• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.313-319
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• 2019

Induction motors connected with a three-phase AC system may malfunction due to reverse phase or open phase faults. Conventional overcurrent relays and overheating relays are used to prevent such accidents; however, their drawbacks include a low response speed and false operation. Therefore, in this study, a digital relay for the reverse-open phase was designed and fabricated. This relay can detect the reverse phase and open phase faults and send a trigger signal to the control circuit. The proposed relay was developed based on a microcontroller. The detection times of the reverse phase and open phase were verified as 320ms and 80ms, respectively. Compared with conventional relays that only protect the motor from one type of fault, the proposed relay can detect both, reverse phase and open phase faults. In addition, the fault detection, identification criterion, and trigger signal patterns can be modified by programming according to the requirements of users.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.255-258
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• 2012

In this paper, with a thermoelectric device using the seebeck effect which generates electromotive force by temperature difference generates electric energy an energy harvesting circuit using MPPT(Maximun Power Point Traking) control is designed. After periodically sampling the open voltage of the thermoelectric device, the 1/2 voltage of open voltage which in a maximum power point is maintained through MPPT control circuit and harvested energy from thermoelectric device is delivered to load through a switch. The proposed thermal energy harvesting circuit is designed with $0.35{\mu}m$ CMOS process and the chip area excluding pads is $1168.7{\mu}m{\times}541.3{\mu}m$.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1950-1963
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• 2016

A novel open-circuit fault diagnosis method for 3-phase 4-wire 3-level active power filters based on voltage error correlation is proposed in this paper. This method is based on observing the output pole voltage error of the active power filter through two kinds of algorithms. One algorithm is a voltage error analytical algorithm, which derives four output voltage error analytic expressions through the pulse state, current value and dc bus voltage, respectively, assuming that all of the IGBTs of a certain phase come to an OC fault. The other algorithm is a current circuit equation algorithm, which calculates the real-time output voltage error through basic circuit theory. A correlation is introduced to measure the similarity of the output voltage errors between the two algorithms, and OC faults are located by the maximum of the correlations. A FPGA has been chosen to implement the proposed method due to its fast prototyping. Simulation and experimental results are presented to show the performance of the proposed OC fault diagnosis method.

• 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.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.102-106
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• 2009

This paper presents the design and optimization of output matching network according to envelope for class F power amplifier(PA) which is to apply to envelope elimination and restoration(EER) transmitter. In this paper, to increase the PAE of class F power amplifier which applies to EER transmitter, the varactor diode has been used on output matching network. As envelope changes, it optimizes constitution of harmonic trap that is short circuit in 2nd-harmonic and is open circuit in 3rd-harmonic. When drain voltage changes from 25 V to 30 V, some percentage is improved in the PAE.put the abstract of paper here.

• Journal of the Korean Institute of Telematics and Electronics
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• v.4 no.4
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• pp.13-18
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• 1967

Since all the poles of the open circuit voltage transfer function of the trigonometric, linear, passive RC circuits exist on the negative real axis of s-plane, its transient response to the unit step input is monotonic. This satisfies the necessary conditions for the applicability of Elmore's method which had been developed originally for the transient analysis of lumped circuit in computing the rise time and delay time of the trigonometric distributed RC circuits. This paper describes the computing method of rise and delay times of the trigonometric distributed RC circuit. The analysis shows that the transient response of this kind circuit depends only upon the time constant and distance angle $\theta$. As $\theta$ is increased, the rise and delay titles are increased non-linearly.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.82-88
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• 2001

Manufactured easy elevator can drives from the first floor to fifth floor as sequence control circuit in cause opening than existing equipment of experiment and practice, the structure of in the first implementation process are hand-worked control component with push-button, L/S and relay, it is structured a lamp to express that the door open and moving of cage by mechanical action of For/Rev motor-braker of which load. The second structure of implement process to control from the first floor to the fifth floor with the PLC elevator program can control by the sensor of hand-operated function of L/Sl~L/S5 in time that the S/Wl~S/W5 of PLC control panel operates to the For/Rev. The function of two kind process that an elevator is driven by PLC program and the sequence control relay circuit is a mechanical relay sequence control field and it is equipment apparatus of it to get appropriately the technology of For/Rev in that mechanical operating cause of a load using the PLC program. Also the wring circuit using a plug, dissembly. the circuit and the principle of component, and PLC program with the function test can be used the implementation field to the total technology theory about FA.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1107-1112
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• 2002

An easy elevator originated is an opened system to compare an existing equipment, and learning efficient is high as a wiring that the sequence control circuit is on and off. The structure of an equipment to be controled from the first floor to the fifth floor is constructed by a lamp to express the function of the open-close of the door according to the cage moving, to express the mechanical actuation of the forward-reverse break and motor of load and of hand-worked control component of Push-Button S/W, L/S and Relay. In order to act of the elevator function that these components connected, designed the auto program and the sequence control circuit. Consequently the process that these(1~5steps) operated the cage with an auto program of the elevator and the sequence control circuit is controled by the step of forward and reverse that the L/S1~L/S5 of sensor adjust function let posit, by the adjustable S/W1~S/W5 of PLC testing panel and the S/W1~S/W5 which installed on the transparent acryl plate of a frame. In here, improved apparatus is the learning equipment of combined use to study the principle and the technique of the originated sequence control circuit and the auto program of PLC.

• Korean Journal of Materials Research
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• v.24 no.4
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• pp.186-193
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• 2014

A thin Cu seed layer for electroplating has been employed for decades in the miniaturization and integration of printed circuit board (PCB), however many problems are still caused by the thin Cu seed layer, e.g., open circuit faults in PCB, dimple defects, low conductivity, and etc. Here, we studied the effect of heat treatment of the thin Cu seed layer on the deposition rate of electroplated Cu. We investigated the heat-treatment effect on the crystallite size, morphology, electrical properties, and electrodeposition thickness by X-ray diffraction (XRD), atomic force microscope (AFM), four point probe (FPP), and scanning electron microscope (SEM) measurements, respectively. The results showed that post heat treatment of the thin Cu seed layer could improve surface roughness as well as electrical conductivity. Moreover, the deposition rate of electroplated Cu was improved about 148% by heat treatment of the Cu seed layer, indicating that the enhanced electrical conductivity and surface roughness accelerated the formation of Cu nuclei during electroplating. We also confirmed that the electrodeposition rate in the via filling process was also accelerated by heat-treating the Cu seed layer.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.723-726
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• 2002

In this paper, a high efficiency leakage transformer for neon tube is developed to improve its power factor, to reduce its core loss and weight by using a technique of shape optimization and direction of grain-oriented silicon steel sheet. A protection circuit is designed for all types of neon transformer loaded with one or more neon lamps. Whenever the neon tube fails to be started up or comes to the life end, or encounters faults with open-circuits at the output terminals of the neon transformer, the protection circuit will be initiated to avoid more critical hazards. These neon transformers need a protection circuit to prevent from current stresses on circuit components by neon tube fail. The input of the transformer is automatically cut off when the abnormal condition occurs, preventing waste of no-load power. As the results of the study, the core weight is reduced by $11\%$, the power factor improved by $5\%$ and the efficiency increased by $6\%$ compared with the conventional type due to the employment of the grain-oriented steel sl)eel and the optimized core shape.