Isolation transformer

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

Self-Oscillating Resonant Converter With Contactless Power Transfer and Integrated Current Sensing Transformer

Abstract: In this paper, an integrated transformer is proposed to provide current sensing in the primary side and passive current phase detection for a self-oscillating contactless resonant converter (SOCRC). The proposed transformer integrates power transfer and current sensing. By using the secondary current phase of a series/series-compensated resonant converter in the control of the inverter, better output controllability, dynamic response, and self-adaptability can be achieved simultaneously. The integrated current sensing winding, being a crucial part of SOCRC, is analyzed in detail. In order to make the output voltage insensitive to the clearance and misalignment conditions, the requirement of the new integrated transformer is given. Experimental results of an 80-W SOCRC prototype verify the analytical results.

Flux‐based turn‐to‐turn fault protection for power transformers

Abstract: Since the internal turn-to-turn faults (TTFs), as a common cause of the transformer failures, result in minor changes on terminal currents/voltages, they maybe undetected by the conventional protective relays. In this study, a simple, sensitive and robust linkage flux-based technique is proposed to protect the power transformers against TTFs. In this approach, some separated multi-turn windings as search coils (SCs) have to be wrapped around the transformer core legs to sense the related passing flux. Since passing equal flux through a transformer core leg in normal condition induces equal voltages in the related SCs, variation of the induced voltages indicates the fault occurrence in that phase. Against the traditional differential protection schemes, current transformer error and saturation, tap changer operation, energising inrush current, over-fluxing etc. cannot impact the proposed technique performance. Therefore, it can be introduced as a comprehensive protection technique for power transformers.To confirm the proposed technique performance, it is tested on a real 50 kVA, 20 kV/400 V three-phase distribution transformer, in various conditions, too.

A new method for purposes of failure diagnostics and FRA interpretation applicable to power transformers

Abstract: To diagnose electrical and mechanical failures on the active part of power transformers efficiently, different state-of-the-art testing methods are recommended to be performed since transformers are complex devices Measurement results can be equivalent electrical parameters relating to the windings (resistances, leakage/zero-sequence inductances and capacitances), core magnetic property (via induced voltages and exciting currents) or terminal frequency responses (standard FRA tests) Consequently, it is not easy for normal users to implement all necessary measurements, which require much time and training skills due to use of different specialized testing devices To help users for fast and efficient diagnostics, the paper presents a new method in determining most electrical parameters of the transformer active part based on only the driving-point impedance tests performed by means of a vector-network analyzer More importantly, the method can be applied to give a FRA interpretation based on physical electrical parameters, which is currently requested from relevant standards The physical FRA interpretation is found to be useful in calculating immeasurable series capacitances of windings in transformer bulk, which is still problematic until now Investigation on a large distribution transformer shows that the new method is simple, less time consuming but efficient

Design of an electronic power transformer

Abstract: For the distribution of electrical energy in Germany, application-specific transformers with ratings of 110/20 kV, 110/10kV, 40 MVA, 50 Hz are typically in operation. Due to their weight, these transformers can only be transported with great expense (usually by rail). Therefore a considerable number of reserve transformers has to be held in stock in each distribution area, to guarantee power reliability to utility customers by quick replacement. To reduce assets, a universal, mobile and flexible (adjustable to different medium-voltage levels and truck movable) transformer reserve unit is desired by utility companies. The modular design of an electronic power transformer for this purpose is given in this paper. Based on power electronics, additional features like fast voltage regulation, reactive power compensation, ride-through capability etc. are described.

Modeling, simulation, and experimental verification of soft-switched bi-directional DC-DC converters

Abstract: In this paper, an extended averaged model is developed for a soft-switched bi-directional DC-DC converter for high-power applications. The proposed technique can be applied to other bi-directional DC-DC power converters with a high-frequency isolation transformer. Simulation results of Matlab/Simulink using the proposed average model are compared to those of detailed circuit simulation and experimental results to confirm the validity of this technique.