• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.12
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• pp.709-717
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• 2004

Flux-reversal machine (FRM) is a new brushless doubly salient permanent magnet machine. Its operation is similar to that of the brushless DC motor, so it can be driven by 120 degree square wave voltage and use PWM pulse patterns in two-phase feeding scheme to control the speed. In this driving method, the back electromotive force (BEMF) current in the open phase is generated by the BEMF. It can be appeared or disappeared according to the changes of the neutral voltage of the machine. In this paper, the time-stepped voltage source finite-element method taking BEMF current into account is proposed. Its influences on the performances of the FRM are also investigated. To prove the propriety of the proposed analysis method, a Digital Signal Processor (DSP) installed experimental devices are equipped and the experiment is performed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.7
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• pp.459-462
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• 2017

In this study, we design, model, and analyze a compound generator that combines the axial flux permanent magnet (AFPM,) and radial flux permanent magnet (RFPM), which is expected to increase power generation by allowing the magnets to be placed on the upper, lower, left, and right sides of the same-sized generator. Through the design, modelling, and analysis of AFPM and RFPM compound generators, the generator load evaluation results rated output of 500.25 W and efficiency of 87.60%, respectively, at a rated speed of 600 rpm. By employing this complex generation system,these findings are expected to contribute to the activation of a small power generation system.

• Journal of Magnetics
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• v.20 no.4
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• pp.405-412
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• 2015

In this study, we describe the effects of changing the magnet shape of permanent magnets (PMs) in a rotor Halbach-array PM generator for reciprocating free piston generator applications. More specifically, the rectangular-shaped magnets were replaced by the trapezoidal-shaped magnets. The initial design, an analytical magnetic field solution of rectangular shaped magnets, is presented and air-gap magnetic flux density and thrust force were estimated. The results were compared to the finite element analysis (FEA) showing excellent agreement. Using FEA, the effect of the shape of the magnets on the flux density and thrust force waveforms is analyzed. Moreover, the proportion of the Halbach array in the machine was optimized by the means of a parametric search. The results obtained from the analytical calculations and FEA were validated by comparing to those of Radial-array PM generator.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1402-1408
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• 2010

Interior Permanent Magnet Synchronous Motor(IPMSM) produces two kind of torque that Magnetic and Reluctance torque. The permanent magnet linkage flux Ψa and d-axis and q-axis inductance have an important influence on the torque characteristic of IPMSM. Thus their accurate prediction is essential for predicting performance aspect such as the torque and flux-weakening capabilities. In this paper, we compared the characteristic parameters and operation region of two type IPMSM which has different pole numbers.

• Journal of Aerospace System Engineering
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• v.2 no.3
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• pp.24-28
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• 2008

Eddy current are induced when a nonmagnetic, conductive material is moving as the result of being subjected to the magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and conductor. Using this concept, eddy current damping can be used as a form of viscous damping. This paper investigated analytically and experimentally the characteristics of an eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of the eddy current damping is developed from electromagnetics and is verified from Maxwell program and experiments. From these comparisons, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies. In order to improve the prediction of the characteristics of an eddy current damping, the induced magnetic flux densities have to be considered in following researches.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.966-967
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• 2008

2kW급 선형 압축기용 액츄에이터로 직선 왕복 운동을 동작하게 하기 위하여 2상 영구자석형 횡자속 선형 전동기(Permanent Magnet Transverse Flux Linear Machine; PM-TFLM)와 스프링을 조합하여 선형 공진 시스템을 구성하였다. 선형전동기의 이동자를 공진점부근에서 왕복 운동을 하기 위해서 빠른 왕복 운전과 적절한 운전 알고리즘이 필요하게 된다. 먼저 2상으로 이루어진 PM-TFLM의 순시 토오크 제어를 위하여 벡터 제어 알고리즘을 설계하여 구현하고 피스톤, 스피링 및 부하에 따라 운전제어를 수행하는 방법에 대하여 연구를 하였다. 종래의 3상 교류 전동기의 순시 토오크 제어에 적용하는 벡터제어 알고리즘을 2상 PM-TFLM에 적용하여 그 타당성을 보이고 빠른 왕복운전을 안정적으로 수행함을 실험을 통하여 입증하였다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.83-84
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• 2015

In order to use the high-speed range of Interior Permanent Magnet Synchronous Motor(same as IPMSM above), the motor should be at flux weakening control status. High-speed range is called field weakening control region or constant power region, and explain the basic theory of flux weakening control used in the constant power region. Back electromotive force of IPMSM is measured. and field weakening conrtrol driving characteristics is configurated verification test. Through experimentation speed-torque characteristic curve, the efficiency variation corresponding to the current phase angl,the efficiency map were produced.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.618-621
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• 2008

The magnetic recording system shows the difference of the magnetic recording density according to the direction of the magnetic field. The yoke shape of the recording system affects the magnetic field direction; therefore, the recording density may be raised by changing the shape. This paper intends not only to increase the magnetic flux density of the record region but also to reduce the recording loss of a specific region through the simultaneous design of the yoke and the magnet. The recording loss can be reduced by minimizing the magnetic flux of the adjacent area to the recording region. The topology optimization method is used to obtain the optimal shape both of the yoke and the magnet. And the commercial package, Maxwell is used to verify the result.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.2 s.179
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• pp.172-180
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• 2006

Although there existed many types of manual/power hybrid wheelchairs, their use was not widespread because of their inconvenience in converting drive system and in folding frames. To carry a wheelchair in the car or to convert driving methods, some hard work of disassembling or exchanging wheels was required for most of currently available hybrid wheelchairs. In this study, the standard foldable manual wheelchair was reformed to a power wheelchair by installing the newly developed Axial Flux Permanent Magnet(AFPM) type of brush less direct current(BLDC) motor on each rear hub of wheelchair. This wheelchair could be driven by manual or electric power without exchanging. wheels, thus no additional work was needed for carriage or for power conversion. The developed wheelchair was evaluated for durability, stability, maneuverability, cost, and reliability in accordance with the Korean standards. The results indicated that the developed hybrid wheelchair was good enough for commercialization comparing to other imported wheelchairs.

• Journal of Magnetics
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• v.21 no.1
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• pp.78-82
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• 2016

Cogging torque will affect the performance of a permanent magnet Brushless DC Motor (BLDCM), thus the reduction of cogging torque is key for BLDCM optimization. In this paper, the phase shifting of cogging torque for a fractional-slot concentrated winding BLDCM is analyzed using the Maxwell tensor method. Moreover, a 9-slot 10-pole concentrated winding BLDCM driven by ideal square waveform is studied with the finite element method (FEM). An effective method to reduce the cogging torque is obtained by adjusting the slot opening. In addition, the influences of different slot openings on back electromotive force (back-EMF), air gap flux density and flux linkage are investigated and experimentally validated using the prototype BLDCM.