Performance Comparison of Nanocrystalline Material with
Ferrite in a 40kW 20kHz Application
Kapila Warnakulasuriya, Carroll & Meynell Transformers Ltd, UK,kapila@carroll-meynell.com
Farhad Nabhani, Teesside University, United Kingdom, F.Nabhani@tees.ac.uk
Vahid Askari, Teesside University, United Kingdom, v.askari@tees.ac.uk
Abstract
In this paper the performance of Nanocrystalline material in comparison with ferrite is evaluated for a high frequency high power transformer core application. The major advantage of Nanocrystalline material over ferrite is its ability to go for higher design flux densities. However, this is limited with increased losses occurring with the increase of operating frequency. The situation is studied for a 40kW, 20 kHz application. Samples of both versions are developed and a performance evaluation is made on the application. Based on the practical outcome a comparison is made in terms of power density per physical parameters such as weight and volume. The cost and manufacturability are also discussed.
1. Introduction
The transformers in electrical systems are responsible approximately to one third of total network losses. These losses are accounted as power quality costs, costs to society and to the environment itself [19]. With the development of power electronics techniques, pulsewidth modulated inverters (PWM) are widely used to control electrical machines, to feed transformers and to interface renewable energy systems. Also in the future DC electric power systems, high power DC –DC converters will play a major role as they will substitute today’s bulky 50/60 Hz transformers [17], [20]. The main purpose of high frequency operation of such power electronics circuits is to reduce the physical size and cost. The implication being that the losses and efficiency become of paramount importance because of the need to remove heat from the small surfaces [16]. High frequency transformers in such a power electronics circuits constitute a major proportion of the weight and losses. Thus, there is a rapid increase in the industry demand for the best optimization of high frequency transformers. The importance of looking into all the options of optimization become further more significant with the increase of amount of power handled. In this paper the design optimization of a 40kW High frequency transformer operating at 20kHz application is discussed. The losses in the core as well as in the windings are analyzed. Theoretical explanations on the principles used in optimizing the core and winding losses are discussed. Attention is given to make a comparison of the performance of nanocrystalline core and ferrite core. The design approach discussed below is used to arrive at optimal designs with each core material.
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