Fire and overload protective circuit for high voltage power supplies

Claim 2

A fire and overload protective circuit for a high voltage power supply comprising: monitoring means for sensing the flow of current through said power supply; means constituting a discRiminator associated with said monitoring means detecting the difference between normal power supply operating current and irregular frequency variations in current which are produced in the power supply as a result of external arcing and generating a signal output upon occurrence thereof, and control means actuated by the signal output for turning off the power supply upon the occurrence of fire arcs.

Claim 3

The circuit of claim 1 including means for differentiating in said signal output between low amplitude current produced by fire arcs and high amplitude current pulses produced by snap arcs, and means for disarming said control means upon occurrence of fortuitous high amplitude pulses created by nonrepetitive snap arcs.

Claim 4

The circuit of claim 2 including means to deactivate said means for disarming immediately subsequent to the incidence of each snap arc whereby snap arcs occurring in quick succession will trigger said control means.

Claim 5

The circuit of claim 3 wherein said means for differentiating comprises a voltage divider network including a Zener diode coupled in series with a resistor across said means for detecting.

Claim 6

The circuit of claim 2 wherein said control means includes first relay means for disconnecting the high voltage power supply when the pulses exceed a first predetermined value ordinarily produced by fire arcs, and said means for disarming includes second relay means cooperative with said first relay means and actuated by pulses of a second higher predetermined value produced by snap arcs, said second relay means rendering said first relay means inoperative when said first relay means are actuated by nonrepetitive snap arc pulses, whereby the power supply will be permitted to operate in the presence of high current, relatively short duration snap arcs.

Claim 7

The circuit of claim 5 wherein said second relay means has a shorter pickup time than said first relay means.

Claim 8

The circuit of claim 6 wherein said second relay means disarms said first relay means in the presence of high current, fortuitous snap arcs.

Claim 9

The circuit of claim 7 wherein said first relay means is actuated by the occurrence of a continuous succession of high current snap arcs.

Claim 10

The circuit of claim 7 including means for adjusting the sensitivity of said first relay means.

Claim 11

The circuit of claim 5 including means for signaling an alarm when said first relay means is actuated.

Claim 12

The circuit of claim 5 wherein said second relay means includes an RC network for determining the period of energization of said second relay means.

Claim 13

The circuit of claim 11 wherein each of said relay means is operated by a corresponding independent power supply.

Claim 14

The circuit of claim 5 wherein each of said relay means is triggered by a corresponding silicon controlled rectifier actuated by the signal output.