• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.8
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• pp.883-890
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• 2015

As the semiconductor processing technology has been developing, multiple cores or NoC(network on chip) can be contained in recent chips. GALS(globally asychronous locally synchronous) clocking scheme that has multi-clock domains with different frequencies or phase differences is widely used to solve power consumption and clock skew in a large chip with a single clock. A synchronizer is needed to avoid a synchronization problem between sender and receiver in GALS. In this paper, the setup and hold time of DFF required to design the synchronizer are measured using 180nm CMOS processing parameters depending on temperature, supply voltage, and the size of inverter in DFF. The simulation results based on the bisection method in HSPICE show that the setup and hold time are proportional to temperature, however they are inversely proportional to supply voltage, and negative values are measured for the hold time.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.2
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• pp.97-103
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• 2006

This paper designs mono block type with rotating high power radiography x-ray generator and studies 16kW X-ray generator possible to adapt hospital mobile radiography and industrial X-ray equipment and design. This equipment uses rotating anode type x-ray tube at high voltage generator to generate x-ray and adds rotor operating circuit to operate rotor of x-ray tube. The size of high voltage transformer and high voltage generator is minimized by high voltage high frequency inverter has 100kHz switching frequency. Also this paper shows result of x-ray tube voltage and tube current correspond to variable load.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.538-545
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• 2001

In this paper a gearless drive system using a permanent-maget synchronous motor for high speed elevators is addressed. The application of permanent magnet synchronous motor to an elevator traction machine enables several improvements including higher efficiency better ride comfort smaller size and lighter weight and so on A PWM boost converter has been also adopted so that DC-link voltage regulation bi-directional power flow and controllable power factor with reduced input current harmonics are possible. To increase the reliability and performance of overall control system the unified control board which can include the car and group controller as well as PWN converter/inverter controller has been designed based on a DSP TMS320VV33. In addition the dynamic load simulator system has been developed so that the drive system of high speed elevator can be tested and evaluated without and limitation on ride distance. Some experimental results are given to verify the effectiveness of the developed system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.2
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• pp.109-117
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• 2005

In this study, the 1/20 reduced-scale experiments using Froude scaling were conducted to investigate the ventilation velocity of the variation of burning rate in tunnel fires. The heptane square pool fire with heat release rate ranging from 3.71~15.6 kW were used. The burning rate of fuel was obtained by measuring mass using load cell and temperature distributions were measured by K-type theomocouples in order to investigate smoke movement. The ventilation velocity in the tested tunnel was controlled by inverter of the wind tunnel. In heptane pool fire case, the increase in ventilation velocity incresed the burning rate due to the direct supply of oxygen to the fire plume. For the same dimensionless velocity($\bar{V}$), burning rate increased as the size of pool fire decreased.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1462-1469
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• 2008

This paper proposes the design method based on the Composite Right/Left-Handed(CRLH) structure to miniaturize and enhance the rejection performance in the stopband of the bandpass filter for a VHF band($169{\sim}211\;MHz$). For realization, we used the 0-th order resonance point of the CRLH and the simple theory of Inverter as coupling. The proposed technique is validated by the performance predictions and experiments, (Insertion loss <2 dB, $S_{11}$< -15 dB, suppression of up to the 3rd harmonic) and it is found out that the suggested method enables the size reduction of around 60 % from the conventional filters such as the parallel edge coupled type.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.22-28
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• 2003

This paper describes the frequency dependence of the grounding impedance. In order to propose the evaluation method of the transient response of powered grounding systems, the grounding impedances were measured with varying the frequency of incoming currents by way of the variable frequency inverter and band pass filter. The magnitude and phase of the grounding impedance were analyzed in the frequency range of 20 [Hz]∼2.1[kHz]. The grounding impedance were increased with increasing the frequency of the test current. The grounding impedance at the frequency of 2[kHz] in the actual 22.9[kV] substation grounding system was approximately 3 times as large as the 60[Hz] grounding impedance. It was found that the frequency dependence of the grounding impedance is mainly subject to the inductive reactance of the grounding conductors. As a result, it is critical to determine the shape and size of grounding grid reducing the resultant inductance in grounding systems for lightning surge protection.

• Architectural research
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• v.17 no.3
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• pp.109-115
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• 2015

The dynamic pricing of electricity, where the electricity rate increases in a time zone with a high demand for electricity is typically applied to a building whose power reception capacity is greater than a certain size. This includes the time of use(TOU) electricity pricing in Korea which can induce the effect of reducing the power demand of a building. Meanwhile, a VRF (Variable Refrigerant Flow) system that uses electricity is regarded as one of the typical heating and cooling systems along with central air conditioning (central HVAC) for its easy operation and application to the building. Thus, to reduce power energy and operating costs of a building in which the TOU and VRF systems are applied simultaneously, we suggested a control for changing the indoor temperature setting within the thermal comfort range or limiting the rotational speed of an inverter compressor. In this study, to describe the features of the above-mentioned control and verify its effects, we evaluated the results obtained from the analysis of its operation data. Through the actual measurements in winter operations for 73 days since mid- December 2014, we confirmed a reduction of 10.9% in power energy consumption and 12.2% in operating costs by the new control. Also, a reduction of 13.3% in power energy consumption was identified through a regression analysis.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.8
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• pp.46-51
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• 2002

A new interleaved synchronous mirror delay(SMD) is proposed in order to reduce the circuit size and the power. The conventional interleaved SMD has multiple pairs of forward delay array(FDA) and backward delay away(BDA) in order to reduce the jitter. The proposed interleaved SMD. requires one FDA and one BDA by changing the position of multiplexer. Moreover, the proposed interleaved SMD solves the polarity problem with just one extra inverter. Simulation results show that about 30% power reduction and 40% area reduction are achieved in the proposed interleaved SMD. All circuit simulations and implementations are based on a 0.25um two-metal CMOS technology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.2
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• pp.212-215
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• 2016

In this paper, a 5.08 GHz Ring Voltage Controlled Oscillator(Ring VCO) was implemented using $0.18{\mu}m$ standard CMOS technology. The proposal Ring VCO is 3-stage structure. This research confirmed that the each stage's different transistor size ratio influence the current change and alter power consumption consequentially. This circuit is formed to control the current thereby adding the Current Mirror and to tune the frequency by supplying control voltage. It has an 65.5 %(1.88~5.45 GHz) tuning range. The measured output power is -0.30 dBm. The phase noise is -87.50 dBc/Hz @1 MHz offset with operating frequency of 5.08 GHz fundamental frequency. The total power consumption of Ring VCO is 31.2 mW with 2.4 V supply voltage.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.2
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• pp.94-100
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• 2005

Korea Electrotechnology Research Institute(KERI) has successfully developed a 100hp-1800rpm-class high temperature superconducting(HTS) motor with high efficiency under partnership with Doosan Heavy Industries & Construction Co. Ltd. This motor has a HTS field winding and an air-cooled stator. The advantages of HTS motor can be represented by a reduction of 50% in both losses and size compared to conventional motors of the same rating. The cooling system is based on the heat transfer mechanism of the thermosyphon by using GM cryocooler as cooling source. The cold head is in contact with the condenser of a Ne-filled thermosyphon. Independently, the rotor assembly was tested at the stationary state and combined with stator. The HTS field winding could be cooled into below 30K. Test of open-circuit characteristics(OCC) and short-circuit characteristics(SCC) and load test with resistive load bank were conducted in generator mode. Also, load tests in motor mode driven by inverter were finished at KERI. Maximum operating current of field winding at 30K was 120A. From OCC and SCC test results synchronous inductance and synchronous reactance were 2.4mH, 0.49pu, respectively. Efficiency of this HTS machine was 93.3% in full load(100hp) test. This paper will present design, construction. and experimental test results of the 100hp HTS machine.