High-voltage Transformer Design Research Articles

Lightweight High-Voltage Power Converters for Electroaerodynamic Propulsion

Recent studies in electroaerodynamic (EAD) propulsion have stimulated the need for lightweight power converters providing outputs at tens of kilovolts and hundreds of watts <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> – <xref ref-type="bibr" rid="ref3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> <xref ref-type="bibr" rid="ref4" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[4]</xref> . This article demonstrates a design of a lightweight high-voltage converter operating from a 160–225 V dc input and providing dc output of up to 565 W at 40 kV. It operates at around 500 kHz and achieves a specific power of 1.15 kW <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot {\text{kg}}^{-1}$</tex-math></inline-formula> . High-voltage converters generally comprise an inverter, a step-up transformer, and a rectifier, with the large needed voltage gain distributed among these stages. Several means of realizing these stages are compared in terms of weight. The weight of the converter is minimized by properly selecting and optimizing the design and the voltage gain of each stage within the constraints of device limitations and losses. A prototype circuit is developed based on this approach and used to drive an EAD propulsion system for an unmanned aerial vehicle. Moreover, this article also presents approaches to further improve the specific power of such converters, including better diode utilization and more flexible high-voltage transformer design. In addition to addressing the needs for EAD, this research can potentially benefit the development of lightweight high-voltage converters in many other applications, where weight and size are important.

High Voltage Transformer design based on Flyback Switching Power Supply

The single source generator could change the frequency and duty cycle of the pulse to control the voltage of output in flyback switching power supply. A variety of methods and calculations could be used to design high voltage transformer, such as AP method that will be used in this transformer, kg method and KRP method. In this paper, the process of how to select the magnetic core and the other parameters of the transformer will be discussed step by step. At first, the voltage of output will be over two thousand and five hundred voltage. The single source generator changing the frequency and duty cycle, the voltage of output will stay stability on five hundred voltage. The seize of the transformer is smaller than that has been used, so it will be beneficial for the circuit integrated.

Efficiency Optimization by Considering the High-Voltage Flyback Transformer Parasitics Using an Automatic Winding Layout Technique

This paper presents an efficiency optimization approach for a high-voltage bidirectional flyback dc-dc converter. The main goal is to optimize the converter for driving a capacitive actuator, which must be charged and discharged from 0 V to 2.5 kV dc and vice versa, supplied from a 24 V dc supply. The energy efficiency is optimized using a proposed new automatic winding layout (AWL) technique and a comprehensive loss model. The AWL technique generates a large number of transformer winding layouts. The transformer parasitics, such as dc resistance, leakage inductance, and self-capacitance are calculated for each winding layout. An optimization technique is formulated to minimize the sum of energy losses during charge and discharge operations. The efficiency and energy loss distribution results from the optimization routine provide a deep insight into the high-voltage transformer design and its impact on the total converter efficiency. The proposed efficiency optimization approach is experimentally verified on a 25 W (average charging power) with a 100 W (peak power) flyback dc-dc prototype.

트랜스포머의 자가공진 특성을 이용한 고전압 트랜스포머 설계

In this paper, self-resonant characteristics of transformers were analyzed in accordance with changes of characteristics regarding to the stray capacitance, the volume of winding and the winding ratio were organized by formulas. Generally, the stray capacitance is considered as an unnecessary factor in processing transformers design as well as one of the inherent characteristics. In particular, these characteristics can be appeared clearly in the high frequency driving and Electrical resonance occurs in transformer, according to coupling with a magnetic factor at a particular frequency. In the case of high-voltage output applications, such as medical equipments, It is required to output high-voltage gain. Therefor, If Self-Resonant Characteristic is applied to High-Voltage transformer design, Not only the transformer and circuit but also related the system size can be reduced. So we propose it as one of additional high voltage transformer design methods.

Transfer of transient surge voltage through XLPE cable winding transformer (Dryformer) circuits

Experiment and simulation results of conventional transformer design have shown that there are considerable differences in the characteristics of the surge voltages that are important in deciding the transferred voltages, depending on whether it is from primary to secondary or vice versa. Dryformer is a new technological advance of dry power transformer, which is constructed from XLPE insulated high voltage cables as its winding, and is designed to provide a direct link between ultimate customers and transmission systems in one step transformation [Leijon M, Andersson T. High and dry—dryformer, an innovative high-voltage transformer design that, eliminates the need for oil, promises a host of performance and environmental benefits. IEE Rev 2000:9–14. [1]; Leijon M, Dahlgren M, Walfridsson L, Ming L, Jaksts A. A recent development in the electrical insulation systems of generators and transformers. IEEE Electr Insulat Mag 2001;17(3):10–15. [2]]. It is important therefore to have a better understanding of Dryformer behaviour in regard to transient surge voltage transfer between its circuits. This paper presents the application of a high frequency model for the study of transient surge voltage transfer between the Dryformer circuits due to surges having various steepness, amplitude and duration characteristics, which are expected in practise. The model is based on the creation of an RLCG network that gives the same admittance function as that obtained experimentally at the transformer terminals [Manyahi MJ, Leijon M, Thottappillil R. Transient response of transformer with XLPE insulation cable winding design (Dryformer). ELSEVIER Electr Power Energy Syst 2005;27(1):69–80.]. The validity of the formulated model has been verified by comparing the model predictions with experimentally obtained voltage transfer function. The model is successfully applied in estimating the threat levels posed to Dryformer winding and customer connected equipment due to transient overvoltages.

Transient response of transformer with XLPE insulation cable winding design

Significant advances in XLPE insulation cables that have higher electric field strength withstand capability have made it possible to apply these high voltage (HV) cables as windings in generators and transformers. Therefore, the recent advent of HV generator (Powerformer) that can be connected directly to the power transmission line has motivated the design of HV transformer (Dryformer) that performs one step transformation from transmission to distribution voltage levels. Since the dryformer will be connected directly to transmission lines, they will be subjected to transients resulting from direct and indirect lightning strikes as well as fast switching surges from Gas insulated circuit breakers. This paper presents the results of experimental studies on the cable winding power transformer (Dryformer) to study its response to various transients. Experimental investigations have been carried to obtain the transformer model parameters based on terminal measurement of admittance functions using Network Analyser, and hence for comparing the model predictions with experimentally obtained responses. The model has been successfully used in estimating the dryformer transient responses at its terminals due to surge application of various front times and peak amplitudes that are representative of lightning and switching caused transients. Experiment and simulation results show that there are considerable differences in the transient response characteristics of dryformer windings as compared to that of transformers with traditional winding design. These differences on transient responses are discussed in perspective of their basic difference in winding design features.

High and dry

In this paper the authors describe Dryformer, an innovative high-voltage transformer design that, by eliminating the need for oil, promises a host of performance and environmental benefits.