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The presentation will give an overview of the design, construction, test and reliability of a solid state switch assembly used for magnetic forming applications. In 2005 a prototype of a reverse conducting semiconductor switch for 210 kA at 100 µs damped sine wave discharge and 21 kV dc was designed to be used in an experimental system at the Fraunhofer Institute at Chemnitz (Germany). The aim was to show the industry that semiconductors can be used for this type of applications. Precautions in the design stage have to be taken to reach high operational lifetime. The presented prototype switch was designed for an expected lifetime of 20 000 shots under nominal and 1 000 shots under short circuit conditions of 420 kA. After successful commissioning, further tests were done on separate semiconductor devices to verify under which conditions the lifetime could be increased to several million shots for the given application. For this verification, ABB has done extended device tests over more than one million shots and the wafers were analysed. The results of the reliability test are part of this presentation. It will be concluded that proper designed solid state switches are economically feasible, free from maintenance and despite higher initial cost are more reliable and superior to any other technology existing today.PACS numbers: 84.30.Jc, 84.32.Dd Device technologyThe semiconductor devices selected for this application are based on silicon wafers of the integrated gate commutated thyristor (IGCT) or gate turn-off (GTO) technology and optimized as capacitor discharge devices. As there is no turn-off requirement, the devices are fully optimized for fast switch-on with high di/dt capability of up to 25 kA/µs. Because some applications have a damped sine wave it is possible to integrate a diode monolithic on the same silicon wafer. In Fig. 1 the low inductive housing of the semiconductor device is shown. Figure 2 shows the 91 mm silicon wafer, Fig. 3 the complete semiconductor device and Fig. 4 the complete switching device including integrated driver unit. The switching capability of the asymmetric blocking (V drm = 4500 V, V rrm = 17 V) device is up to 150 kA at 100 µs and for the reverse conducting version with integrated diode (V drm = 4500 V/V rrm = 0 V) up to 100 kA at 100 µs. Triggering is done by a very strong gate-pulse in the range of approximately. 600 A and di/dt of 1 kA/µs. The driver units are designed (986)

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