Current transformer

Claim 2

In a current transformer having a core adapted to receive a current carrying conductor in linking relation therewith, and having flux responsive output winding means on said core for providing an alternating current output indicative of the current in said conductor, a direct current flux bucking winding for said transformer, a direct current source coupled only to said bucking winding to provide a flux in opposition to flux produced in said core by direct current flowing in said conductor, and coupling means separate from said current transformer for combining the alternating current output produced in said bucking winding with the alternating current output produced in said output winding means.

Claim 3

The apparatus according to claim 1 wherein said means for coupling includes a capacitor interposed between said bucking winding and said output winding means and direct coupling means for connecting said bucking winding to said source of direct current.

Claim 4

The apparatus according to claim 2 wherein said direct coupling means includes a resistor.

Claim 5

The apparatus according to claim 1 wherein said means for coupling includes common flux responsive means linked by winding loops respectively coupled to said output winding means and said bucking winding.

Claim 6

The apparatus according to claim 1 wherein said means for coupling includes means for summing the currents from said output winding means and said bucking winding.

Claim 7

The apparatus according to claim 1 wherein said means for coupling includes a common impedance means for receiving current from said output winding means and said bucking winding.

Claim 8

The apparatus according to claim 1 further including a transformer between said output winding means and said coupling means, said transformer having a turns ratio for providing a reduced current at said means for coupling, said bucking winding bearing the same turns ratio with respect to said output winding means.

Claim 9

A current probe comprising: a fixed portion and a movable portion, said fixed portion carrying a fixed core portion and said movable portion carrying a movable core portion adapted for juxtaposition with the fixed core portion to form a magnetic circuit around an input conductor adapted to be received in an aperture then formed between said fixed and movable core portions, said fixed core portion having flux responsive output winding means on said core for providing an output indicative of current in said input conductor, a direct current flux bucking winding receivable in linking relation with said fixed core portion, with said winding passing through the aperture between said core portions, direct current means for supplying a direct current only to said bucking winding for providing a flux in opposition to flux produced in said core by a direct current flowing in said input conductor, and coupling means separate from said magnetic circuit for coupling said bucking winding with said output winding means and providing a combined alternating current output from said output winding means and said bucking winding.

Claim 10

A current probe comprising: a fixed portion and a movable portion, said fixed portion carrying a fixed core portion and said movable portion carrying a movable core portion adapted for juxtaposition with the fixed core portion to form a magnetic circuit around an input conductor adapted to be received in an aperture then formed between said fixed and movable core portions, said fixed core portion having flux responsive output winding means on said core for providing an output indicative of current in said input conductor, a direct current flux bucking winding receivable in linking relation with said fixed core portion, with said winding passing through the aperture between said core portions, direct current means for supplying a direct current only to said bucking winding for providing a flux in opposition to flux produced in said core by a direct current flowing in said input conductor, and coupling means separate from said magnetic circuit for coupling said bucking winding with said output winding means and providing a combined alternating current output from said output winding means and said bucking winding.

Claim 11

The probe according to claim 8 wherein said bucking winding is removably receivable upon said fixed portion of said probe in linking relation with said fixed core portion.

Claim 12

The probe according to claim 9 wherein said coupling means is selectively removable from such coupling relation.

Claim 13

A current probe comprising: a fixed portion and a movable portion, said fixed portion carrying a fixed core portion and said movable portion carrying a movable core portion adapted for juxtaposition with the fixed core portion to form a magnetic circuit around an input conductor adapted to be received in an aperture then formed between said fIxed and movable core portions, said fixed core portion having flux responsive output winding means cooperating therewith for providing an output indicative of current in said input conductor, a direct current flux bucking winding receivable in linking relation with said fixed core portion, with said winding passing through the aperture between said core portions, direct current coupling means for supplying a direct current to said bucking winding for providing a flux in opposition to predetermined flux as would be caused to exist in said core by a predetermined direct current flowing in said input conductor, and means for coupling said bucking winding in common with said output winding means to provide a combined alternating current output from said output winding means and said bucking winding, said means for coupling comprising loops connected respectively to said bucking winding and said output winding means, and a common flux coupled measuring device linked by both said loops.

Claim 14

A current probe comprising: a fixed portion and a movable portion, said fixed portion carrying a fixed core portion and said movable portion carrying a movable core portion adapted for juxtaposition with the fixed core portion to form a magnetic circuit around an input conductor adapted to be received in an aperture then formed between said fIxed and movable core portions, said fixed core portion having flux responsive output winding means cooperating therewith for providing an output indicative of current in said input conductor, a direct current flux bucking winding receivable in linking relation with said fixed core portion, with said winding passing through the aperture between said core portions, direct current coupling means for supplying a direct current to said bucking winding for providing a flux in opposition to predetermined flux as would be caused to exist in said core by a predetermined direct current flowing in said input conductor, and means for coupling said bucking winding in common with said output winding means to provide a combined alternating current output from said output winding means and said bucking winding, said means for coupling comprising loops connected respectively to said bucking winding and said output winding means, and a common flux coupled measuring device linked by both said loops.

Claim 15

The probe according to claim 11 further including transformer means between said output winding means and the loop connected thereto, such transformer having a turns ratio wherein the larger number of turns is connected to said loop, the bucking winding having a turns ratio with respect to each output winding means which is equal to the turns ratio of said transformer.

Claim 16

The probe according to claim 12 wherein said output winding means comprises a pair of output windings each having an equal number of turns and located respectively on parallel legs of said fixed core portion.

Claim 17

The transformer of claim 1 wherein said output winding means includes a plurality of separate windings connected in parallel and said bucking winding is removable from said core.