Kyung-Ho Ha

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.

Stator pole and yoke design for vibration reduction of switched reluctance motor

This paper investigates the influence of various stator pole shapes and yoke structures in switched reluctance motors (SRMs) on the mechanical behavior caused by the electromagnetic force. The stator part in SRM produces most vibration. The geometric design of the stator is therefore necessary to reduce the vibration. Based on electromagnetic and structural finite element method (FEM), the free and forced vibrations for the various structures of SRM with 6/4 poles are analyzed. Then a less vibration stator structure is proposed. Some numerical computations for a prototype motor are verified by experimental results.

A study on iron loss analysis method considering the harmonics of the flux density waveform using iron loss curves tested on Epstein samples

This paper deals with a study on an iron loss analysis method in the single-phase line-start permanent magnet synchronous motor. The iron loss is affected by the time rate of the change of magnetic flux density at the motor cores. The distribution and changes in magnetic flux densities of the motor are computed by using a two-dimensional finite element method. Discrete Fourier Transform (DFT) is used to analyze the magnetic flux density waveforms in each element of the analysis model. Iron losses in each element are evaluated using iron loss curves tested by an Epstein test apparatus. The total iron loss can be obtained by the summation of the iron losses in all the elements.

Design and characteristic analysis of non-contact magnet gear for conveyor by using permanent magnet

This paper deals with the design of noncontact magnet gear for conveyors. The magnet gear, consisting of two permanent magnets with skew, is a device for changing the transmission for direction without the mechanical contact between two magnets. To perform a parametric study, the important design variables related to the permanent magnet are selected, and then the influence of the design parameters on the magnetic torque performances is investigated. The 3-dimensional electromagnetic finite element method (FEM) is used for the characteristic analysis. Based on these results, the magnet gear is designed and verified by comparing the analysis result with the experimental data.

Loss Distribution of Three-Phase Induction Motor and BLDC Motor According to Core Materials and Operating

This paper deals with the loss distribution of a three-phase induction motor (IM) and a BLDC motor considering operating point-of-core material based on the FEA and experiments. In order to increase motor efficiency, a high grade of core material can be used. However, sometimes it decreases or provides no improvement of efficiency. This is due to the fact that high-grade core materials generally have lower saturation flux density and core loss. Therefore, when operation of point-of-core materials is in a high-saturation region with low frequency, there could be no significant improvements or decrease of efficiency. The presented results give guidelines to selecting core materials to improve motor efficiency.

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.

Dynamic rotor eccentricity analysis by coupling electromagnetic and structural time stepping FEM

The influence of unbalance forces in rotary electric machines on the rotor vibration behavior is investigated in this paper. The dynamic response of a Switched Reluctance motor (SRM) rotor is analyzed by the coupled structural and electromagnetic Finite Element Method (FEM) in the transient state solved in a step-by-step procedure with respect to time. The proposed procedure allows solving the coupled field. The dynamic behavior of rotor caused by the coupled mechanical and magnetic forces is presented, according to the variation of unbalance mass and bearing stiffness.

Orbital analysis of rotor due to electromagnetic force for switched reluctance motor

The purpose of this paper is to analyze the orbital response of rotor due to unbalanced electromagnetic force for switched reluctance motor (SRM). In order to reduce vibration of SRM, it is necessary to predict the mechanical dynamic behavior of the rotor-bearing system. So the orbit of the rotor according to rotation speed is analyzed by using the finite element method (FEM), and unbalanced electromagnetic force induced by dynamic eccentricity is calculated by the Maxwell stress tensor. From the results, the stability behavior of the rotor caused by unbalanced electromagnetic force is evaluated.

A study of the design for touch free linear eddy current brake

This paper describes the performances of eddy current brake according to the design parameters. The characteristics are analyzed by using 2-dimensional Finite Element Method (2-D FEM) in order to predict the effect of the design parameters. The magnet stack width is determined from equivalent stack width that is calculated by solution of the field with scalar potential. The validity of available calculation program with FEM is achieved by comparing with experimental value. From the results, the optimized magnet configuration of the eddy current braking system is designed to obtain not only the maximum braking force but also the minimum attraction force.

Mechanical vibration and stress analysis of the link of interior permanent magnet type synchronous motor

This paper deals with stress analysis of the link and rotor vibration for interior permanent magnet type synchronous motor, which result from mechanical weakness coupled with electromagnetic forces. The electromagnetic force is calculated by equivalent magnetizing current (EMC). In addition, the natural frequency and mode shape of rotor are briefly analyzed through the transfer matrix method (TMM) and compared with experiments. Using the results of these stress and mechanical behavior analysis, mechanical safety in the link and critical speed are studied.