• Journal of Power Electronics
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• 제6권3호
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• pp.214-225
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• 2006

The design and performance analysis of a reduced rating autotransformer based thirty-pulse AC-DC converter is carried out for feeding a vector controlled induction motor drive (VCIMD). The configuration of the proposed autotransformer consists of only two single phase transformers, with their windings connected in a T-shape, resulting in simplicity in design, manufacturing and in a reduction in magnetics rating. The design procedure of the autotransformer along with the newly designed interphase transformer is presented. The proposed configuration has flexibility in varying the transformer output voltage ratios as required. The design of the autotransformer can be modified for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The proposed thirty-pulse AC-DC converter is capable of suppressing less than $29^{th}$ harmonics in the supply current. The power factor is also improved to near unity in the wide operating range of the drive. A comparison of different power quality indices at AC mains and DC bus is demonstrated in a conventional 6-pulse AC-DC converter and the proposed AC-DC converter feeding a VCIMD. A laboratory prototype of the proposed autotransformer based 30-pulse AC-DC converter was developed with test results validating the proposed design and system.

• Journal of Power Electronics
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• 제18권6호
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• pp.1920-1929
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• 2018

In order to provide a source for nine phases suitable for 18-pulse ac to dc power, this paper proposes a new structure for a step-up asymmetrical delta-connected transformer for converting three-phase ac power to nine-phase ac power. The design allows for symmetry between the nine output voltages to improve the power quality of the supply current and to minimize the THD. The results show that this new structure proves the equality between the output voltages with $40^{\circ}-{\alpha}$ and $40^{\circ}+{\alpha}$ phase shifting and produces symmetrical output currents. This result in the elimination of harmonics in the network current and provides a simulated THD that is equal to 5.12 %. An experimental prototype of the step-up asymmetrical delta-autotransformer is developed in the laboratory and the obtained results give a network current with a THD that is equal to 5.35%. Furthermore, a finite element analysis with a 3D magnetic field model is made based on the dimensions of the 4kVA, 400 V laboratory prototype three-phase with three-limb delta-autotransformer with a six-stacked-core in each limb. The magnetic distribution flux, field intensity and magnetic energy are carried out under open-circuit operation or load-loss.

• 전력전자학회논문지
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• 제8권6호
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• pp.543-550
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• 2003

본 논문에서는 2대의 다이오드 정류기에 부스트 컨버터를 이용하여 전류의 파형을 능동적으로 만들어 정현파의 입력전류를 얻는 새로운 방식의 고조파 저감방식을 제안한다. 제안한 방식으로 고역률의 전원 품질을 얻을 수 있으며 입력측의 변동에 대한 출력전압의 조정도 가능하다. 또한 저감된 용량을 갖는 3상 오토트랜스포머의 사용으로 기존의 $\Delta$-Y 변압기에 비해 KVA정격이 75% 절감되며 상간변압기도 필요 없다. 본 방식을 소형화와 고품질의 전원이 요구되는 통신용 정류기등에 적용하면 효과적이다. 제안한 방식의 동작원리, 제어 및 설계방법을 기술하고 1.5KW급 시작품으로부터의 실험결과를 제시한다.

• Journal of Electrical Engineering and Technology
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• 제1권3호
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• pp.302-307
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• 2006

The purpose of this paper is to develop an improved three-phase transformer model for ATP and parameter estimation methods that can efficiently utilize the limited available information such as factory test reports. In this paper, improved topologically-correct duality-based models are developed for three-phase autotransformers having shell-form cores. The problem in the implementation of detailed models is the lack of complete and reliable data. Therefore, parameter estimation methods are developed to determine the parameters of a given model in cases where available information is incomplete. The transformer nameplate data is required and relative physical dimensions of the core are estimated. The models include a separate representation of each segment of the core, including hysteresis of the core, ${\lambda}-i$ saturation characteristic and core loss.

• 대한전기학회논문지:전력기술부문A
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• 제52권9호
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• pp.493-499
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• 2003

This paper presents exact Autotransformers(ATs)-fed AC electric Railroad system modeling using constant current mode for locomotives. An AC electric railroad system is rapidly changing single-phase load, and at a feeding substation, 3-phase electric power is transferred to paired directional single-phase electric power. As the train moves along a section of line between two adjacent ATs. The proposed AC electric railroad system modeling method considers the line self-impedances and mutual-impedances. The constant current mode model objectives are to calculate the catenary and rail voltages with the loop equation. When there are more than one train in the AC electric railroad system, the principle of superposition applies and the only difference between the system analyses for one train. Filially, this paper shows the general equation of an AC electric railroad system, and that equation has no relation with trains number, trains position, and feeding distance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.853-855
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• 1993

In this paper, a further improved system obtaining very low distorted waveforms of input ac currents of three phase rectifier circuit is proposed. The proposed system consists of an uncomplicated 24 pulse diode bridge rectifier that is transformerless, by adding only switching circuit which consists of two switchs to conventional system. Also to optimum the effectiveness or the harmonic reduction, the optimum turn ratio of an autotransformer and the optimum switching control angle are decided by computer simulation. And then, the voltage waveform obtained has a total harmonic distortion of 8.1%, and the predominant harmonics 23th and 25th. This paper describes operation principle, analysis of the waveforms of input voltage and current. The theoretial results are verified through simulation.