High Frequency Transformer Winding Power Loss Reduction

University Of Florida, Gainesville FL

Investigators

Abstract

When electrical current flows through conventional transformer windings, the current is not evenly distributed within the windings. High winding power losses are generated where the current has high concentration and the winding is not fully utilized where the current has low concentration. High current concentration generates high winding power loss which leads to reduced energy conversion efficiency and high temperature. High temperature reduces transformer lifetime, so more windings must be used in transformer design to reduce power loss. As a result, transformers are bulky and heavy which increases transformer cost and cannot meet today's demand for highly compact designs. This research pursues a fundamental solution to this problem. It has been preliminarily discovered by the investigator that the current distribution within transformer windings always reaches a minimum magnetic energy state. Based on this discovery, a novel transformer winding design technique is being developed using the relationship between the minimum magnetic energy state and power loss in the windings. The technique can make current much more evenly distributed within transformer windings than is possible with existing techniques. The technique can greatly reduce transformer winding power loss, improve transformer energy efficiency, improve transformer reliability, reduce transformer cost and improve transformer power density. The technique can also be applied to other magnetic components. Transformers and magnetic components are widely used in many electronics and electrical application areas such as consumer electronics, industry products and transportation systems. Thus this technique is expected to bring significant scientific and economic impacts to society. The education plan educates electrical engineering students and promotes diversity. The goal of this research is to develop a novel transformer winding design technique to minimize power loss in transformer windings. The researchers will investigate the minimum magnetic energy state in transformer windings, explore the relationship between the minimum magnetic energy state and winding current distribution and develop a technique to find desired winding current or magnetomotive force (MMF) profiles to minimize transformer winding power loss. The relationship between the winding power loss and magnetic energy windings will be first investigated. The PI has previously found that skin and proximity effects which influence the current distribution within winding conductors and the current sharing among parallel winding conductors comply with the minimum magnetic energy theory. The relationship between the minimum magnetic energy state and the winding current distribution or sharing in high frequency transformer windings will be investigated. A technique to achieve the minimum winding power loss by minimizing the magnetic energy among windings will be explored. A method to solve for the desired MMF profile using the minimum magnetic energy model will be developed. A technique to implement the desired MMF to either series or parallel winding turns will be studied. The theory and techniques to be developed in the research activity can be applied to any transformers and to magnetic component design in many applications. Compared with conventional extensive finite element analysis (FEA) or experiment-based trial-and-error winding design methods, the research can reveal the fundamentals of the winding current distribution and sharing in high frequency transformers. The method should be capable of quickly and directly find the best transformer winding design with the lowest winding power loss. The method should also provide useful guidance in transformer winding design. The methodology will not only help designers understand the current distribution and sharing within transformer windings but also give designers capability to steer the currents within transformer windings based on the desired current sharing profiles. With this technique, the transformer's power losses in windings can be greatly reduced and its power density can be greatly improved. Preliminary research shows that compared with conventional fully interleaved winding structure, 33-41.5% winding power loss reduction should be achievable using the theory and techniques to be developed.