• Journal of electromagnetic engineering and science
• /
• 제18권1호
• /
• pp.41-45
• /
• 2018

In this study, a short-ended coupled line with a short-circuit stub transmission line bandpass filtering impedance transformer is presented. The general designed equations are derived on the basis of circuit theory. The design curves are provided to examine the characteristic of the proposed impedance transformer. The proposed circuit is suitable for high termination impedance. To validate the design formulas, a $400-50{\Omega}$ impedance transformer is designed and fabricated at the operating center frequency ($f_0$) of 2.6 GHz. The measured results show a good agreement with the simulation. The measured insertion and return losses are 0.6 dB and 22.5 dB at $f_0$, respectively. The measured return loss is higher than 20 dB within the passband frequency of 2.51-2.7 GHz. Moreover, the stopband attenuation is higher than 25 dB from DC to 1.64 GHz of the lower stopband and from 3.12 GHz to 6.4 GHz of the higher stopband.

• Journal of Electrical Engineering and Technology
• /
• 제11권3호
• /
• pp.675-682
• /
• 2016

Sudden voltage drops and outages frequently disturb the operation of sensitive loads for domestic, commercial, and industrial use. In some cases, these events may even impair the functioning of relevant equipment. To maintain power under such conditions, a UPS system is usually installed. Once a disturbance happens at the grid side, the line-interactive UPS system takes over the load to prevent an interruption. But, due to magnetic saturation of the transformer, a significant inrush current may occur for the transformer-coupled loads during this transition. The generation of such transient currents may in turn decrease the line voltage and activates over-current protecting devices of the system. In this work, a cost-effective, line-interactive UPS system is proposed that eliminates the inrush current phenomenon associated with transformer-coupled loads. The strategy was implemented by connecting a standard current-regulated voltage source inverter (CRVSI) to the secondary winding of the load transformer. During any transient condition at the grid side, the load current is monitored and regulated to achieve either seamless compensation of the load current or complete transferal of load from grid to the inverter. Experimental results were obtained for a prototype under all possible operating conditions so as to validate the performance of the proposed topology.

• Journal of Electrical Engineering and Technology
• /
• 제10권1호
• /
• pp.288-294
• /
• 2015

Recently, the module-integrated converter has shown an interest in the photovoltaic generation system. In this system, the high frequency transformer should be compact and efficient. The proposed method is based on the correlation characteristic between the copper and core loss to minimize the loss of transformer. By sizing an effective cross-sectional area and window area of core, the amount of loss is minimized. This paper presents the design and analysis of high frequency transformer by using the 3D finite element model coupled with DC-DC converter circuit for more accurate analysis by considering the nonlinear voltage and current waveforms in converter circuit. The current waveform in each winding is realized by using the ideal DC voltage source and switching component. And, the thermal analysis is performed to satisfy the electrical and thermal design criteria.

• Journal of electromagnetic engineering and science
• /
• 제16권1호
• /
• pp.13-18
• /
• 2016

This paper presents a design of an impedance transformer (IT) with high frequency selectivity characteristics. The frequency selectivity can be controlled by even- and odd-mode impedance of a shunt coupled transmission line (TL). For experimental validation, a 50- to $20-{\Omega}$ IT was implemented at a center frequency ($f_0$) of 2.6 GHz for the long-term evolution signal. The measured results were in good agreement with the simulations, showing a return loss higher than 19 dB over a passband bandwidth of 0.63 GHz (2.28-2.91 GHz) and good sharp frequency selectivity characteristic near to the passband. The series coupled TL provides a transmission zero at 5.75 GHz, whereas the shunt coupled TL provides three transmission zeros located at 2 GHz, 3.1 GHz, and 7.14 GHz.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1993년도 하계학술대회 논문집 B
• /
• pp.711-714
• /
• 1993

A predictive current controller for the Battery Energy Stroage System(BESS) based on space vector PWM of transformer coupled inverters is presented. The control method have many advantages such as accurate control, reduced harmonics, good dynamics, improved stability, wide control range, etc,. The simulation results show that the predictive control method with space vector PWM is suitable for the transformer coupled inverters applied to the battery energy storage system.

• ETRI Journal
• /
• 제35권3호
• /
• pp.554-557
• /
• 2013

This letter presents a power amplifier (PA) with an on-chip power detector for 2.4-GHz wireless local area network application. The power detector consists of a clamp circuit, a diode detector, and a coupled line directional coupler. A series inductor for an output matching network in the PA is combined with a through line of the coupler, which reduces the coupling level. Therefore, the coupler employs a metamaterial-based transformer configuration to increase coupling. The amount of coupling is increased by 2.5 dB in the 1:1 symmetric transformer structure and by 4.5 dB from two metamaterial units along the coupled line.

• 반도체디스플레이기술학회지
• /
• 제6권2호
• /
• pp.29-33
• /
• 2007

Low frequency (400 kHz) Ferrite ICP has been proposed for large area processing. Because the coupling coefficient is close to 1, the transformer matching can be adapted to Ferrite ICP. The transformer matching system is simple. In this paper the new matching system by controlling the turns of transformer using relays is proposed for impedance matching. We developed a simple matching system and characterized it when the turns were changed. It was observed that the 2-channel relay is available for transformer matching.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제55권7호
• /
• pp.353-361
• /
• 2006

This paper presents the design scheme of transformer for backlight inverter and discuss the characteristics related to its design, including driving inverter. A few studies have so far been made at design and characteristics analysis of transformer. Therefore, this paper manages the presentation of the advisable design methodology of transformer for backlight inverter supplying CCFL. To verify the proposed method, this paper accomplishes the analysis by FEM coupled with circuit and finally shows that the proposed design method is very useful.

• 전력전자학회논문지
• /
• 제25권1호
• /
• pp.37-43
• /
• 2020

This study proposes a 7kW low-voltage DC-DC converter (LDC) using a coupled inductor (CI) for heavy hydrogen electric transport vehicles. The LDC uses a phase-shift manner for soft switching. SiC-MOSFET is used to reduce the loss of reverse recovery current through the use of a high switching frequency. LDC is require large transformer and inductor because of large output current. The size of transformer and inductor can be reduced by deviding the transformer and inductor into two pieces each. This work presents the experimental results of the proposed circuit.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 C
• /
• pp.1760-1762
• /
• 2002

In this work we develop an equivalent circuit model of TCP(transformer coupled plasma) source and investigate matching characteristic. The developed circuit model includes transmission line, standard-type impedance matching network and displacement current in the plasma source. The impedance of TCP is calculated by previously developed program for various source parameters and dependance of components of matching impedance on the value of source impedance is investigated.