A Pulsed High-Voltage Modulator with Partial Discharge of the Storage Capacitor

Abstract

For stationary high-voltage pulsed devices, which do not necessarily have to comply with stringent requirements for their weight and dimensions, a modulator with partial discharge of the capacitive storage can be competitive to a modulator with complete discharge of the capacitor. The switch shall be rigidly controlled and have a low forward voltage drop on the open device; the thermionic cathode operating in the space charge mode shall ensure the specified pulse duration and repetition rate. With the new high-voltage modulator tubes, electron-beam valves featuring small power losses at the anode, and high-perveance electro-optical systems, for example, an EBV 50/100 system, used as a “rigid” switch, it becomes possible to design series or parallel modulator circuits with a capacity of more than 1 MW, which are quite competitive to the schemes synthesized based on a large number of series-connected relatively low-voltage semiconductor switches. If properly calculated using well-known techniques, such a modulator can generate pulses the parameters of which are almost independent on the load resistance varying in a wide range, and the power circuit themselves are insensitive to the effect of any external electromagnetic or X-ray radiation. Two basic modulator circuit arrangements are considered: a parallel one, which generates a negative polarity pulse, and a series one, generating pulses of both positive and negative polarity. The modulator’s load resistance shall be no less than 10 times the anode-cathode resistance of the open switch. For the possibility of determining, in a prompt and vivid manner, the limit values of the switch operating mode and the load resistance, and for optimizing the modulator’s nominal electrical parameters, the electric circuit is simulated on a computer using the EWB program.