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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.
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.
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.
황건용(Hwang, Gun-Yong),황상문(Hwang, Sang-Moon),권중학(Kwon, Joong-Hak),김광석(Kim, Kwang-Seok),이홍주(Lee, Hong-Joo) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.10
With the growth in electronics and the remarkable advance in wireless communication technology, mobile devices, such as mobile phones and PDAs are incessantly improved in their diverse functional performance. Lighter weight and smaller size has been gradually accomplished by recent circuit integration technology resulting in rapid growth in the number of mobile phone subscribers. Driven by customer demand, recent mobile devices are fully capable of realizing a variety of dazzling multimedia effects powered by electro-acoustic parts that have become one of the generic components. However, This paper also presents an oval micro-speaker, that is' expected to show an excellent performance within limited space of mobile phone, and its performance design has been suggested as well. Finally, a statistical approach to achieve high characteristic and performance is suggested by Taguchi method to identify a certain relationship between a mobile phone and a micro-speaker.
이동통신 단말기용 통합 영구 자석 형태의 마이크로스피커 개발
황상문(Hwang, Sang-Moon),이홍주(Lee, Hong-Joo),권중학(Kwon, Joong-Hak),황건용(Hwang, Gun-Yong),양용창(Yang, Yong-Chang) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.2
In mobile phones of multimedia era, microspeakers of high qualify sound are essential parts to generate human voice in speaker phone and MP3 song player. In this paper, two types of microspeakers, outer permanent magnet (PM) and combined PM type, are analyzed using electromagnetic, mechanical and their coupling analysis. For performance comparison, voice coil diameter is chosen as a design parameter to change excitation position and magnet volume for both types. For combined PM type, sound pressure level (SPL) is improved due to increased PM volume compared to outer PM type. Also, with the decreased voice coil diameter for combined PM type, the 1st resonant mode of the diaphragm is more efficiently excited due to concentrative excitation, resulting in lower and broader frequency range. Therefore, it can be said that the combined PM type microspeakers are more advantageous for high performance microspeaker which are essential for multimedia era.