High Speed Contact Driver for Circuit Interruption Device

The advent of a practical solid state current limiting interrupter such as described in U.S. patent application Ser. No. 610,947 filed May 16, 1984 in the name of E.K. Howell has provided a synergistic relationship between the circuit interrupter contacts and the contact operating mechanism. By employing a solid state switch in parallel with the contacts, the current is diverted away from the contacts immediately upon contact separation to substantially reduce the arcing energy and hence essentially eliminate the deleterious arcing effect on the contacts. This in turn allows the contacts to be made much smaller and hence reduces both their thermal and inertial mass. The reduction in the inertial mass in turn allows the contacts to be more rapidly separated and hence allows circuit interruption during the early stages of the current wave form. The lower contact inertial mass allows the use of a bridging contact between a pair of fixed contacts such as described in U.S. Pat. No. 4,598,187, issued July 1, 1986, entitled "Current Limiting Circuit Breaker" in the name of E.K. Howell. The bridging contact arrangement provides for a further reduction in the mass of the contacts such that even more rapid contact separation can be attained and allows the current interruption to occur at the correspondingly earlier stages of the current waveform.

U.S. patent application Ser. No. 814,865, filed Dec. 30, 1985 and entitled "High Speed Contact Driver For Circuit Interruption Device", describes an extremely fast contact driver utilizing a balanced cantilever spring and a pair of spaced parallel conductors arranged to drive a bridging contact away from a pair of fixed contacts. The conductors are spaced within a pair of magnetic plates to enhance the electromagnetic repulsion generated between the conductors when a high current pulse is applied.

The aforementioned Patent Applications are incorporated herein for reference purposes and should be reviewed for a good description of the operation of a solid state switch for circuit interruption as well as for describing the configuration of a bridging contact arrangement. The instant invention is directed toward a high speed contact driver for rapidly separating a bridging contact from a pair of fixed contacts similar to that described in the latter referenced patent application Ser. No. 814,865.

U.S. Pat. No. 3,215,796 in name of Bruno Leisi, discloses the idea of utilizing line current to produce a varying magnetic field arranged around a pair of spaced parallel conductors to induce opposing currents within the conductors to drive the conductors apart and to separate movable contacts from associated fixed contacts.

U.S. Pat. No. 3,168,626 in the name of Richard Patrick, discloses a fuse utilizing the repulsive forces developed by fault currents flowing in opposite directions through closely spaced, parallel fuse links to sever one or both links and thus interrupt the faulted circuit.

U.S. Pat. No. 3,002,065 in the name of John LaTour, Jr., discloses the use of excessive line currents flowing in opposite direction through conductive columns to repulse one of the columns and thus provide a shunt path to protect a meter.

U.S. Pat. No. 1,720,566 in the name of Joseph Pestarini discloses a circuit controlling device which utilizes a magnetic force to enhance the electromagnetic separation of a bridging contact from a pair of fixed contacts.

U.S. Pat. No. 4,039,983 in the names of Claude Terracol et al. discloses a high speed circuit interrupter having both main contacts and arcing contacts. The main contacts employ a bridging contact for operation and the arcing contacts utilize electromagnetic forces to hold the arcing contacts closed for a short period of time after separation of the bridging contact from the main contact.

The purpose of the instant invention is to provide a high speed contact driver arrangement wherein a high current pulse is employed to electromagnetically repulse a pair of conductors serving as a contact carrier for a bridging contact arranged across a pair of contacts within a protected circuit for extremely fast circuit interruption upon command.

The invention comprises a high speed contact driver consisting of a pair of parallel-spaced conductors each comprising an upper and lower link pivotally connected by means of pivot pins. A bridging contact arranged at the ends of the linked conductors is biased into good electrical contact relation with a pair of stationary contacts by means of a pair of tension springs. A pulse of current applied to the link conductors electromagnetically repels the conductors rotating their links about their pivots and rapidly lifting the bridging contact away from the stationary contacts.

FIG. 1 is a front view of the high speed contact driver according to the invention with the contacts in a closed condition;

FIG. 2 is a side sectional view of the contact driver of FIG. 1 depicted in the plane 2-2; and

FIG. 3 is a front view of the high speed contact driver of FIG. 1 with the contacts in an open condition.

The high speed contact driver of the invention is depicted at 10 in FIGS. 1 and 3 wherein a bridging contact 11 is arranged across a pair of fixed contacts 12, 13 formed on the sloped ends of a pair of bar conductors 14, 15. The bar conductors are attached to an insulated support 16 by means of a pair of bolts 17 as indicated. Suitable materials for the insulated support are "Noryl", which is a tradename of General Electric Company for a modified polyphenylene, and "Valox", a registered tradename of General Electric Company for polybutylene terepthalate. The bar conductors 14, 15 comprise tin-plated copper and the fixed contacts 12, 13 can comprise a silver-silver tungsten compound as generally employed for residential and industrial circuit interruption devices. To substantially increase the operating life of both the fixed and bridging contacts, the composition described in U.S. Pat. No. 4,607,148, entitled "Change Of State Contact Material For Electric Circuit Interrupters", can also be employed. When the high speed contact driver is contained within an inert gas or evacuated environment, such as described in U.S. patent application Ser. No. 770,931, filed Aug. 30, 1985 and entitled "Low Voltage Vacuum Circuit Interrupter", the materials for both the fixed and bridging contacts can comprise copper or aluminium. The sloped edges of the bar conductors 14, 15, for example, can comprise the fixed contacts without any silver material required. The bridging contact is attached to one end of a pair of lower links 18, 19 by means of pins 20 and the other ends of the lower links are pivotally attached by pins 23 to a pair of upper links 21, 22. The upper links 21, 22 are in turn pivotally connected with a pair of L-shaped conductors 24, 25 by means of pins 26 and are arranged such that the upper and lower links freely pivot about their pins. The L-shaped conductors are attached to the insulative support by means of bolts 27 to support the upper and lower links as well as to support a transformer 28. The secondary winding of the transformer consists of a crosspiece 30 which connects across the opposite ends of the L-shaped conductors and which is attached thereto by means of the same bolts 27. The primary winding 42 of the transformer is arranged around a torroidal core 43 and is electrically connected with a current source (not shown) by means of primary winding leads 29. A pair of tension springs 31, 32 are attached to the toggle pins 23 at one end and are attached to a pair of supports 38, 39 on opposite sides of the insulative support 16. The distance between bolts 17 and 27 is arranged such that the upper and lower links are slightly bowed away from each other in the vertical plane, as depicted in FIG. 1. This results in a force vector generated by the attached bridging contact 11 on the fixed contacts 12, 13, which is approximately ten times greater than the spring force exerted by springs 31, 32 on the upper and lower links in the horizontal plane, as viewed in FIG. 1. The electromagnetic repulsion force exerted between the upper and lower links, when a current pulse is applied to the transformer, is concentrated in the immediate vicinity of the upper and lower links by means of a pair of upper and lower pole pieces 33, 34. When such a current pulse is applied to the transformer, the upper and lower links are rapidly repulsed to the position indicated in FIG. 3, thereby rapidly driving the bridging contact to the open position, also shown in FIG. 3. The positioning of tension springs 31, 32 at the pivotal points of connection between the upper and lower links, allows the electromagnetic force to operate against a relatively small spring force provided by means of springs 31, 32, while the contact force exerted between the bridging and the fixed contacts is substantially higher. This arrangement improves over the earlier high speed contact driver described within referenced U.S. patent application Ser. No. 814,865 by eliminating the heavy contact spring and the cantilevered mass arrangement described therein.

Referring now to FIG. 2, the high speed contact driver 10 is shown completely contained on the insulative support 16 with the transformer 28 fitted within arcuate recess 44 formed within the support and retained by means of bolts 27, which pass through the L-shaped conductor 24 and the crosspiece 30 on the front of the support and attach thereto by means of nuts 35 on the back side of the support which are arranged within an offset 45 formed within the insulative support. The upper pole pieces 33 comprise a pair of front and back pieces 33A, 33B joined at each end to form a "slot motor", as so defined within the circuit protection industry. The upper pole 33 is held to the front surface of the insulative support and attached thereto by means of bolts 50 and nuts 51. The lower pole pieces 34 comprise a pair of front and back pieces 34A, 34B that are similarly arranged such that the pole 34 is affixed to the front surface of the insulative support. The bridging contact 11 has a U-shaped slot 37 formed therein to facilitate the connection of the lower links 18, 19. As described earlier, the bar conductors, as indicated at 14, are attached to the insulative support by means of bolts 17 extending through the support and attached to the back surface thereof by means of nuts 36.

It is thus shown that a high speed contact driver in accordance with the invention is completely supported by means of an insulative support which completely houses the transformer and the upper and lower links as well as the bar conductors that carry the fixed contacts.