• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 1991년도 추계학술발표회논문집
• /
• pp.75-79
• /
• 1991

In this study, a new sinusoidal PWM inverter suitable for use with power MOSFETs is described. The output waveforms in the proposed OWM inverter are investigated both theoretically and experimentally. A modulating signal for the three-phase PWM inverter is obtained by adding 3nth harmonics to the conventional three-phase sine wave. By using the new modulating signal, the amplitude of the fundamental component is increased about 15 percent more than that of a conventional sine wave inverter and the commutation number of the inverter is decreased to two-thirds of a conventional one.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.924-926
• /
• 2001

This paper presents the characteristics of current harmonics and torque ripple of Brushless DC motor, which is developed the fan blower of vehicles, according to permanent magnet shape input voltage wave form. To investigate the torque ripple and the phase current harmonics, these characteristics is analysed and compared the experimental results. In the process of analysis, FEM is introduced and computed a transient state torque of BLDC with a sinusoidal and a PWM wave voltage.

• 한국음향학회:학술대회논문집
• /
• 한국음향학회 1999년도 학술발표대회 논문집 제18권 1호
• /
• pp.303-306
• /
• 1999

The paper describes a theoretical study on the speed of the torsional elastic waves propagating in a circular cylinder whose outer radius varies periodically as a harmonic function of the axial coordinate. The approximate solution for the phase speed has been obtained using the perturbation technique for sinusoidal modulation of small amplitude. It is shown that the wave speed in the cylinder with a corrugated outer surface is less than that in a smooth cylinder by the square of the amplitude of the surface perturbation. This theoretical prediction agrees reasonably with an experimental observation reported earlier. It is also shown that the wave speed reduction due to the surface corrugation becomes larger for a thinner cylinder and for a bigger density of corrugation.

• 대한전자공학회논문지
• /
• 제9권5호
• /
• pp.12-18
• /
• 1972

정현 신호 및 zero 평균 정상 정규 잡음의 협대역파 신호를 갖는 n차 반파 zero기억형 비선형 장치의 출력 SN 비 및 m차 고조파 발생의 관계를 밝혔다. 최대 출력 SN비는 소 신호 입력에서 m=n=2 이었으며 대 신호 입력에선 항시 n=2이었다.

• Journal of Power Electronics
• /
• 제9권2호
• /
• pp.173-179
• /
• 2009

This paper proposes a new three-phase diode rectifier system with a sinusoidal input current at unity power factor and a regulated and isolated output voltage at low level. The inherent natural wave-shaping capability of the reduced kVA polyphase transformer together with an active current wave-shaping technique results in a significant reduction of input and output filter requirements associated with switching ripple and EMI. The operation principles are described along with a design example and a comparative evaluation. Experimental results on a 1.5kW prototype are provided to validate the proposed concept.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 A
• /
• pp.398-402
• /
• 1999

In PWM inverter fed traction motor drive systems, the switching frequency is restricted and thus the electromagnetic acoustic noise is generated. To reduce such an audible noise, we propose the modified RSF(Randomized Switching Frequency)-PWM method. In the proposed RSF-PWM method, both triangular wave and sawtooth wave are used in one period as carrier waves. Because the proposed method has inherently the same property as sinusoidal PWM method, there is no problem of linearity. To verify the validity of the modified RSF-PWM method, computer simulations are carried out.

• 한국광학회지
• /
• 제4권1호
• /
• pp.73-83
• /
• 1993

광굴절결정에 구형과 및 저현파형의 외부 전장을 인가할 때 유기되는 공간 전하장의 시간 종속 해를 해석적으로 유도하였다. B$i_{12}$Si$O_{20}$ 결정에 최대 7KV/cm (주파수<1KHz)의 전장을 가하면서 시간 종속적인 2광파 혼합의 이득 변화를 측정하고 이론치와 정량적으로 비교 분석하였다.

• 전기학회논문지
• /
• 제58권5호
• /
• pp.976-981
• /
• 2009

This paper proposed optimal design and microcontroller driver for driving the thin-type ultrasonic motor. To find the optimal size of the stator, motions of the motor were simulated using ATILA by changing length, width and thickness of the ceramics. Two sinusoidal waves which have 90 degree phase difference were needed for driving the thin-type motor. The thin-type ultrasonic motor driver was composed of microcontroller(Atmega128), push-pull inverter, encoder and AD-converter. Microcontroller generates four square waves which have variable frequency and 25[%] duty ratio in $20{\sim}150$[kHz]. The output signals of microcontroller were converted to sine wave and cosine wave by push-pull inverter and were applied to the thin-type ultrasonic motor. The encoder and AD-converter were used for maintaining speed of the thin-type ultrasonic motor. The AD-converter controlled DC voltage of inverter in accordance with output signal of encoder. Using the driver, characteristics of the motor as speed and torque were measured.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 A
• /
• pp.453-455
• /
• 1993

In this research, the digital signal processing PC board which employs TI's TMS320C25 is implemented. The board can perform following functions. spectrum analysis of speech and repetitive signal, digital filters emulation by convolution, signal generation of sinusoidal wave, rectangular wave etc.. In this system, communications between PC and DSP board. program down-loading to DSP board and recording and graphic of acquired and processed data in DSP board are executed by PC. Parallel interface and buffer memory are used in communications. Data acquisition and operation are carried out in DSP board. Resultant data are transmitted to PC and output through DAC.

• 한국해안해양공학회지
• /
• 제8권1호
• /
• pp.44-51
• /
• 1996

해안선에서 장파의 처오름높이의 정확한 산정은 공학적인 측면에서 매우 중요하다. 본 논문에서는 크노이드파 이론을 이용하여 장파의 처오름높이에 관한 연구를 하였다. 크노이드파는 파형이 복잡하여 발생과 처오름높이 산정이 매우 어렵다. 본 연구에서는 경계요소법을 이용하여 급경사 지형에서 크노이드파의 처오름높이를 계산한다. 일반적으로 크노이드파의 처오름높이는 동일한 파고를 갖는 고립파의 처오름높이보다는 작지만, 동일한 파고와 파장을 갖는 정현파의 것보다는 항상 크다. 크노이드파의 처오를높이는 또한 파장이 상대적으로 짧을 경우에는 파장에 따라 단순히 증가하지 않으며, 파장이 매우 커지면 고립파의 처오름높이에 점근적으로 접근한다. 경계요소법에 의해 계산된 크노이드파의 처오름높이는 기존의 수리실험 결과와 대체로 일치한다.