High Frequency Transformer Winding Power Loss Reduction

当电流流过传统的Transformer绕组时，电流在绕组内不是均匀分布的。在电流具有高集中度的情况下产生高绕组功率损耗，并且在电流具有低集中度的情况下绕组未被充分利用。高电流集中产生高绕组功率损耗，这导致能量转换效率降低和高温。高温降低了Transformer的使用寿命，因此在Transformer设计中必须使用更多的绕组以降低功率损耗。结果，变压器体积大且重，这增加了Transformer的成本，并且不能满足当今对高度紧凑设计的需求。本研究旨在从根本上解决这一问题。研究者初步发现，Transformer绕组中的电流分布总是达到一个最小磁能状态。基于这一发现，一种新的Transformer绕组设计技术正在开发中使用的最小磁能状态和功率损耗的绕组之间的关系。该技术可以使电流比现有技术更均匀地分布在Transformer绕组内。该技术可大大降低Transformer绕组功率损耗，提高Transformer能效，提高Transformer可靠性，降低Transformer成本，提高Transformer功率密度。该技术也可以应用于其他磁性元件。变压器和磁性元件广泛用于许多电子和电气应用领域，例如消费电子产品、工业产品和运输系统。因此，这项技术有望为社会带来重大的科学和经济影响。本研究的目的是发展一种新颖的Transformer绕组设计技术，以最小化Transformer绕组中的功率损耗。 研究人员将研究Transformer绕组中的最小磁能状态，探索最小磁能状态与绕组电流分布之间的关系，并开发一种技术来找到所需的绕组电流或磁动势（MMF）曲线，以最大限度地减少Transformer绕组的功率损耗。 首先研究绕组功率损耗与绕组磁能之间的关系。PI先前已经发现，影响绕组导体内的电流分布和并联绕组导体之间的电流分配的趋肤效应和邻近效应符合最小磁能理论。研究了高频Transformer绕组中最小磁能状态与绕组电流分布或均流的关系。将探索通过最小化绕组之间的磁能来实现最小绕组功率损耗的技术。将开发一种使用最小磁能模型来求解所需的MMF轮廓的方法。一种技术来实现所需的磁动势，无论是串联或并联绕组匝将进行研究。在研究活动中开发的理论和技术可以应用于任何变压器和许多应用中的磁性元件设计。与传统的大规模有限元分析或基于试验的试错法绕组设计方法相比，该研究能够揭示高频变压器绕组电流分布和均流的基本规律。该方法应该能够快速和直接地找到具有最低绕组功率损耗的最佳Transformer绕组设计。该方法对Transformer绕组的设计也有一定的指导意义。该方法不仅可以帮助设计人员了解Transformer绕组内的电流分布和共享，而且还可以使设计人员能够根据所需的电流共享曲线来控制Transformer绕组内的电流。采用该技术可大大降低Transformer绕组中的功率损耗，提高功率密度。初步研究表明，与传统的全交错绕组结构相比，使用有待开发的理论和技术，绕组功率损耗可降低33-41.5%。

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.