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Isolation transformer

About: Isolation transformer is a research topic. Over the lifetime, 8145 publications have been published within this topic receiving 72396 citations.


Papers
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Proceedings ArticleDOI
20 Jun 2004
TL;DR: In this article, an isolated bidirectional DC/DC Cuk converter with high power density, zero input/output current ripples, and symmetrical design is presented, where the magnetic components of the converter, which include the input inductor, the output inductor and the isolation transformer, are assembled together in one magnetic structure.
Abstract: In this paper, an isolated bidirectional DC/DC Cuk converter featuring high power density, zero input/output current ripples, and symmetrical design is presented. The magnetic components of the converter, which include the input inductor, the output inductor, and the isolation transformer, are assembled together in one magnetic structure. The magnetic assembly is modeled and designed using the gyrator-capacitor (G-C) approach. Simulation and experimental results are presented to verify the converter performance in both forward and backward modes of operation. The effect of the switching frequency on the percentage current ripples is discussed.

19 citations

Patent
17 Apr 1998
TL;DR: In this article, a ground fault detection circuit was proposed to detect ground fault currents in the transformer secondary and deliver a ground-fault detection signal to the primary circuit via an optical isolation barrier.
Abstract: A transformer control circuit (10) which includes a ground fault detection circuit (52) that detects ground fault currents in the transformer secondary (42, 44) and delivers a ground fault detection signal to the primary circuit. This circuit derives power from the secondary winding (42, 44) and transmits the ground fault detection signal through an optical isolation barrier (54), thus avoiding the use of an auxiliary transformer. The ground fault detection circuit further includes safety features for detecting whether AC power is being supplied without earth ground being connected, and/or whether there is an undesired electrical connection between a transformer output connection and earth ground, which would defeat the ground fault detection circuit.

19 citations

Proceedings ArticleDOI
15 Oct 2007
TL;DR: This paper deals with a middle frequency resistance spot welding system that consists of a semiconductor input converter, a single phase welding transformer with one primary coil and two secondary coils, and a full-wave output rectifier connected to the transformer's secondary coils.
Abstract: This paper deals with a middle frequency resistance spot welding system. It consists of a semiconductor input converter, a single phase welding transformer with one primary coil and two secondary coils, and a full-wave output rectifier connected to the transformer's secondary coils. The unwanted current spikes often appear in the transformer's primary coil current during steady state operation, which was proven by measurements. The numerical analysis, based on a nonlinear model of the discussed system, has shown that these current spikes are caused by the interaction among asymmetrical design of the transformer, its magnetically nonlinear behavior, and unequal characteristics of the diodes in the output rectifier. This undesirable phenomenon can be efficiently avoided by the passive or active approach proposed in this work. The passive approach is based on the correct positioning of carefully chosen diodes in the output rectifier, while the active one includes the closed loop welding current control and the closed loop control of flux density in the transformer's iron core. The consequent employment of the active approach makes possible reduction of the transformer's iron core size at the same power of the spot welding system.

19 citations

Journal ArticleDOI
Piotr Czyz1, Thomas Guillod1, Florian Krismer1, Jonas E. Huber1, Johann W. Kolar1 
TL;DR: In this paper, the authors investigated the achievable efficiency of an optimized 166kW / 7 kV air-core transformer (ACT), which is a core part of a DC Transformer (DCX), i.e., an unregulated DC-DC SST with a voltage scaling defined by the transformer turns ratio.
Abstract: The galvanic isolation of solid-state transformers (SSTs) is typically realized with a medium-frequency (MF) magnetic-core transformer (MCT). Previous demonstrations indicate that achieving highly power dense and lightweight MCTs imposes several challenges on the design because of stringent requirements related to insulation and cooling. This work investigates the achievable efficiency of an optimized 166kW / 7 kV air-core transformer (ACT), which is a core part of a DC Transformer (DCX), i.e., an unregulated DC-DC SST with a voltage scaling defined by the transformer turns ratio. The ACT features relatively low complexity of the construction, comparably high coupling values, and high efficiency. Modeling, optimization, and construction of the realized ACT are explained and guidelines regarding insulation, cooling, and shielding of the magnetic stray flux are discussed in detail. Furthermore, the prototype is experimentally validated to demonstrate its full functionality. In the investigated DCX, which is based on a series resonant converter (SRC) topology, the realized ACT is found to achieve a full-load efficiency of 99.5% and an unprecedented gravimetric power density of 16.5 kW/kg. With the use of 10 kV SiC MOSFETs, the complete DCX is estimated to reach an efficiency of 99% at 166kW output power.

19 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the differences in dielectric design and insulation coordination required for a transformer and their effect on the operation of large power transformers, and discuss the impact of these differences on the performance of large transformers.
Abstract: The dielectric design and insulation coordination required for a transformer are predominantly a function of the requirements of the user. Applicable standards provide both a methodology and criteria through which the industry can then construct and proof test a unit. This permits the user to coordinate the insulation of the transformer with its application in a power system. However, the transformer is then subjected to the actual conditions and operating practices at its installed location. These conditions, and the passage of time, present challenges to the dielectric design different from those of the factory. This paper discusses those differences, and their effect on the operation of large power transformers.

19 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202313
202251
202144
2020151
2019211
2018266