• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

• Journal of Power Electronics
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• 제12권5호
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• pp.708-714
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• 2012

This paper presents a new interleaved pulse-width modulation (PWM) boost-flyback converter to achieve power factor correction (PFC) and regulate DC bus voltage. The adopted boost-flyback converter has a high voltage conversion ratio to overcome the limit of conventional boost or buck-boost converter with narrow turn-off period. The proposed converter has wide turn-off period compared with a conventional boost converter. Thus, the higher output voltage can be achieved in the proposed converter. The interleaved PWM can further reduce the input and output ripple currents such that the sizes of inductor and capacitor are reduced. Since boundary conduction mode (BCM) is adopted to achieve power factor correction, power switches are turned on at zero current switching (ZCS) and switching losses are reduced. The circuit configuration, principle operation, system analysis, and design consideration of the proposed converter are presented in detail. Finally, experiments conducted on a laboratory prototype rated at 500W were presented to verify the effectiveness of the converter.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권12호
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• pp.751-758
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• 2004

This paper presents a new method to compensate the non-linearity for matrix converter drives using PQR instantaneous Power theory. The non-linearity of matrix converter drives such as commutation delay, turn-on and turn-off time of switching device, and on-state switching device voltage drop is modelled by PQR power theory and compensated using a reference current control scheme. The proposed method does not need any additional hardware and off-line experimental measurements. The proposed compensation method is applied for high performance induction motor drives using a 3 kW matrix converter system without a speed sensor. Simulation and experimental results show the proposed method using PQR power theory Provides good compensating characteristic.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.413-417
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• 1998

In order to obtain better performance for a SRM(switched reluctance motor) drive, the commutation from one phase to another must be as fast as possible. In this paper a novel converter for SRM drive is proposed, which can accelerate the turn-off and turn-on time by using two capacitors to form a resonant circuit with the motor inductance. Two capacitors recover rapidly stored energy in the off going phase and establish rapidly the current rising in the on going phase. As a result, the current tail can be shortened and the dwell angle in the positive torque region can be extended. And comparing with the asymmetric converter, this converter has higher energy availability in energy conversion process and less number of switches.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.1103-1104
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• 2008

In this paper, authors propose a novel step-up AC-DC chopper operated with power factor correction (PFC) and with high efficiency. The proposed chopper behaves with discontinuous current control (DCC) of input current. The input current waveform in the proposed chopper is got to be a discontinuous sinusoid form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC chopper, the switching devices are turned-on with the zero current switching, but turn-off of the switching devices is switched at current maximum value. To achieve a soft switching of the switching turn-off, the proposed chopper is used a new partial resonant circuit. The result is that the switching loss is very low and the efficiency of chopper is high.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2326-2333
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• 2015

Stator turn faults in permanent magnet synchronous motors (PMSMs) are more dangerous than those in induction motors (IMs) because of the presence of spinning rotor magnets that can be turned off at will. Condition monitoring and fault detection and diagnosis of the PMSM have been receiving a growing amount of attention among scientists and engineers in the past few years. The aim of this study is to propose a new detection technique of stator winding faults in a three-phase PMSM. This technique is based on the image analysis and recognition of the stator current Concordia patterns, and will allow the identification of turn faults in the stator winding as well as its correspondent fault index severity. A test bench of a vector controlled PMSM motor behaviors under short circuited turn in two phases stator windings has been built. Some experimental results of the phase to phase short circuits have been performed for diagnosis purpose.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.596-599
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• 1991

This paper describes a novel switching algorithm of series connected power semiconductors for high voltage applications. In order to improve the reliability and efficiency of high voltage static power converters, we study on the switching characteristics of series connected power semiconductors and then propose "a servo control of snubber capacitor value" for the dynamic voltage balancing under turn-off state in series connected power semiconductors. Finally, we illustrate the validity of this algorithm by computer simulation and experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.759-762
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• 2002

A ZCT(Zero Current Transition) PWM(Pulse-Width-Modulation) boost converter using parallel MOSFET switch is proposed in this paper. The IGBT(main switch) of the proposed converter is always turned on with zero current switching and turned off with zero current/zero voltage switching. The MOSFET(auxiliary switch) is also operates with soft switching condition. In addtion to, the proposed converter eliminates the reverse recovery current of the freewheeling diode by adding the resonant inductor, Lr, in series with the main switch. Therefore, the turn on/turn off switching losses of switches are minimized and the conduction losses by using IGBT switch are reduced. In addition to, using parallel MOSFET switch overcomes the switching frequency limitation occurred by current tail. As mentioned above, the characteristics are verified through experimental results.

• 대한안전경영과학회지
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• 제16권2호
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• pp.167-174
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• 2014

Heating and air conditioning system is changing rapidly from the traditional HVAC central supply system to the individual supply system with electrical heat pump system (EHP) in Korean school buildings. The individual supply system has advantages to turn on and off individually and to adjust the thermal comfort separately, but energy is wasted in the unoccupied classroom when the last leaving occupant does not turn off the controller. If the controller is to be off automatically while the classroom is not in use, energy consumption would decrease dramatically. This project aims to cease the unnecessary EHP supply in vacant classroom by inputting the class schedule from the central control room to reduce the energy-spending. Experimental measurements were carried out between the controlled classroom that is turned off when not in use and the uncontrolled room that is turned on continually. Occupant's comfort and energy consumption were measured and compared between the controlled case and the uncontrolled case. The energy consumption of controlled classroom case is 30-60% less than that of the uncontrolled classroom case. This result shows that controlling the cooling supply for the unoccupied classroom using the class schedule can decrease the energy consumption remarkably. This supply control system can be used to conserve energy in school structures like universities.

• Physical Therapy Rehabilitation Science
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• 제7권2호
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• pp.54-60
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• 2018

Objective: Persons with chronic stroke fall more often than healthy elderly individuals. The Timed Up and Go test (TUG) is used as a fall prediction tool, but only provides a result for the total measurement time. This study aimed to determine the optimal cut-off values for each of the 6 components of the TUG. Design: Retrospective study. Methods: Thirty persons with chronic stroke participated in the study. TUG evaluation was performed using a wearable miniaturized inertial sensor. Sensitivity, specificity, and predictive values were calculated using the Receiver Operating Characteristic (ROC) curve analysis for the measured values in each section. Optimal values for fall risk classification were determined. Logistic regression analysis was used to investigate the risk of future falls based on TUG. Results: The cut-off values of the 6 sections of the TUG were determined, as follows: sit-to-stand >2.00 seconds (p<0.05), forward gait >4.68 seconds (p<0.05), mid-turn >3.82 seconds (p<0.05), return gait >4.81 seconds (p<0.05), end-turn >2.95 seconds (p<0.05), and stand-to-sit >2.13 seconds (p<0.05). The risk of falling increased by 2.278 times when the mid-turn value was >3.82 seconds (p<0.05). Conclusions: The risk of falls increased by 2.28 times when the value of the mid-turn interval exceeded 3.82 seconds. Therefore, when interpreting TUG results, the predictive accuracy for falls will be higher when the measurement time for each section is analyzed, together with the total time for TUG.