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권중학(Kwon, Joong-Hak),김광석(Kim, Kwang-Suk),이창민(Lee, Chang-Min),황상문(Hwang, Sang-Moon) 한국소음진동공학회 2009 한국소음진동공학회 논문집 Vol.19 No.8
The goal of this study is to examine the effect of the number of slots on the noise from BLDC motors. To this end, the number of poles was fixed to 4 and the number of the slots was set to 6 or 24 before noise was measured. Motors having different numbers of slots showed clear differences in noise. Cogging torque, torque ripple and normal local force were interpreted, analyzed and compared to determine the reason for the differences. To determine the cause of the noise, cogging torque, torque ripple and normal local force were calculated, which are representative noise sources of BLDC motors, and FFT was performed to analyze their frequency components(harmonics). The results show that torque ripple and normal local force were the dominant factors in the noise difference between the 6-slot and 24-pole motors. As the number of the slots increased, the number of harmonics decreased and their amplitude of harmonic were reduced, which was attributed as the reason for the noise differences.
권중학(Kwon, Joong-Hak),김광석(Kim, Kwang-Suk),방기창(Bang, Ki-Chang),황상문(Hwang, Sang-Moon) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.4
With the advent of mobile phone, digital multimedia broadcasting(DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion(THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.
Analysis of total harmonic distortion in microspeakers considering coupling effect
이창민,권중학,황상문 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.9
With the advent of the mobile phone, Digital Multimedia Broadcasting (DMB) service for multimedia data communication will soon be realized. With regard to the acoustic aspects of this service, a smaller and lighter microspeaker also soon will be implemented in MP3song players and speakerphones. The sound quality of such microspeakers, as evaluated with reference to total harmonic distortion (THD) is becoming more important. THD is the proportion of the higher-order frequency output response to a sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear responses of diaphragms. In this work, THD was analyzed in consideration of the coupling effects between mechanical vibration and electromagnetic exciting forces. Simulated THD results were compared with the experimental data. The THD in the lower frequency range increased due to the increased displacement of the voice coil and the elevated high-order component response of the sound pressure.
매입형 영구자석 전동기의 전자기력을 고려한 소음특성 분석
이홍주(Lee, Hong-Joo),권중학(Kwon, Joong-Hak),이창민(Lee, Chang-Min),황건용(Hwang, Gun-Yong),황상문(Hwang, Sang-Moon) 한국소음진동공학회 2009 한국소음진동공학회 논문집 Vol.19 No.5
Noise sources in electric machines are broadly categorized as magnetic, mechanical, electronic and aerodynamic. Especially, there are several kinds of noise sources due to the change of reluctance by rotor position in IPM motor. To separate acoustic noise by mechanical structure and electromagnetic sources, resonance frequency and the effect of vibration and acoustic noise by electromagnetic sources are analyzed. And then, the structural and electromagnetic designs to reduce acoustic noise are performed. The relevance about the study on noise reduction of IPM motor is verified by noise experiment, noise and vibration analysis.
김평호(P. H. Kim),권중학(J. H. Kwon),이종석(J. S. Lee),황상문(S. M. Hwang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
This paper is about design for minimum flux leakage in microspeaker used for radiotelegraph. Response Surface Method (RSM) is applied as the optimization technique high magnetic force. Object function are magnetic force and flux leakage as three factors. Pole piece thickness, magnet grade and yoke thickness which are selected in design of experiment. Magnetic force and flux leakage are calculated for each condition and optimized by results evaluated with RSM. When those factors are the thickness of pole piece of 0.9㎜ magnet grade of N42H and the thickness of yoke of 0.75 ㎜. Magnetic force is satisfied and flux leakage is decreased to 11.8%.
변형된 자기회로를 이용한 이동통신 단말기용 트랙형 마이크로 스피커 개발
박진훈(Park Jin-Hun),권중학(Kwon Joong-Hak),이창민(Lee Chang-Min),황상문(Hwang Sang-Moon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
With development of multimedia, space of many electronic components became more and more smaller because of large screen of cellular phone. It is difficult to maintain performance of microspeaker due to reduction of space of microspeaker also. In this paper, two types of elliptical speakers are introduced. that is, both inner and outer magnet have elliptical shape and outer magnet have only elliptical shape. Magnetic and Vibration analysis is performed using FEM, and compare to conventional and proposed types. Microspeaker that made up only outer elliptical magnet has the best performance, because of large magnet volume and low 1st resonance frequency. Also in this paper present optimum design method. of coil.
박진훈(Jin Hun Park),권중학(Jung Hak Kwon),황상문(Sang Moon Hwang) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.1
본 논문에서는 무전기에 사용되는 마이크로스피커의 누설자속을 최소화하는 설계에 초점을 맞추었다. 진동판표면으로 누설되는 자속을 저감시키고 전자기력을 향상시키기 위한 최적설계로 반응표면법을 적용하였다. 최적설계의 목적함수는 전자기력과 누설자속이며, 폴피스 두께, 마그넷 그레이드, 요크 두께의 세 가지 변수에 의해 결정되어진다. 전자기력과 누설자속은 반응표면법으로 각 조건에서 계산되었고, 평가된 결과에 의해 최적화되었다. 폴피스 두께 0.9 ㎜, 마그넷 그레이드 N42H, 요크 두께 0.75 ㎜ 일 때, 전자기력은 초기 모델과 동등한 수준을 만족하였고, 자속 누설량은 11.8% 저감되었다. This paper focuses on the design of microspeakers with minimum flux leakage, for use in radiotelegraphy. The response surface methodology (RSM) is applied as the optimization technique for obtaining a large magnetic force and a small flux leakage on diaphragm. The object functions of this optimization are the magnetic force and the flux leakage along three factors; pole piece thickness, magnet grade and yoke thickness, which are determined by the design of the experiment. The magnetic force and the flux leakage are calculated for each condition and optimized by results evaluated with RSM. For a pole piece thickness of 0.9 ㎜, a magnet grade of N42H and a yoke thickness of 0.75 ㎜, the magnetic force is satisfied as initial model and flux leakage is decreased to 11.8% than initial model.