Filter-control circuit

Claim 2

In an electrical poweR supply system a filter-control circuit for connection to a DC power source having a circuit breaker connected therewith and to a high current load, said filtercontrol circuit comprising: a pair of input terminals for connection to the DC power source; a pair of output terminals for connection to the high current load; a pair of leads, each of said leads interconnecting separate terminals of each of the pairs of input and output terminals; a first series circuit including a resistor and a filter capacitor connected across the pair of leads; switching circuit means connected across said pair of leads and in a parallel circuit arrangement with said first series circuit, the switching circuit means including a relay having a first normally open contact pair connected across said resistor, so that when said circuit breaker is closed and said filter capacitor is charged to a preset voltage level said switching circuit bypasses said resistor and in case of breakdown in said capacitor, said switching circuit operates to remove the bypass around said resistor before the circuit breaker can open, and time delay means connected in series with the coil of said relay, a second normally open contact pair of said relay being connected across said time delay means.

Claim 3

A filter-control circuit as set forth in claim 1 wherein: said switching circuit has a switching time in the order of at least three times the resistance-capacitance time constant of said first series circuit and less than the operate time of the circuit breaker.

Claim 4

A filter-control circuit as set forth in claim 1 wherein: said relay coil has a resistance of in the order of at least ten times the resistance of said resistor.

Claim 5

A filter-control circuit as set forth in claim 1 including: a normally closed relay contact pair connected to one of said leads for applying a signal to an alarm circuit when said relay is deenergized.

Claim 6

A filter-control circuit as set forth in claim 4 including: a third series circuit including an inductor connected in series between a power terminal and a connection of said first series circuit to the lead connected to that power terminal.

Claim 7

In an electrical power supply system including a DC power source having a circuit breaker connected in series therewith for driving a high current load, a filter control circuit for interconnecting said power source and said high current load comprising: a pair of input terminals for connection to the DC power source; a pair of output terminals for connection to the high current load; a pair of leads, each of said leads interconnecting separate terminals of each of the pairs of input and output terminals; a first series circuit including a resistor and a filter capacitor cconnected across the pair of leads; a parallel circuit arrangement with said first series circuit and including a switching circuit including a relay with a coil having a resistance the magnitude of which is in the order of at least ten times the resistance of said resistor, wherein the operate time of the relay is in the order of at least three times the time constant of said first series circuit, wherein the release time of said relay is faster than the operate time of said circuit breaker, the arrangement being such that when said circuit breaker is closed and said filter capacitor is charged to a preset voltage level said relay is operated to bypass said resistor and in case of breakdown of said capacitor, said relay switches to remove the bypass from the resistor before the circuit can operate; time delay means connected in series with the coil of said relay, and circuit means for connecting a normally open contact pair of said relay across said time delay means.

Claim 8

In an electrical power supply system including a DC power source having a circuit breaker connected in series therewith for driving a high current load, a filter control circuit for interconnecting said power source and said high current load comprising: a pair of input terminals for connection to the DC power source; a pair of output terminals for connection to the high current load; a pair of leads, each of said leads interconnecting separate terminals of each of the pairs of input and output terminals; a first series circuit including a resistor and a filter capacitor cconnected across the pair of leads; a parallel circuit arrangement with said first series circuit and including a switching circuit including a relay with a coil having a resistance the magnitude of which is in the order of at least ten times the resistance of said resistor, wherein the operate time of the relay is in the order of at least three times the time constant of said first series circuit, wherein the release time of said relay is faster than the operate time of said circuit breaker, the arrangement being such that when said circuit breaker is closed and said filter capacitor is charged to a preset voltage level said relay is operated to bypass said resistor and in case of breakdown of said capacitor, said relay switches to remove the bypass from the resistor before the circuit can operate; time delay means connected in series with the coil of said relay, and circuit means for connecting a normally open contact pair of said relay across said time delay means.

Claim 9

The electrical power supply system of claim 6 including: an inductor connected in series with the circuit breaker between the circuit breaker and the connection of the first series circuit to said lead.

Claim 10

THe electrical power supply system of claim 6 wherein the time delay means comprises a thermistor.

Claim 11

The electrical power supply system of claim 1 wherein the time delay means comprises a thermistor.