Reliability of Solid State Switches Used in High Current Discharge Applications

Abstract

The presentation will give information about the long term reliability of semiconductor components which are used in high current, high di/dt discharge switches as they are used in systems for electro-magnetic forming. Prototype equipment for laboratory use has shown the capability of the switches and equipment to fulfil the requirements requested by the end-users. This however is not enough to be used in the industrial production lines under continuous and repetitive heavy load conditions. Because of the relative high lifetime expectations of the durable equipment used for magnetic forming in the automotive industry the life-time of the semiconductor switches, the inductive loads and the capacitor banks are becoming an issue. The presentation will only describe the semiconductor reliability. A prototype system for 21 kVdc and pulse current of 210 kA was designed and built in the year 2005 by Siemens for the Fraunhofer Institute in Chemnitz, Germany. The semiconductor switch was supplied by ABB Switzerland Ltd. For this experimental machine only low repetition rates of one shot per several minutes and a limited expected life-time of approx. 15.000 20.000 shots was acceptable for the experimental work. The requirement from the automotive industry however is at least one shot per 15 seconds and an operational life-time of >= 2 Mio shot at the mentioned power level. During the last year ABB has done extensive tests to evaluate the behaviour of the semiconductor components used in high current solid state switches under the specific application conditions for production processes. In the presentation the test results of high current semiconductor devices are described for 250.000 shots and 1 Mio shots, and recommendations for reliable solid state switch designs are given. Keywords Semiconductor