• Proceedings of the KIPE Conference
• /
• 2005.07a
• /
• pp.774-777
• /
• 2005

In this paper, a constant frequency phase shifting PWM controlled voltage source full bridge-type series load resonant high-frequency inverter using the IGBT power modules is presented for innovative consumer electromagnetic induction heating applications such as a hot water producer, steamer and super heated steamer. The full bridge arm side link passive quasi-resonant capacitor snubbers in parallel with the each power semiconductor device and high frequency AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is discussed and evaluated on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency soft switching PWM inverter topology, what is called class DE type. including the variable-power variable-frequency(VPVF) regulation function can expand zero voltage soft switching commutation range even under low output power setting ranges, which is more suitable and acceptable for induction heated dual packs fluid heater developed newly for consumer power utilizations. Furthermore, even in the lower output power regulation mode of this high-frequency load resonant tank high frequency inverter circuit it is verified that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07b
• /
• pp.1149-1152
• /
• 2005

The frequency of inverters for driving multi-lamp backlights for LCD TV was synchronized to reduce noise from lamps and noise generated from PWM dimming.

• Proceedings of the KIEE Conference
• /
• 2004.07c
• /
• pp.1835-1837
• /
• 2004

The UHF electromagnetic waves excited by PD pulses propagate along the GIS busbar not only TEM mode, but also TE and TM mode. Generally the waves detected by the UHF sensors are those of high order modes and such waves can only propagate the higher than cut-off frequency. In this paper, computed cut-off frequency of 362[kV] GIS by each modes and simulated electromagnetic field of each propagation modes by FEM(Finite Element Method) program. Frequency band of each TEmn/TMmn modes were determinated by simulation results and were discussed optimal position of UHF sensor from this results.

• Proceedings of the KIPE Conference
• /
• 1998.07a
• /
• pp.423-427
• /
• 1998

A new single-switch, three-phase, high power factor, multi-resonant, ZCS buck rectifier that operates in the continuous conduction mode has been reported. Basically, pulse frequency modulation method should be adopted to suitably control the system. This paper puts main focus on the methods how the pulse frequency modulation can be implemented and a comprehensive investigation on the corresponding control loops is coducted.

• Journal of the Korean Ceramic Society
• /
• v.45 no.4
• /
• pp.208-213
• /
• 2008

In this study, helical antenna with microwave ZST ceramics was designed using finite element method and developed. Studied parameters are relative dielectric constant of the dielectric core and the width of the conduction metal band of the antenna. As shown in the results, the center frequency of the antenna was decreased as the dielectric constant increased. Also beam width of the antenna increased as both the dielectric constant and the conduction band width increased. Based on the designed optimal shape, the manufactured antenna has the good beam width at center frequency 1.58 GHz.

• Journal of the Optical Society of Korea
• /
• v.4 no.1
• /
• pp.11-13
• /
• 2000

We experimentally measured the cold cavity loss of a mode-locked erbium-doped fiber ring laser in situ by using the relaxation oscillation frequency method. The relaxation oscillation frequency is measured for various pumping powers and the data is fitted by the least squares method with a theoretical curve of parameters including the cavity loss. We obtained a cavity loss of 15.3$\pm$0.5 dB which was found to agree with the results of direct transmission loss measurements.

• Journal of Oriental Neuropsychiatry
• /
• v.21 no.4
• /
• pp.163-173
• /
• 2010

Objectives : The objective of this study was to assess the effects of acupuncture applied at 114 and Liv3 points on heart rate variability (HRV) in normal subjects under mental stress. Methods: 36 healthy male and female subjects were recruited and randomized to a treatment group(18 subjects) or a control group (18 subjects). After 10-minutes rest period and instrumentation, both groups performed a mental stress test(Stroop color word test, Arithmetic test. four rule of arithmetic task) for l6-minutes. HRV was recorded before and after the mental stress. And then acupuncture needles were inserted on 114 and Liv3 for the study group. In the control group, they rested for l5-minutes. And Heart rate variability(HRV) was measured. Results: In the both groups, low frequency(LF) power, normalized low frequency power(LF(norm)) and ratio of low frequency to high frequency(LF/HF) was significantly increased after mental stress. Acupuncture induced significant decrease in low frequency(LF) power, normalized low frequency power(LF(norm)) and ratio of low frequency to high frequency (LF/HF) which was increased after mental stress test. In contrast, control group induced no changes. Conclusions : Acupuncture on 114 and Liv3 could be useful to decrease sympathetic activity and prevent the alteration of autonomic nervous system due to mental stress.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.66 no.11
• /
• pp.1561-1567
• /
• 2017

This paper calculates the effective capacity of EES providing the primary frequency control service based on its contribution to the frequency response of the power system. The amount of governor response from conventional generators which can be replaced by the primary frequency control from EES keeping the frequency response of the power system is defined as the effective capacity. The proposed method for calculating the effective capacity of EES is verified through case studies employing Korean power system. Furthermore, the application of the effective capacity of EES to power system operation is also discussed.

• Journal of Sensor Science and Technology
• /
• v.17 no.4
• /
• pp.289-294
• /
• 2008

The purpose of this study is to materialize the viscosity sensor by using the SH-SAW sensor of which the center frequency is operated at higher than 50 MHz. In order to measure the viscosity, SAW sensor of which the center frequency is operated at 100 MHz is developed. By using the developed sensor, phase shift, delay time, insertion loss, and frequency variation are measured at different viscosity. The result shows that the phase shift difference between the viscosity variations is such that the difference between the distilled water and the 100 % glycerol solution is approximately $45^{\circ}$, the change of the insertion loss is approximately 9 dB, and the difference of frequency variation is approximately 5.9 MHz. Therefore, it is shown that viscosity of unknown solution can be measured with the surface acoustic wave sensor.

• Journal of electromagnetic engineering and science
• /
• v.13 no.2
• /
• pp.93-103
• /
• 2013

This paper presented a novel approach for the design of a tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprised two dual-mode single band filters using common input/output lines. Each single BPF was realized using a varactor-loaded transmission line resonator. To suppress the harmonics over a broad bandwidth, a defected ground structure was used at the input/output feeding lines. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 GHz with a 3-dB fractional bandwidth (FBW) variation from 5.76% to 8.55%, while the second passband center's frequency tunable range was 2.40 to 2.88 GHz with a 3-dB FBW variation from 8.28% to 12.42%. The measured results of the proposed filters showed a rejection level of 19 dB up to more than 10 times the highest center frequency of the first passband.