• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.10
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• pp.1344-1352
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• 2018

In this paper, we propose a two-port S-parameter data to diagnose the fault conditions of a single-phase transformer. Using the S-parameters we can measure the reflection and transmission characteristics of signal power at the port of a transformer, which can also be converted into ABCD parameters and Z parameters through a well-known conversion formulas. Transformer fault diagnoses can be performed based on the intuitive and qualitative/quantitative characteristics of the these parameters. In addition, we can obtain wide frequency characteristics at the primary and secondary sides of the transformer, which can be used to get time domain responses using the inverse Fourier transformation with some specific input waveform. In order to verify the effectiveness of the proposed method, the fault conditions were analyzed in simulation and experiment for 3 kVA single phase transformer with 15: 5 turns ratio, and the validity of the proposed method was verified.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.31 no.3
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• pp.117-124
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• 2008

Ultra-high voltage transformer industry has characteristic of small quantity batch production system by other order processing unlike general mass production systems. In this industry, observance of time deadline is very important in market competitive power security and company continued existence. The transformer winding is a process that rolls a coil is coated with an electric insulation material in order to generate the required voltage using the voltage fluctuation. The winding process is very important production process in the extra-high voltage transformer manufacturing industry because winding process is core process that occupy weight about half of whole process and is process that decide current ratio of transformer. This paper proposes a statistical calculation and control method of planned leadtime on the basis of real data and informations for the A company in transformer winding process. Moreover, we develop unit process scheduling system.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.101-105
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• 2018

Shortage of electric power occurs frequently along with increased electric power demand. ESS is a precaution to solve this issue. Household ESS has a capacity of approximately 3 kW/7 kWh. Household ESS batteries are typically designed with nominal voltages between 40 and 50 V. To connect household ESS with a 220 V AC system, low battery voltages in power conditioning system (PCS) should be boosted. To boost low battery voltage and match it with AC grid voltage, the use of a transformer for a commercial frequency can be considered. To attenuate switching harmonics of the household single-phase ESS-PCS, LC filter can be installed in two positions: on the primary side or on the secondary side of a transformer. A method has been used generally in single-phase inverters for the ESS-PCS. In another method, however, the output efficiency of the ESS-PCS may be decreased. Parasitic components of the transformer can affect voltage losses, when the square wave with the switching frequency in the ESS-PCS is passed through the transformer windings. In this work, the characteristics of the transformer according to the position of an LC filter are investigated for household single-phase ESS-PCS.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.11
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• pp.948-952
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• 2007

In this study, a low temperature sintering multilayer piezoelectric transformer for a DC-DC converter was manufactured using $(Pb,Ca,Sr,)(Ti,Mn,Sb)O_3$ ceramics. Its electrical properties were investigated according to the variation in frequency and load resistance. The voltage step-up ratio of the multilayer piezoelectric transformer showed a maximum value at a resonant frequency of input part and increased with an increase of load resistance. The efficiency of the multilayer piezoelectric transformer showed the highest value at a load resistance of 17 $\Omega$. The output power was increased with increasing input voltage. Temperature increase of the multilayer piezoelectric transformer was increased with the increase of output power. At the load resistance of 17 $\Omega$, the multilayer piezoelectric transformer showed the temperature rises of about $20^{\circ}C$ at the output power of 18 W, and stable driving characteristics.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.5
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• pp.193-200
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• 2004

In this study, we propose a small high voltage power supply, which uses a half-bridge ZCS resonant and Cockroft-Walton circuit as its ESP (Electrostatic Precipitator). This power supply transfers energy from the ZCS resonant inverter to the step-up transformer. The transformer secondary is then applied to the Cockroft-Walton circuit for generating high voltage as a discharging source of electrodes. It is highly efficient because its amount of switching losses are reduced by virtue of the current resonant half-bridge inverter, and also due to the small size, low parasitic capacitance in the transformer stage owing to the low number of winding turns of the step up transformer secondary combined with the Cockroft-Walton circuit. Using this power supply, experiments have been carried out as a function of the switching frequency and duty ratio in order to investigate the smoke removal characteristics. From these results, the best operational condition is obtained at the switching frequency of 9 kHz and the duty ratio of 50% in this ESP.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1984-1986
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• 2000

In pulsed-power techniques. Marx generator is generally used for the high-power device. but this generator has insulation and spatial problems. So we will suggest a pulse transformer that has a small size to generate the high voltage pulse instead of Marx generator. In this paper, Pulse duration is 4 [${\mu}s$] and the ratio of input and output voltage is 40[kV]/200[kV](step-up ratio=5). The output voltage and the process of pulse compression for pulse circuit are simulated by EMTP (Electro-Magnetic Transient Program). The secondary voltage of pulse transformer is about 200[kV] and pulse width is 4[t/s]. When the secondary winding of the pulse transformer is saturated. the pulse width is 1.25[${\mu}s$]. We selected dummy load 50[$\Omega$] for impedance matching. The pulse voltage of dummy load is 100[kV] and pulse width is 500[ns].

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.220-226
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• 2000

The piezoelectric material for piezoelectric transformer needs the high electromechanical coupling factor( $k_{p}$) the piezoelectric constant( $d_{33}$) and the mechanical quality factor( $Q_{m}$)in order to obtain high voltage step-up ratio and low temperature rising. In this study the piezoelectric transformers were fabricated using Pb［$Zr_{0.45}$/ $Ti_{0}$48//L $u_{0.02}$(M $n_{1}$3//S $b_{2}$3/)$_{0.05}$］ $O_3$(PMS-PZT) and Pb［Z $r_{0.25}$/ $Ti_{0.375}$(M $g_{1}$3//N $b_{2}$3/)$_{0.375}$］ $O_3$+0.5wt%Mn $O_2$(PMN-PZT) ceramics. The piezoelectric properties of PMS-PZT and PMN-PZT were measured. The voltage set-up ratios of the piezoelectric transformers using PMS-PZT and PMN-PZT were the value of 15, 20 respectively under 100$_{KΩ}$ in Rosen type transformer.r.ormer.r.r.r.r.r.r.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.847-851
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• 2000

In this study, contour-vibration-mode Pb($Ni_{1/2}$,$W_{1/2}$)$O_3$-Pb(Zr,Ti)$O_3$ piezoelectric transformers for driving a 28W(T5) fluorescent lamp were fabricated to the modified filter structure with ring and dot electrodes which has been developed for application in 455kHz AM radios. The piezoelectric transformers were fabricated to the size of $31.5$\times$31.5$\times$2.5$mm^3$ with the variations of ring/dot electrode area ratio. Driving of piezoelectric transformer was carried out with input region for the ring electrode and output region for the dot electrode. The electrical properties and characteristic temperature rises caused by the vibration were measured at various load resistances. A 28 W fluorescent lamp, T5, was successfully driven by the fabricated transformer. The transformer with ring/dot electrode area ratio of 1.83 exhibited the best properties in terms of output power, efficiency and characteristic temperature rise, 30.95 W, 97.57% and8.3$^{\circ}C$ respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.595-600
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• 2023

In this paper, a modified equations of the T-equivalent circuit of the transmission line with the arbitrary electrical length is suggested. The suggested equations can be calculated without limitation of the equal branch-line. So, a modified T-equivalent circuit can be made with the arbitrary position of the open-stub. Also, the modified T-equivalent circuit can be applied in the arbitrary electrical length and impedance of the transmission line. For example, the λ/4 impedance transformer is converted with 4 divided T-equivalent circuit. The converted λ/4 impedance transformer has the size reduction ratio of 39.4%.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.43-50
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• 2003

This presents a fault detecting method for a power transformer based upon a neural network. To maintain a normal relay operating conditions, external winding faults of a power transformer and magnetic inrush have been tested under consideration of the EMTP/ATP software and internal faults of power transformer have been tested by the EMTP/BCTRAN software. The neural network has been evaluated by the proposed fault. Input variables of the neural network for the proposed model can be obtained from fundamental currents, restraining and operating currents. This algorithm uses back-propagation and the ratio of a restraining current and an operating current as relay input parameters. The ratio may enhance the fault detection since the restraining currents increase rapidly at external faults. The proposed detecting method has been applied to the practical relay systems for transformer protection. As a result, the proposed detecting method based on the neural network has been shown to have better characteristics.