Thermal Design and Optimization of Parasitics for High Power Converters

Abstract

Design of high power converters require deep insight into magnetic, thermal and mechanical parameters of the converter, besides the electrical parameters, for it to function in a desired manner. The high power converters have losses proportional to their power rating; even a highly efficient converter (98%) could have losses as high as >100 kW. It is essential to extract this thermal energy form the system so that the components in the converter do not fail. Extraction of such large quantities of thermal energy is a formidable challenge and has been dealt with in detail in this work. Various options for this process have been discussed. Optimization of the interconnecting bus-bar network in the converter is another important aspect of the design. Minimization of stray inductances and loops lead to lower voltage stresses on the semiconductor devices and proper operation of the converter. Imperfect joints between interconnecting bus-bars form stray resistances which lead to localized heating of the bus-bars. This thermal cycling leads to faulty joints, causing inefficient operation of the converter. To maximize the efficiency of the converter, such interconnection issues have been addressed. Finally, the weight distribution, foot-print and volume of the converter play a key role in its manufacturability and marketability. Special attention has been given to the materials selected in the design process to maximize the life of the converter and ensure correct operation under different ambient temperatures and weather conditions. A well built converter must follow the guidelines laid by the mechanical and thermal aspects of the design process.