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US 3,943,473 AGranted
Current limiting circuit breaker
AssigneeSquare D Company
InventorJoseph M. Khalid
Life of this patent
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AssigneeSquare D Company
InventorJoseph M. Khalid
Estimating the term…
A current limiting circuit breaker having for each pole, a pair of main contacts separable upon operation of a thermally and electromagnetically operable tripping device and a pair of auxiliary contacts for current limiting in series with the main contacts and in parallel with a transformable resistor having a positive temperature coefficient of resistance. The auxiliary contacts are separable when an electromagnet is energized by a fault current which simultaneously energizes a field magnet to produce a transverse magnetic field across the auxiliary contacts and the arc formed between them when separating. This simultaneous action of electromagnet and field magnet coacting for rapid contact separation and lengthening of the arc upon flow of a fault current serves to increase arc voltage almost instantaneously to that of the source, about which time the fault current is totally shunted into the resistor.
A current limiting circuit breaker comprising a molded case, a first pair of separable contacts inn the case, thermally and electromagnetically operable tripping means in the case effective upon operation to cause separation of the first pair of contacts, a pair of elongated contact blades pivotally mounted in the case, each of the contact blades having a contact mounted thereon and engaged with the contact on the other of the contact blades when the contact blades are in a closed position, the contacts on the contact blades being a second pair of separable contacts connected in series with the first pair, electromagnetically operable means in the case effective upon operation to cause separation of the contact blades and their contacts, a resistor in the case connected in parallel with the second pair of contacts, the resistor having a resistance transformable from a relatively low value to a relatively high value, an elongated magnetic core structure spanning opposite sides of said contact blades along a substantial current carrying portion thereof including the respective portions at which said contacts are mounted, said magnetic core structure being effective upon operation of the electromagnetically operable means to establish a magnetic field transverse to the direction of contact separation, transverse to the arc therebetween as said contacts separate, and transverse to the direction of current flow in said contact blades, and interconnecting means whereby said contact blades and said magnetic core structure are interconnected to coact and simultaneously urge said contact blades apart and said arc away from said contacts in response to a fault current.
A current limiting circuit breaker comprising a molded case, a first pair of separable contacts in the case, thermally and electromagnetically operable tripping means in the case effective upon operation to cause separation of the first pair of contacts, a pair of contact blades pivotally mounted in the case, each of the contact blades having a contact mounted thereon and engaged with the contact on the other of the contact blades when the contact blades are in a closed position, the contacts on the contact blades being a second pair of separable contacts connected in series with the first pair, electromagnetically operable means in the case effective upon operation to cause separation of the contact blades and their contacts, a resistor in the case connected in parallel with the second pair of contacts, the resistor having a resistance transformable from a relatively low value to a relatively high value, and a magnetic core structure operatively associated with the contact blades and effective upon operation of the electromagnetically operable means to establish a magnetic field which aids in the separation of the contact blades and their contacts, including a conductor turn for the magnetic core structure, the conductor turn being connected in series between the first pair of contacts and the resistor, and a series combination of the conductor turn and the resistor being connected in parallel with the second pair of contacts.
A current limiting circuit breaker comprising a molded case, main contact means therein for opening an alternating current circuit protected by the circuit breaker when a fault occurs in the circuit, and current limiting means including normally closed electromagnetically operated contact separation means in series with said main contact means, coordinated auxiliary arc voltage increasing means operatively associated with said contact separation means, coordinated interconnecting means whereby said contact separation means and said coordinated auxiliary arc voltage increasing means are connected to coact simultaneously for contact separation and arc voltage rise in response to a fault current in said circuit above a preselected value, transformable resistance means in parallel with said electromagnetic contact separation means, said resistance means being transformable from an initial lower value of resistance to a substantially higher value of resistance in response to current flow therein, and wherein said current limiting means is responsive to a fault current in said circuit above a preselected value to limit the fault current before it reaches its maximum growth.
A current limiting circuit breaker having capacity to interrupt an electric circuit connected to an alternating voltage source of up to 600 volts, 60 Hz., comprising first separable contact means to interrupt said circuit, current limiting means, said current limiting means including second separable contact means and contact separation means, said contact separation means including co-ordinated auxiliary arc voltage increasing means operatively associated with said contact separation means, co-ordinated interconnecting means whereby said contact separation means and said co-ordinated auxiliary arc voltage increasing means are associated to co-act simultaneously for contact separation and arc voltage rise in response to a fault current in said circuit above a preselected value, current limiting impedance means associated with said contact separation means, said second contact means being separable by said contact separation means within one-sixteenth cycle of current flow after initiation of a fault current of preselected magnitude to actuate said current limiting means, such rapid separation being of such distance and continuity to enable extinguishing of any arc between such contact means within one-sixteenth cycle of current flow for any fault current up to 100,000 amperes root mean square symmetrical.
A current limiting circuit breaker having capacity to interrupt an electric circuit connected to a 60 Hz. alternating voltage source of up to 600 volts, comprising first separable contact means to interrupt said circuit, current limiting means, said current limiting means including second separable contact means and contact separation means, said contact separation means including co-ordinated auxiliary arc voltage increasing means operatively associated with said contact separation means, co-ordinated interconnecting means whereby said contact separation means and said co-ordinated auxiliary arc voltage increasing means are associated to co-act simultaneously for contact separation and arc voltage rise in response to a fault current in said circuit above a preselected value, current limiting impedance means associated with said contact separation means, said second contact means being separable by said contact separation means within one millisecond after imitiation of a fault current of preselected magnitude to actuate said current limiting means, such rapid separation being of such distance and continuity to enable extinguishing of any arc between such contact means within one millisecond for any fault current up to 100,000 amperes root mean square symmetrical.
An unfused circuit breaker having capacity to interrupt an electric circuit connected to an alternating voltage source of up to 600 volts, 60 Hz., comprising separable contact means to interrupt said circuit and contact separation means, said contact separation means including current limiting means comprising co-ordinated auxiliary arc voltage increasing means operatively associated with said contact separation means, co-ordinated interconnecting means whereby said contact separation means and said co-ordinated auxiliary arc voltage increasing means are associated to co-act for contact separation and arc voltage rise in response to a fault current in said circuit above a preselected value, current limiting impedance means associated with said contact separation means, said contact means being separable by said contact separation means within one-quarter cycle of current flow after initiation of a fault current above a threshold value of 1,000 amperes, such rapid separation being of such distance and continuity to enable said breaker to extinguish any arc between such contact means within at least one-half cycle of current flow for any fault current above said threshhold and up to 100,000 amperes root mean square symmetrical.
An unfused circuit breaker having capacity to interrupt an electric circuit connected to an alternating voltage source of up to 600 volts, comprising separable contact means to interrupt said circuit and contact separation means, said contact separation means including current limiting means comprising co-ordinated auxiliary arc voltage increasing means operatively associated with said contact separation means, co-ordinated interconnecting means whereby said contact separation means and said co-ordinated auxiliary arc voltage increasing means are associated to co-act for contact separation and arc voltage rise in response to a fault current in said circuit above a preselected value, current limiting impedance means associated with said contact separation means, said contact means being separable by said contact separation means within four milliseconds after initiation of a fault current above a threshhold value of 1,000 amperes, such rapid separation being of such distance and continuity to enable said breaker to extinguish any arc between such contact means within at least eight milliseconds for any fault current above said threshhold and up to 100,000 amperes root mean square symmetrical.
Dependencies are inferred from the claim text.