Press-pack IGBTs for HVDC and FACTs

Abstract

The popularity of insulated gate bipolar transistors (IGBTs) for use in high-voltage direct current (HVDC) transmission and flexible AC transmission systems (FACTS) is increasing. Unfortunately, for these applications wire-bond IGBT technology has a number of shortcomings, such as insufficient current ratings for the most powerful schemes, and inability to fail to short-circuit. Press-pack IGBT technology, conversely, offers increased current ratings, and an inherent short-circuit failure mode, making it a more attractive choice for HVDC and FACTS. However, the design and manufacture of these devices requires a comprehensive understanding of the unique technical challenges, which differ markedly from those for wirebond modules or traditional pressure contact devices. Specific challenges include providing a high degree of mechanical protection for the IGBT chip against normal operating stresses. Furthermore, it is essential to achieve uniform contact pressure across each chip surface to ensure optimum performance. To achieve this, manufacturers have designed products that use rigid copper electrodes manufactured to tighter tolerances than for other pressure contact devices, such as thyristors, and products that use compliant electrodes, incorporating spring assemblies. Dynex is in the advanced stages of development of press-pack IGBT technology with demonstrated robust solutions for the technical challenges outlined in this paper. Design success has been achieved through the use of state-of-the-art simulations in conjunction with a long history of manufacturing expertise for bipolar and IGBT products. Finally, multiple press-pack IGBT variants are currently undergoing evaluation tests prior to product release.