• Progress in Superconductivity and Cryogenics
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• v.21 no.1
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• pp.25-30
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• 2019

This paper presents a conceptual design approach of air-cored synchronous machine with high temperature superconductor (HTS) field winding. With a given configuration of a target machine, boundary conditions are set in the cylindrical coordinate system and analytic field calculation is performed by solving a governing equation. To set proper boundary conditions, current distributions of the field winding and the armature winding are expressed by the Fourier expansion. Based on analytic magnetic field calculation results, key machine parameters are calculated: 1) inductance, 2) critical current of field winding, 3) weight, 4) HTS conductor consumption, and 5) efficiency. To investigate all potential design options, 6 sweeping parameters are determined to characterize the geometry of the machine and the parameter calculation process is performed for each design options. Among design options satisfying constraints including >80 % critical current margin and >95 % efficiency, in this paper, a first-cut design was selected in terms of overall machine weight and HTS conductor consumption to obtain a lightweight and economical design. The goal is to design a 5-MW machine by referring to the same capacity machine that was previously constructed by another group. Our design output is compared with finite element method (FEM) simulation to validate our design approach.

• 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.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.325-333
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• 2021

A 3 kW grid-tied PV inverter with Gallium nitride high-electron mobility transistor (GaN HEMT) for domestic commercialization was developed using boost converter and full-bridge inverter with LCL filter topology. Recently, many GaN HEMTs are manufactured as surface mount packages because of their lower parasitic inductance characteristic than standard TO (transistor outline) packages. A surface mount packaged GaN HEMT releases heat through either top or bottom cooling method. IGOT60R070D1 is selected as a key power semiconductor because it has a top cooling method and fairly low thermal resistances from junction to ambient. Its characteristics allow the design of a 3 kW inverter without forced convection, thereby providing great advantages in terms of easy maintenance and high reliability. 1EDF5673K is selected as a gate driver because its driving current and negative voltage output characteristics are highly optimized for IGOT60R070D1. An LCL filter with passive damping resistor is applied to attenuate the switching frequency harmonics to the grid-tied operation. The designed LCL filter parameters are validated with PSIM simulation. A prototype of 3 kW PV inverter with GaN HEMT is constructed to verify the performance of the power conversion system. It achieved high power density of 614 W/L and peak power efficiency of 99% for the boost converter and inverter.

• Journal of Korean Society of Transportation
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• v.23 no.5 s.83
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• pp.123-134
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• 2005

This research aims at developing a new method which can replace the existing method. known as the quality factor(Q factor) method by an L-R-C test for use in the performance test of inductive loop detectors(ILD) being installed and maintained. In this study, a sensor to detect a magnetic field in terms of frequency and intensity, a method to collect field data, the method of analysis, and the method of diagnosis were developed. An automatic diagnosis system which was developed to overcome those drawbacks has the following features : First, field data is collected automatically by a test vehicle equipped with magnetic field sensors that is running can be said to along the roadway and. thus, the new system completely overcome the roadway and, thus, the new system can be said to completely overcome the inefficiency of the existing method second, since the magnetic fold generated from the ILD is the final output of the whole system of ILD, the existing problem has been solved. third. since each of the detection area by height is collected by the magnetic sensors installed by height. a basic for the identification of the vehicle types to be detectable and the setting of adjustment factors has been made. For the automatic diagnosis system developed during in this study, a reliability test was carried out by comparing vehicle times of ILD installed ideally.