Saturable reactor limiter for current

Claim 1

A device for limiting current in an electric circuit branch comprising: A. at least three magnetic circuit branch elements extending between two nodes: i. the first of said branch elements being characterized by a permeance P 1 , ii. the second of said branch elements being characterized by a non-linear permeance P 2 and having saturated and non-saturated states, wherein P 2 is greater when said second element is in said non-saturated state than when in said saturated state, and wherein the magnetic flux density of said second element is equal to a saturation flux density which is relatively invariant with respect to magneto-motive force applied across said second element when in said saturated state, and said magnetic flux density is less than said saturated flux density otherwise, iii. the third of said branch elements is characterized by a permeance P 3 and includes a magneto-motive force (mmf) bias means for establishing a bias magnetic flux density in said third element, and includes means for sensing the level of said current and for generating a control signal representative thereof, and wherein said mmf bias means is responsive to said control signal to establish said bias mmf on said third element, the magnitude of said established mmf being a predetermined function of the level of said current, and B. an input coil including means for electrically coupling said device to said electric circuit branch so that said current passes therethrough, said coil having a plurality of windings extending about said second element so that mmf is induced on said second element is response to said current, wherein said elements are magnetically coupled to said nodes, and P 1 is relatively high with respect to the medium external to said device, P 2 is greater than P 1 and is relatively high with respect to the medium external to said device when said second element is non-saturated, and P 3 is relatively low with respect to P 1 and P 2 when said second element is non-saturated, and wherein further the net magnetic flux density in said second element is equal to the saturation flux density for said second element when said current is below a predetermined threshold, and said net flux density is below said saturation flux density when said current is in a predetermined range above and extending from said threshold.

Claim 2

A device for limiting current in an electric circuit branch comprising: A. at least three magnetic circuit branch elements extending between two nodes: i. the first of said branch elements being characterized by a permeance P 1 , ii. the second of said branch elements being characterized by a non-linear permeance P 2 and having saturated and non-saturated states, wherein P 2 is greater when said second element is in said non-saturated state than when in said saturated state, and wherein the magnetic flux density of said second element is equal to a saturation flux density which is relatively invariant with respect to magneto-motive force applied across said second element when in said saturated state, and said magnetic flux density is less than said saturated flux density otherwise, iii. the third of said branch elements is characterized by a permeance P 3 and includes a magneto-motive force (mmf) bias means for establishing a bias magnetic flux density in said third element, and includes means for sensing the level of said current and for generating a control signal representative thereof, and wherein said mmf bias means is responsive to said control signal to establish said bias mmf on said third element, the magnitude of said established mmf being a predetermined function of the level of said current, and B. an input coil including means for electrically coupling said device to said electric circuit branch so that said current passes therethrough, said coil having a plurality of windings extending about said second element so that mmf is induced on said second element is response to said current, wherein said elements are magnetically coupled to said nodes, and P 1 is relatively high with respect to the medium external to said device, P 2 is greater than P 1 and is relatively high with respect to the medium external to said device when said second element is non-saturated, and P 3 is relatively low with respect to P 1 and P 2 when said second element is non-saturated, and wherein further the net magnetic flux density in said second element is equal to the saturation flux density for said second element when said current is below a predetermined threshold, and said net flux density is below said saturation flux density when said current is in a predetermined range above and extending from said threshold.

Claim 12

A device for limiting current in an electric circuit comprising: A. one or more input legs of magnetically saturable material, each input leg having an associated input coil wound around said input leg and coupled to said electric circuit, B. a shunt leg in flux transfer relationship to said input legs, said shunt leg providing a flux shunting path for said input legs, and C. flux bias means for biasing said input legs into saturation when no current passes through said input coils, said bias means including a means to sense level of said current and a means responsive to said sensed level to bias said input legs with an mmf which is related to said level, wherein each of said input coils is adapted to drive its associated input leg out of saturation in response to current from said electric circuit when that current exceeds a predetermined threshold, said associated input leg being saturated when current passing through said input coil is below said threshold.

Claim 13

A device for limiting current in an electric circuit comprising: A. one or more input legs of magnetically saturable material, each input leg having an associated input coil wound around said input leg and coupled to said electric circuit, B. a shunt leg in flux transfer relationship to said input legs, said shunt leg providing a flux shunting path for said input legs, and C. flux bias means for biasing said input legs into saturation when no current passes through said input coils, said bias means including a means to sense level of said current and a means responsive to said sensed level to bias said input legs with an mmf which is related to said level, wherein each of said input coils is adapted to drive its associated input leg out of saturation in response to current from said electric circuit when that current exceeds a predetermined threshold, said associated input leg being saturated when current passing through said input coil is below said threshold.

Claim 14

A device for limiting positive or negative current transients in any electric circuit branch comprising: an input circuit means and an associated direct current limiter, said input circuit means including: a first terminal pair and associated means coupled to said electric circuit branch to provide a signal representative of the magnitude of current therethrough, and a second terminal pair and associated means responsive to said signal to provide a unidirectional current in a predetermined direction through a load coupled across said second terminal pair, wherein the magnitude of said unidirectional current is proportional to the magnitude of the current through said electric circuit branch, and said direct current limiter including: at least three magnetic circuit branch elements extending between two nodes: i. the first of said branch elements being characterized by a permeance P 1 , ii. the second of said branch elements being characterized by a non-linear permeance P 2 and having saturated and non-saturated states, wherein P 2 is greater when said second element is in said non-saturated state than when in said saturated state, and wherein the magnetic flux density of said second element is equal to a saturation flux density which is relatively invariant with respect to magneto-motive force applied across said pg,19 second element when in said saturated state, and said magnetic flux density is less than said saturated flux density otherwise, iii. the third of said branch elements is characterized by a permeance P 3 and includes a magneto-motive force (mmf) bias means for establishing a bias in said third element, and said input circuit load, said load including an input coil having a plurality of windings about said second element so that mmf is induced on said second element in a predetermined direction between said nodes in response to said unidirectional current passing therethrough, wherein said elements are magnetically coupled at said nodes, and P 1 is relatively high with respect to the medium external to said device, P 2 is greater than P 1 and is relatively high with respect to the medium external to said device when said second element is non-saturated, and P 3 is relatively low with respect to P 1 and P 2 when said second element is non-saturated, and wherein further the net magnetic flux density in said second element is equal to the saturation flux density when said unidirectional current is below a predetermined threshold, and said net flux density is below said saturation flux density when said unidirectional current is in a predetermined range above and extending from said threshold.

Claim 15

A device for limiting positive or negative current transients in any electric circuit branch comprising: an input circuit means and an associated direct current limiter, said input circuit means including: a first terminal pair and associated means coupled to said electric circuit branch to provide a signal representative of the magnitude of current therethrough, and a second terminal pair and associated means responsive to said signal to provide a unidirectional current in a predetermined direction through a load coupled across said second terminal pair, wherein the magnitude of said unidirectional current is proportional to the magnitude of the current through said electric circuit branch, and said direct current limiter including: at least three magnetic circuit branch elements extending between two nodes: i. the first of said branch elements being characterized by a permeance P 1 , ii. the second of said branch elements being characterized by a non-linear permeance P 2 and having saturated and non-saturated states, wherein P 2 is greater when said second element is in said non-saturated state than when in said saturated state, and wherein the magnetic flux density of said second element is equal to a saturation flux density which is relatively invariant with respect to magneto-motive force applied across said pg,19 second element when in said saturated state, and said magnetic flux density is less than said saturated flux density otherwise, iii. the third of said branch elements is characterized by a permeance P 3 and includes a magneto-motive force (mmf) bias means for establishing a bias in said third element, and said input circuit load, said load including an input coil having a plurality of windings about said second element so that mmf is induced on said second element in a predetermined direction between said nodes in response to said unidirectional current passing therethrough, wherein said elements are magnetically coupled at said nodes, and P 1 is relatively high with respect to the medium external to said device, P 2 is greater than P 1 and is relatively high with respect to the medium external to said device when said second element is non-saturated, and P 3 is relatively low with respect to P 1 and P 2 when said second element is non-saturated, and wherein further the net magnetic flux density in said second element is equal to the saturation flux density when said unidirectional current is below a predetermined threshold, and said net flux density is below said saturation flux density when said unidirectional current is in a predetermined range above and extending from said threshold.