Auxiliary means for completing current transformer secondary winding circuit

Claim 2

In combination with a current transformer having an energized primary winding and a secondary winding having a voltage across its terminals and being connected to a load, said secondary winding being disconnectable from said load, circuit means providing a flow path for current flowing through the secondary winding other than through the load comprising: the secondary winding of the currEnt transformer, said secondary winding having a high voltage level when disconnected from the load, and a semiconductor switch circuit connected alone in series with the secondary winding when the latter is disconnected from the load and being non-conductive while said load is connected to the secondary winding, said semi-conductor switch circuit being conductive in response to said voltage rising toward said high voltage level to conduct current from the secondary winding, said semi-conductor switch circuit having a distinct voltage level thereacross while conducting current, said current having a level determined by the impedance of the secondary winding in series with the switch whereby the product of the voltage and current respectively determined by the semi-conductor switch circuit and the impedance of the secondary winding does not become excessive when the load is disconnected from the secondary winding.

Claim 3

The combination according to claim 1 wherein said semi-conductor switch circuit includes a Zener diode.

Claim 4

The combination according to claim 1 wherein the impedance of said semi-conductor decreases with increased current flow through it and the impedance of the secondary winding increases to said value as the impedance of the semi-conductor decreases.

Claim 5

In combination with a current transformer having an energized primary winding, a voltage regulator circuit comprising: a secondary winding of the current transformer, and semi-conductor switch means connected in circuit with said secondary winding for maintaining the voltage across said secondary winding within a predetermined range, said semi-conductor switch means being conductive only in response to a voltage across its terminals not less than a predetermined distinct level and being in circuit alone with said secondary winding while so conductive, said semi-conductor switch means having an impedance during conduction insufficient to limit current through it to a safe operating level, said secondary winding having an impedance during conduction of said semi-conductor switch means sufficient to limit current through the switch means to a safe level, condition, circuit means providing a flow path for current flowing through the secondary winding other than through the load comprising: the secondary winding of the current transformer, said secondary winding having a high voltage level when said load is in its high impedance condition, and semi-conductor switch means having a constant voltage drop across its terminals while conductive and being connected in circuit with said secondary winding for maintaining the voltage across said secondary winding at a distinct lower level than said high voltage level, said semi-conductor switch means being conductive in response to said voltage rising toward said high voltage level to conduct said current from the secondary winding, said semi-conductor switch means having an impedance during conduction of said switch means insufficient to limit current through it to a safe level, said secondary winding having an impedance during conduction of said switch means sufficient to limit current through the switch means to a safe level.

Claim 6

In combination with a current transformer having an energized primary winding, a voltage regulator circuit comprising: a secondary winding of the current transformer, and semi-conductor switch means connected in circuit with said secondary winding for maintaining the voltage across said secondary winding within a predetermined range, said semi-conductor switch means being conductive only in response to a voltage across its terminals not less than a predetermined distinct level and being in circuit alone with said secondary winding while so conductive, said semi-conductor switch means having an impedance during conduction insufficient to limit current through it to a safe operating level, said secondary winding having an impedance during conduction of said semi-conductor switch means sufficient to limit current through the switch means to a safe level, condition, circuit means providing a flow path for current flowing through the secondary winding other than through the load comprising: the secondary winding of the current transformer, said secondary winding having a high voltage level when said load is in its high impedance condition, and semi-conductor switch means having a constant voltage drop across its terminals while conductive and being connected in circuit with said secondary winding for maintaining the voltage across said secondary winding at a distinct lower level than said high voltage level, said semi-conductor switch means being conductive in response to said voltage rising toward said high voltage level to conduct said current from the secondary winding, said semi-conductor switch means having an impedance during conduction of said switch means insufficient to limit current through it to a safe level, said secondary winding having an impedance during conduction of said switch means sufficient to limit current through the switch means to a safe level.

Claim 7

The combination according to claim 4 wherein said switch means comprises a semi-conductor switch circuit having an impedance varying inversely with the level of current flowing through it.

Claim 8

The combination according to claim 5 wherein said semi-conductor switch circuit includes a Zener diode.

Claim 9

In combination with a current transformer having an energized primary winding, a secondary winding having a voltage across its terminals and a load connected across said terminals and having a high impedance.

Claim 10

In combination with a current transformer having an energized primary winding, a secondary winding having a voltage across its terminals and a load connected across said terminals and having a high impedance.

Claim 11

The combination according to claim 7 wherein said load has an intermediate impedance condition less than said high impedance condition and the secondary winding has said high voltage level when the load is in its intermediate impedance condition.