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Leakage Detector

IP.com Disclosure Number: IPCOM000091416D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Le Vot, M: AUTHOR

Abstract

This circuit detects leakage occurring between a line, fed by a floating voltage supply of 100 volts maximum, and ground. It can be adjusted to open the line for positive or negative leakage currents greater than 30 Mu A. Switching the line off is obtained by two contacts of relay Re driven by an SCR. The line is also opened if one of the supply voltages is missing. Variations of 20% of these voltages have no effect on the detection circuit operation.

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Leakage Detector

This circuit detects leakage occurring between a line, fed by a floating voltage supply of 100 volts maximum, and ground. It can be adjusted to open the line for positive or negative leakage currents greater than 30 Mu A. Switching the line off is obtained by two contacts of relay Re driven by an SCR. The line is also opened if one of the supply voltages is missing. Variations of 20% of these voltages have no effect on the detection circuit operation.

The response time is that of the Re dropout time and can be increased by an optional capacitor at the input. The circuit uses a resistive bridge R1 and R2, the center tap of which is grounded through resistors R3 and R4 in series. The values of R1, R2, and R3 are high and equal. Point A between R3 and R4 is connected to the input of a Darlington circuit including transistors T1 and T2 and resistor R5. The output level of the Darlington circuit drives a symmetrical circuit including transistors T3 and T4, collector load R6, resistors R9 and R10 and cross-connecting connecting paths through R7 and R8. Clamping diodes D1 and D2 are used for symmetry compensation. The output of the symmetrical circuit is connected to the gate of an SCR with resistor R13 between gate and grounded emitter, thus eliminating noise effects. SCR energizes Re closing relay contacts Re 1 and Re 2 on the line and Re 3 on its power supplying circuit. Transistor T5, diode D3, resistors R11 and R12 are used to drive the SCR off whe...