A medium voltage fully controllable solid state switch for Klystrom modulator

The paper will describe the specification, design, production and test of a fully controllable solid state on-off switch in IGCT-technology. (IGCT = Integrated Gate Commutated Thyristor) This type of switches is often used for linear particle beam accelerators and successful in use in several Institutes and National Laboratories to drive long pulse Klystron Modulators. The described solid state switch is rated for 4.4 kVdc, 1850 A peak, 2 ms pulse and 2 Hz repetition rate under normal conditions and can turn-off 3700 A under fault conditions and a max. peak voltage of 9 kV. The IGCT´s used are commercially available devices and have a 91 mm silicon wafer with a monolithic integrated freewheeling diode. To reach a high reliability 3 devices of 4.5 kV blocking voltage are used in series connection which gives the switch one redundant device and a large silicon area to enable a high switch-off current in case of klystron arcing. The rated current of 1850 A is switched continuously at 2 Hz, and therefore air convection cooling can be used. The described switch comes as ready-to-use design including isolated auxiliary power supply, optical triggering and optical feedback.