thermal Equivalent Circuit

This paper deals with the temperature estimation of interior permanent magnet synchronous motor (IPMSM). A thermal equivalent circuit of IPMSM is proposed with considering eddy current loss of PM as well as core losses of rotor. Heat sources, which are core loss of stator/rotor core and eddy current loss of PM, are calculated by numerical method to enhance the accuracy of thermal estimation. The thermal equivalent model is represented by the thermal resistances and thermal capacitances, which are determined by motor configuration. Meanwhile, a temperature test is performed using prototype to determine the heat transfer. Finally, this thermal equivalent model is verified by a temperature test in a 25 kW 12-pole/18-slot IPMSM.

Torque characteristic analysis considering the manufacturing tolerance for electric machine by stochastic response surface method

Manufacturing tolerances as well as measuring errors have a great influence on products designed by optimization technique, etc., to improve their characteristics and reduce the production cost. Therefore, tolerance analysis technique is required to find the tolerance band of design variables for minimizing the effect and estimating the characteristic distribution of the products. This paper represents the torque characteristics considering the manufacturing tolerance of an electric machine. In order to analyze the tolerance of the brushless DC (BLDC) motor, stochastic response surface methodology (SRSM), which treats input data as stochastic variables, is introduced. It can analyze the tolerances from the electrical point of view and find a robust optimal solution that has insensitive performance on its change of the design variables by applying the optimization technique. A surface permanent-magnet BLDC motor is used to confirm the validity of this method. It must be noted that the statistical torque characteristics analyzed by SRSM has a great advantage in the design and manufacture stage over conventional method.

Vibration reduction of switched reluctance motor by experimental transfer function and response surface methodology

This paper deals with the vibration analysis and the optimal control for the vibration reduction in a switched reluctance motor (SRM). To predict the vibration caused by the magnetic force, the experimental transfer function is coupled with the electromagnetic finite-element method. And then, based on the analysis method, the response surface methodology is applied to find the optimal point for reducing the vibration according to switching angles. The computed results are compared with some of the experimental results of a real SRM.

Approach to the shape optimization of racetrack type high temperature superconducting magnet using response surface methodology

Abstract This paper presents the optimization via shape design of the field coil using high temperature superconducting generator (HTSG). Response surface methodology (RSM) is applied to this optimizing process and well adapted to make an analytical model. In addition, it is easy to approach and efficient in seeking an optimal condition for a complex problem considering a lot of interaction of these design variables in an unknown system. I c in HTS materials is more sensitive to magnetic fields directed along the c axis of the unit cell ( B ⊥ ) than to fields in the ab plane [J.F. Picard et al., IEEE Trans. Appl. Supercon. 9 (2) (1999) 535]. Thus, in the shape design of the HTS magnet, the design to reduce the maximum B ⊥ should be considered in order to maintain the stability and substantial improvement on the performance. The optimal condition of the magnet shape, which is used for the field coil of HTSG, is obtained from the response surface made by RSM, and the effects of design variables related to the magnet are analyzed through the variance analysis. Moreover, the result of RSM is verified by comparison with those experimental results.

Structural and Magnetic Properties of Co Doped CeO

Nanoparticles of Ce1-xCoxO2 diluted magnetic semiconductors have been prepared by co-precipitation method. Effect of Co substitution has been studied using X-ray diffraction (XRD), transmission electron microscopy (TEM) and DC magnetization measurements. XRD pattern demonstrate that all samples exhibit single phase polycrystalline behavior. The full width at half maximum (FWHM) calculated from XRD pattern has been found to decrease with increase in the Co contents, indicating that particle size decreases with increase in the Co concentration. TEM micrograph reflects the nano-crystalline behavior of all the samples and shows that doping of Co ions hinders growth of the particles. DC magnetization measurements performed at different temperature reveals that Co doped CeO2 exhibits room temperature ferromagnetism.