GB1038409A - Voltage breakdown arc detection system for waveguides - Google Patents

Abstract

1,038,409. Transistor switching circuits; protecting valve circuits. RAYTHEON CO. Jan. 16, 1964 [Feb. 7, 1963], No. 2032/64. Headings H3T and H3W. [Also in Division H2] Arcing in a waveguide 20 is detected by determining the difference between the magnitudes of the micro-wave energy on each side of the arc. In Fig. 1 couplers 21, 29 are connected to the output port 17 of a high power amplifier 16, e.g. a klystron or magnetron, and to the load end of the waveguide 20, the couplers housing microwave detectors, e.g. rectifiers, 25, 30 providing respectively negative and positive output signals. These signals are applied to a resistance network such that when the signals are unbalanced due to an arc, a negative voltage signal is applied to the grid 47 of the first section of a double triode 45 biasing that section towards cut-off. The resulting positive voltage appearing at the junction of resistors 53, 54 turns on a thyratron 71 to produce a positive output signal across a resistor 94. Should, however, the detector 25 fail, a positive voltage signal is applied to the grid 47 causing the first section to conduct more heavily so that the other section of the double triode conducts less, resulting in the turning on of a thyratron 80 to produce the output signal across resistor 94. In either case, the output signal turns on a controlled rectifier 90 to provide a negative pulse to the gate and anode circuits of a controlled rectifier 120. The rectifier 120 is turned off, so that the voltage drop across a resistor 124 disappears and a ferrite switch 14, maintained in the " on " condition by this voltage drop, is placed in the "off" condition to cut-off the supply of energy to the amplifier and waveguide. The rectifier 90 remains turned on for a short period until charged capacitors 108, 110 have discharged. The rectifier 90 then turns off and a transistor 101 becomes conducting to recharge these capacitors. The rectifier 120 then turns on, after a cpacitor 115 has discharged, to restore the supply to the amplifier and waveguide. This cycle of operation is repeated should a further arc or arcs occur until the dust, &c. causing the arcing is vaporized. Reference is made to a modified arrangement in which the supply of D.C. power to the amplifier 16 is interrupted when arcing occurs. Should the coupler 21 be arranged on the waveguide, then a probe electrode, Fig. 2 (not shown), is arranged between the coupler and the window 18 of the amplifier, the probe being connected to a detection circuit which provides a signal to operate the switch control circuit shown in Fig. 1 when an arc occurs in the waveguide between the coupler 21 and the amplifier window 18.