• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.403-405
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• 1988

Recently, Power change devices using thyristor and transistor have grown with the rapid development of power electronics. But the devices using these semiconductors generate harmonics from the non-linear load, which gives rise to various obstacles. In this paper, therefore, as 3 taps are connected in input line, we can multiply the pulse in input line, by which harmonics is reduced.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.5
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• pp.10-14
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• 1981

This paper deals with design of circuit that gives a linear relationship between the voltage controlling the Phase delay an인e of thrysistor trigger pulse and the average voltage in the load. The design is based an the method of linear triggering of thrysistion. It is shown that method is also effective with the input signal how variable frequencies.

• Structural Engineering and Mechanics
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• v.3 no.6
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• pp.583-592
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• 1995

The concept of "Saturation Impulse" for rigid, perfectly plastic structures with finite-deflections subjected to dynamic loading was put forward by Zhao, Yu and Fang (1994a). This paper extends the concept of Saturation Impulse to the analysis of structures such as simply supported circular plates, simply supported and fully clamped square plates, and cylindrical shells subjected to rectangular pressure pulses in the medium load range. Both upper and lower bounds of nondimensional saturation impulses are presented.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.298-299
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• 2020

Triple Active Bridge 컨버터의 경부하 조건에서의 효율 개선을 위해 브리지의 듀티와 위상을 동시에 변경하는 Dual Pulse Width Modulation(DPWM)기법을 적용하였다. 기존의 위상천이기법은 제어가 단순한 장점이 있으나 경부하 조건에서 효율이 급격히 감소하는 단점이 존재한다. 따라서 본 논문에서는 DPWM 방식을 통해 경부하 조건의 효율 개선을 위한 각 브리지 듀티, 위상각을 분석하였고, 시뮬레이션을 통해 이를 검증하였다.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.482-491
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• 2001

An experimental study has been carried out to investigate an I-type sparger-performance in view of pressure oscillation and thermal mixing in a pool. Its pitch-to-hole diameter, P/D, varies from 2 to 5. The test conditions are restricted to the condensation oscillation regime. In the present study, two different hole patterns, staggered and parallel types, are employed under various test conditions. The amplitude of the pressure pulse shows a peak for pool temperatures of 45∼85$\^{C}$, which depends on P/D and the steam mass flux. The effect of hole pattern on the pressure load is smaller than that of P/D. The dominant frequency increases with the subcooling temperature of pool water and P/D. A correlation for the dominant frequency is proposed in terms of the pitch-to-hole diameter ratio and other dimensionless thermal hydraulic parameters.

• Journal of Power Electronics
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• v.15 no.3
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• pp.702-711
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• 2015

In this paper, an effective carrier-based modulation (CBM) strategy to reduce the switching losses for indirect matrix converters (IMCs) is presented. The discontinuous pulse width modulation method is applied to decrease the switching numbers in one carrier cycle, and an optimum offset voltage is selected to avoid commutations of the high output phase currents. By decreasing the switching numbers along with avoiding commutation of the high currents, the proposed CBM strategy significantly reduces the switching losses in IMCs. In addition, the proposed CBM strategy is independent of load conditions, such as load power and power factor, and it has good performance in terms of the input/output waveforms. Simulation and experimental results are provided to verify the effectiveness of the proposed CBM strategy.

• ETRI Journal
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• v.38 no.4
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• pp.645-653
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• 2016

This paper demonstrates the performance of a metal-substrate power module with multiple fabricated chips for a high current electrical application, and evaluates the proposed module using a 1.5-kW sinusoidal brushless direct current (BLDC) motor. Specifically, the power module has a hybrid structure employing a single-layer heat-sink extensible metal board (Al board). A fabricated motor driver IC and trench gate DMOSFET (TDMOSFET) are implemented on the Al board, and the proper heat-sink size was designed under the operating conditions. The fabricated motor driver IC mainly operates as a speed controller under various load conditions, and as a multi-phase gate driver using an N-ch silicon MOSFET high-side drive scheme. A fabricated power TDMOSFET is also included in the fabricated power module for three-phase inverter operation. Using this proposed module, a BLDC motor is operated and evaluated under various pulse load tests, and our module is compared with a commercial MOSFET module in terms of the system efficiency and input current.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.309-313
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• 1990

Pulse width modulation using discontinuous conduction modes are applied to a full-bridge series resonant converter to regulate the output from no load to full load with low switching loss and a narrow range of frequency variation. Finally, a simple nonlinear discrete-time dynamic model for this proposed converter is derived using approximation. This discrete time model is linearized and a general input - output transfer function for the propelled converter is derived.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1104-1107
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• 1992

Voltage controlled current regulated PWM(pulse width modulation) of VSI (voltage source inverter) is proposed. Adopting one degree of freedom, the voltage, the current controller shows much more improvement than conventional ones not using this method. The voltage controller or this proposal needs load's parameters, torque value, rotational speed. This voltage controller is located at converter part which links AC source and DC bus. With this proposed method, duty ratio of the inverter's switching is nearly unity for all speed and torque range. Hence, this method gets many advantages such as reducing current ripple, thermal loss, and noises and improving control performances. Theoretical approach to this voltage-current controller is performed, and the results are presented.

• Structural Engineering and Mechanics
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• v.37 no.5
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• pp.509-527
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• 2011

The paper investigates the dynamic buckling behaviour of a laminated composite stiffened cylindrical shell using the commercial finite element code ABAQUS. The numerical model of the composite shell is validated by static tests. In particular, the experimental collapse test is numerically simulated by a quasi static analysis carried out by both ABAQUS/Standard and ABAQUS/Explicit. The behaviour in the post-buckling field and the collapse load obtained by the analyses are close to the experimental data. The validated model is then used to study the dynamic buckling behaviour with ABAQUS/Explicit. The effects of the loading magnitude and of the loading duration are investigated, implementing in the analysis also first-ply failure criteria. It is observed that the dynamic buckling load is highly affected by the loading duration.