• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.231-239
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• 1998

This paper presents the dynamic analysis and control loop design of a zero voltage switching full bridge (ZVS-FB) PWM DC/DC converter. The small-signal model is derived incorporating the effects of phase shift control and the utilization of transformer leakage inductance and power FET junction capacitance to achieve zero voltage resonant switching. These effects are modeled by introducing additional feedforward and feedback terms for duty cycle modulation. Based on the results of the small-signal analysis, the control loop is designed using a simple two-pole one-zero compensation circuit. To show the validity of the design procedures, the small signal analysis of the closed loop system is carried out and the potential of the zero voltage switching and the superiority of the dynamic characteristics are verified through the experiment with a 2 kW prototype converter.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.39-42
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• 1996

This paper proposes a novel Auxiliary Resonant Commutated Pole Inverter (ARCPI) topology. The conventional ARCPIs make the hard switching at turn-off likewise the conventional PWM inverters. Therefore, turn-off switching losses may be so serious and can be so much considerable in high power level. The proposed ARCPI can solve this problem with high frequency transformers, switches, and capacitors. All the switches in the expanded auxiliary circuit achieves the soft switching and operates only during the commutating intervals. The characteristics and the analysis for each operation mode are described in detail and the validity is verified by the simulations and the experimental results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.4
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• pp.571-577
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• 1986

In this paper, we have investigated pole-zero shifting due to variable stopband frequency Ws and passband ripple Ap of elliptic function filters. Also we have studied the phase, group-delay, unit step response and impulse response of elliptic filters. We show that in the passband the phase linearity improves as Ws increases, and eventually it approaches that of a chebyshev function filter.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.324-328
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• 2001

This paper presents parallel operation and control loop design of ZVT(Zero Voltage Transition) Full Bridge DC/DC Converter. At parallel operation of ZVT Full Bridge Converter, dynamic current shared inductor devides the same current of unit converter and ZVT circuit and aids to high efficiency in the system. Base on the modeling of ZVT. Full Bridge Converter, the control loop is designed using a simple two-pole, one-zero compensation circuit. To show the validity of the design procedures, the small signal analysis of the closed loop system and open loop system is carried out and the superiority of the dynamic characteristics is verified through the experiment with a 2kW, 50kHz prototype converter.

• Journal of Power Electronics
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• v.14 no.3
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• pp.444-457
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• 2014

This paper presents the design and realization of a digital PV simulator with a Push-Pull Forward (PPF) circuit based on the principle of modular hardware and configurable software. A PPF circuit is chosen as the main circuit to restrain the magnetic biasing of the core for a DC-DC converter and to reduce the spike of the turn-off voltage across every switch. Control and I/O interface based on a personal computer (PC) and multifunction data acquisition card, can conveniently achieve the data acquisition and configuration of the control algorithm and interface due to the abundant software resources of computers. In addition, the control program developed in Matlab/Simulink can conveniently construct and adjust both the models and parameters. It can also run in real-time under the external mode of Simulink by loading the modules of the Real-Time Windows Target. The mathematic models of the Push-Pull Forward circuit and the digital PV simulator are established in this paper by the state-space averaging method. The pole-zero cancellation technique is employed and then its controller parameters are systematically designed based on the performance analysis of the root loci of the closed current loop with $k_i$ and $R_L$ as variables. A fuzzy PI controller based on the Takagi-Sugeno fuzzy model is applied to regulate the controller parameters self-adaptively according to the change of $R_L$ and the operating point of the PV simulator to match the controller parameters with $R_L$. The stationary and dynamic performances of the PV simulator are tested by experiments, and the experimental results show that the PV simulator has the merits of a wide effective working range, high steady-state accuracy and good dynamic performances.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.874-877
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• 2004

This paper presents the bus controller analysis of a power control unit of GEO satellite with 3kW power output. The sensing error of bus voltage produce control signal of the shunt switch assembly and the battery power converter, and the tolerance of error signal generated decide the stability of proposed system. The worst case analysis considered for the initial tolerance, temperature effect, tolerance of end of life is peformed to verify a designed bus controller. And also, the stability of system proposed according to moving of zero and pole values by some component failures is analyzed.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.848-853
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• 2001

A study about the shrink fits of rotor and retaining ring in generator was performed for the cases of three radial interference. The shrink-fitted retaining ring used to restrain the end turns of the winded coils in the rotor against centrifugal force requires very careful attention during design and manufacture because it has traditionally been the highest-stressed component of the generator. The contact pressures and residual stresses were obtained by the finite element analysis for each radial interference at zero, 100% rated, and 120% rated speeds, respectively. The results of analysis show that the radial interference in use needs to be increased carefully.

• Journal of Magnetics
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• v.18 no.2
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• pp.117-124
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• 2013

Single-phase, brushless DC (BLDC) motors have unequal air-gaps to eliminate the dead-point where the developed torque is zero. Unfortunately, these unequal air-gaps can deteriorate the motor characteristics in the cogging torque. This paper proposes a novel design for a single-phase BLDC motor with an asymmetric notch to solve this problem. In the design method, the asymmetric notches were placed on the stator pole face, which affects the change in permanent magnet shape or the residual flux density of the permanent magnet. Parametric analysis was performed to determine the optimal size and position of the asymmetric notch to reduce the cogging torque. Finite element analysis (FEA) was used to calculate the cogging torque. A more than 28% lower cogging torque compared to the initial model with no notch was achieved.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1065-1067
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• 2000

This paper describes performance analysis of ARCP Inverter, which can offer zero voltage switching at nominal voltage stress. The system consists of a voltage-source inverter with sort-switching module. Each main switch is connected in parallel with resonant capacitor and two auxiliary switches are placed in series with a resonant reactor for soft-switching capability. The described ARCP inverter could be effectively applied for active power filter reactive power compensator, and UPS.

• Steel and Composite Structures
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• v.36 no.2
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• pp.229-247
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• 2020

This study analyzed stresses in concrete and its reinforcement, computing the additional loading transferred by concrete creep. The loading varied from zero, structure exclusively under its self-weight, up to the critical buckling load. The studied structure was a real, tapered, reinforced concrete pole. As concrete is a composite material, homogenizing techniques were used in the calculations. Due to the static indetermination for determining the normal forces acting on concrete and reinforcement, equations that considered the balance of forces and compatibility of displacement on cross-sections were employed. In the mathematical solution used to define the critical buckling load, all the elements of the structural dynamics present in the system were considered, including the column self-weight. The structural imperfections were linearized using the geometric stiffness, the proprieties of the concrete were considered according to the guidelines of the American Concrete Institute (ACI 209R), and the ground was modeled as a set of distributed springs along the foundation length. Critical buckling loads were computed at different time intervals after the structure was loaded. Finite element method results were also obtained for comparison. For an interval of 5000 days, the modulus of elasticity and critical buckling load reduced by 36% and 27%, respectively, compared to an interval of zero days. During this time interval, stress on the reinforcement steel reached within 5% of the steel yield strength. The computed strains in that interval stayed below the normative limit.