• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.9
• /
• pp.685-697
• /
• 2017

In this paper, it is presented the result of design and fabrication for C-band solid state high power amplifier unit and components using in search radar. The solid state power amplifier(SSPA) assembly was fabricated using GaN(Gallium Nitride), which is semiconductor device, and the transmit signal output power of the solid state high power amplifier unit is generated by combining the transmit signal power of the solid state power amplifier configured in parallel through a design and fabricated waveguide type transmit signal combine assembler. Designed solid state high power amplifier unit demonstrated C-band 500 MHz bandwidth, maximum 10.5% duty cycle, transmit pulse width from $0.0{\mu}s{\sim}000{\mu}s$, and transmit signal power is 44.98 kW(76.53 dBm).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.4
• /
• pp.250-254
• /
• 2016

Currently, power conversion system which converts AC to DC Power is applied in domestic urban railway. The diode rectifier is used in most of them. However the diode rectifier can not control the output voltage and can not regenerate power as well. On the other hand, PWM (pulse width modulation) converter using IGBT (isolated gate bipolar transistor) can control output voltage, allowing it to reduce the output voltage drop. Moreover the Bi-directional conduction regenerates power which does not require additional device for power regeneration control. This paper compared the simulation results for the DC power supply system on both the diode rectifier and the PWM converter. Under the same load condition, simulation circuit for each power supply system was constructed with the PSIM (performance simulation and modeling tool) software. The load condition was set according to the resistance value of the currently operating impedance of light rail line, and the line impedance was set according to the distance of each substations. The train was set using a passive resistor. PI (proportional integral) controller was applied to regulate the output voltage. PSIM simulation was conducted to verify that the PWM Converter was more efficient than the diode rectifier in DC Traction power supply system.

• The Journal of Korean Academy of Prosthodontics
• /
• v.29 no.2
• /
• pp.85-101
• /
• 1991

The purpose of this study was to determine the optimum range of laser energy density to the enamel surface of permanent incisors when they are irradiated with the pulsed Nd : YAG laser, Laser impacts on each experimental group were made at energy density of $20\sim50J/cm^2$ by 20 pulses of the pulse width 1.2 msec. The author investigated the enamel surface with the sunning electron microscope(SEM) and the surface roughness tester, and measured the shear bond strength between electrolytically etched Ni-Cr-Be alloy casting and composite resin. The obtained results were as follows: 1. The surface roughness of enamel after laser irradiation showed the significant difference level from the energy density $40J/cm^2(P<0.05)$. 2. The mean shear bond strength of etched-metal resin-bonded specimens were $154.23{\pm}33.30kg/cm^2$ at unlased enamel surface and $195.72{\pm}29.56kg/cm^2$ at lased energy density $30J/cm^2$, and showed a significant difference(P<0.05). 8. SEM photographs showed the irregular microcracks and the structural changes of lased enamel surface. 4. SEM photographs of the fracture surface after testing the shear bond strength showed the aspect of interfacial fracture between bonding agent and composite resin at the metal sides.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.54-60
• /
• 2008

The atomization characteristics of the dual air supplying twin-fluid nozzle were investigated experimentally using PIV and PDA systems. The two-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air and the main nozzle to produce the spray. The main nozzle has the swirl tip with four equally spaced tangential slots, which give the injecting fluid an angular momentum. The angle of the swirl tip varied with 0$^{\circ}$ 30$^{\circ}$, 60$^{\circ}$ and 90$^{\circ}$, and the ratios of carrier air to assist air and ALR(total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the mean velocity, turbulent intensity and SMD distributions of the sprays were measured using PDA system. As the results, the mean axial velocity at the spray centerline decrease with the increase of the swirl angle. The turbulent intensities of the axial and radial velocity were increased with the increase of the swirl angle. The mean SMD (Sauter mean diameter) of the radial direction along the axial distance shows the lowest value at the swirl angle of 60$^{\circ}$.

• Journal of Advanced Navigation Technology
• /
• v.22 no.5
• /
• pp.420-428
• /
• 2018

In this paper, represented uninterruptible power supply (UPS) equipment maintaining constant output voltage, the proposes a photovoltaic system constructed with a step up boosting chopper and single phase pulse width modulation (PWM) voltage source inverter. as power source disconnection, voltage variation and output current variation with load variation. This system is driven by being synchronized voltage fed inverter and AC source, and in the steady state of power source charge battery connected to DC side with solar cell using a Photovoltaic that it was so called constant voltage charge. It can be results of saving electric power, and through a normal operation of energy storage system (ESS), the system operated the LED a calling on signal changes at the airport in an efficient manner. In addition, better output waveform was generated because of PWM method, and it was proved to test by experiment maintained constant output voltage regardless of AC source disconnection, load variation, and voltage variation of AC power source.

• Journal of Korean Neurosurgical Society
• /
• v.37 no.2
• /
• pp.112-115
• /
• 2005

Objective: Thalamic lesioning and deep brain stimulation(DBS) have proved to be beneficial to the treatment of essential tremor(ET). The authors compared the effects and complications of two modalities. Methods: A total of 34 patients with ET were treated with ventral intermediate(Vim) nucleus thalamotomy or Vim DBS from May 1999 to May 2003. The procedure of lesioning or stimulation were performed as usual manner with or without microelectrode recording. Postoperatively, utilizing the various combinations of frequency, voltage and pulse width optimized the stimulation. The degree of improvements of tremor and the occurrence of the complications were evaluated postoperatively and at follow-up. Results: There were 38 procedures, including 27 with Vim thalamotomy and 11 with DBS, in 34 patients. Of the thalamotomy group, left Vim lesioning is 25 and right one is 2. Follow-up duration ranged from 12 to 57 months. In the thalamotomy group, the rate of overall good outcome was 88.9% but 12 patients (44.4%) showed permanent adverse effects. In the cases of stimulation, the rate of overall good outcome was 90.9% and two patients had acceptable dysarthria. Conclusion: Both Vim thalamotomy and Vim DBS were effective for the treatment of ET, although perioperative adverse effects tended to be higher in patients who had thalamotomy. In cases of DBS, adjustments of stimulation parameters enabled an acceptable position to be achieved with tremor control and unwanted effects.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2007.10a
• /
• pp.897-900
• /
• 2007

This paper presents a study on the DSP controller and IGBT inverter driver design for the power-by-wire(PBW) system using BLDC servo motor. This BLDC servo motor system was realized with DSP(Digital Signal Processor) and IGBT inveter module. The PBW system needs speed control of servo motor for linear thrust action. This paper implements a servo controller with vector control and min-max PWM technique. As CPU of controller, TMS320F2812 DSP was adopted because it has PWM(Pulse Width Modulation) waveform generator, A/D(Analog to Digital) converter, SPI( Serial Peripheral Interface) port and many input/output port etc.

• Journal of Broadcast Engineering
• /
• v.21 no.5
• /
• pp.760-769
• /
• 2016

This paper proposes a hybrid LED driving circuit and its control method for extension of the color gamut of LED. The proposed hybrid LED driving circuit provides the constant current by switching regulation in the high current and by linear regulation in the low current through LED. Furthermore, the magnitudes of the high current and low current were controlled by CC(Continuous Current) control method and PWM(Pulse Width Modulation) control method, respectively. We experimentally confirmed that the current through RGB LED is linearly controlled to 2% maximum current ratio by varying PWM in the proposed driving circuit and control method. As a result of the measurement of the output light color in CIE1976 chromaticity coordinates, we confirmed that the color, which not be expressed by the existing method, uniformly expressed. We confirmed that the color, which can not be expressed by the existing method, was uniformly output and verified that the color gamut was expanded by the low current controlled by the proposed driving circuit and control method.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.6 no.2
• /
• pp.132-140
• /
• 2001

A universal motor is a small dc series machine motor that is designed to operate from an ac machine. The characteristics of universal motors are high no-load and staring torque. Because of the high operating speed, the size of these motors for a given hp rating is typically smaller that other fractional hp ac machine, making it ideal for hand-held tools and appliances where weight, compactness, and speed are importance factors. A phase-angle control with AC drive system gains a high popularity due to their simple implementation, but contains the disadvantage of their poor input power factor, subharmonic current. Pulse width modulation control with DC drive systems increase the power factor as without delay phase angle. This paper analyzed the subharmonic characteristics of the phase angle control system that is controlled by zero voltage crossing similar to traditional method, and the dc chopper system that is used PWM.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.10
• /
• pp.4561-4568
• /
• 2011

In this paper, carrier comparison PWM method for voltage control of Vienna rectifier is discussed. In general, in industrial and communications applications, the two-level rectifier is used. However, this two-level rectifier has the limit of high THD and low efficiency. So, the studies of three-level rectifier has been carried out so far, and the Vienna rectifier circuit is the representative. The space vector pulse width modulation(SVPWM) method is generally used for Vienna rectifier, in which voltage vectors and duration time are calculated from the voltage reference. However, this method require very sophisticated and complex calculations, so realizing this method by software is very difficult. To overcome this disadvantage, simple carrier comparison PWM method for Vienna rectifier is proposed which is modified from the carrier comparison method for 3 level inverter. Furthermore, to verify the usefulness of the Vienna rectifier carrier comparison PWM the simulation and experiment are carried out.