Compact 12.5 MW, 55 kV solid state modulator

Summary form only given, as follows. The paper will describe a modulator system developed by the Marconi Applied Technologies High Voltage Engineering Group for driving high peak power magnetrons and klystrons. The modulator unit is a compact (0.1 M3 and 91 Kgs), fully integrated system, with an output capability of 55 kV at 250 A. Pulse widths in the range 0.5 uS to 6 uS at duties of up to 0.1%. The modulator switch is of the direct or active switched type, using a series/parallel bank of Mosfets, arranged into 75 modules, to partially discharge an integral capacitor bank into the load. The duty cycle at the output is an amplified representation of the low level drive waveform applied to the trigger input and is not limited to a regular pulse train. The modulator system includes a microprocessor based control system, incorporating all support LT and heater supplies, a specially developed capacitor charge power supply incorporating a close loop control system regulating on peak current and the high voltage switch unit. Thus providing an end user philosophy of "Three-phase mains power & trigger input for a microwave tube drive output". The modulator is cooled by, simple forced oil system with an integral oil/water heat exchanger. The paper will discuss the overall design philosophy, the methods of realizing key components, such as trigger generation/steering and the floating drives to modules. Fault detection and monitoring will be discussed for fault working during load arc/load short circuit conditions. CAD and FE tools used during the development and some of the results from system/life test programs will be discussed. Future expansion plans and adaptation of the system will be outlined, including the use of alternative switch devices (such as IGBT\´s) and operation with none uniform high duty cycle burst waveforms.