Abstract: A circuit breaker having a magnetic trip assembly includes a load terminal conductor having a first section, a second section, and a transition section connecting the first section and the second section, the transition section having a pair of faces lying in a plane generally perpendicular to a surface of the second section; a current transformer positioned around the second section of the load terminal conductor, the current transformer having a first side positioned generally parallel to the faces of transition section; and an insulating barrier positioned between the first side of the current transformer and the faces of the transition section of the load terminal conductor, the insulating barrier having a generally planar portion and a pair of leg portions extending from one edge of the generally planar portion, each leg portion lying along a side of the second section of the load terminal conductor and having a protrusion positioned adjacent a distal end thereof, each of said protrusions being positione

Abstract: The present invention is directed to an activity book designed to make reading more enjoyable and educational for young readers. The activity book of the present invention comprises at least one illustrated page with at least one opening on the page through which a moldable material such as modeling clay is forced or extruded by the reader as through a die. The moldable material is forced through the opening(s) by the reader compressing the illustrated page against an area located on a hard flat surface such as a table or another page of the book. The moldable material passing through the opening(s) completes the illustration on the page. The shape of the opening(s) compliments the illustration and facilitates the completion of the illustration when a moldable material is extruded through the opening.

Abstract: An electrically conducting strap for use in a rotary circuit breaker cassette provides dual connectors to accommodate either an electronic or mechanical trip unit within the circuit breaker and electrical distribution system. The continuous, integral strap includes a first section including a fixed contact mounted thereon, a U-shaped second section, a third section having two apertures for connection to associated electrical equipment, and a fourth section having two apertures for connection to a line of a distribution system providing electrical power to a load. Thus, the circuit breaker has the advantage of reduced cost and increased ease of manufacturability since a common cassette is used.

Abstract: A movable contact arrangement for a low-voltage circuit breaker which has a contact lever bracket equipped with contact levers and may move around a pivot bearing for opening and closing the circuit breaker. A journal, which engages with a bearing opening close to an inner end of a stationary conductor segment, is molded onto a main arm of the contact lever bracket. The journal is positioned more or less in the center and has a length that does not exceed the width of the contact arrangement. The bearing opening is also positioned within the width of the contact arrangement. This reduces the width of the circuit breaker, especially in multipole designs, while simultaneously improving the load carrying capacity and service life of the pivot bearing.

Abstract: A circuit breaker rotary contact arrangement is disclosed in which the ends of the line and load straps supporting the fixed contacts are hook-shaped to control the angle of the repulsive force exhibited between the fixed contacts and the movable contacts arranged at the opposing ends of the rotary contact arm. The fixed contacts face outwardly away from the central pivot of the contact arm such that a horizontal component of the popping force acts away from the center of rotation keeping the contact arm in tension for avoiding a buckling effect allowing contact arms with smaller cross sectional area to be used to increase contact arm mobility and reduce the cost.

Abstract: A supplemental magnetic trip unit is arranged on the load strap of an industrial-rated circuit breaker to interrupt circuit current upon occurrence of a short circuit fault. The trip unit employs a U-shaped magnet and a hinged armature that articulates the circuit breaker operating mechanism latch to allow the circuit breaker contacts to become separated upon the urgence of the powerful circuit breaker operating mechanism springs.

Abstract: An electrical circuit breaker includes a moveable contact piece connected to an actuating means and provided with a contact face arranged to make contact with a contact face of a second contact piece by movement of the moveable contact piece generally in a first direction. The circuit breaker further includes an electrical connector for conveying current to the moveable contact piece which includes at least two adjacent limbs adapted to convey the current in opposing directions so as to generate an electromagnetic force repelling the adjacent limbs from one another, which force is used to assist in maintaining the contact faces in abutment.

Abstract: A switching contact system of a low-voltage circuit breaker has a bus with cord-like flexible conductors attached thereto. The flexible conductors are accommodated between a connecting surface (30) of the bus (26) and an end piece (27), which is in contact with the connecting surface (30) of the bus (26) with at least two contact surfaces. The parts are connected by heat effect, such as soldering or electron beam welding.

Abstract: A U-shaped magnetic plate is positioned on the side of a movable contact shoe opposite to a fixed contact shoe, and the tips of the respective legs of the magnetic plate face via a gap the movable contact shoe in a closed condition of the movable contact shoe. A magnetic plate is attached to the surface of the movable contact shoe at the side of the fixed contact, so that the magnetic plates form a closed magnetic circuit surrounding the movable contact shoe. If a high current, such as short circuit current, flows, a magnetic flux passing through the closed magnetic circuit induces an attractive force between the upper end surfaces of the U-shaper magnetic plate and the end surface of the magnetic plate. Accordingly, the movable contact shoe is rapidly opened to quickly interrupt the current, before a signal from an overcurrent trip apparatus operates an opening and closing mechanism. The opening speed of the movable contact shoe is increased when high current flows.

Abstract: An electric switch has an arc extinguishing mechanism that includes a plurality of splitter plates located adjacent to the switch contacts. An electromagnet coil is connected between one of the contacts and a splitter plate to produce a magnetic field that drives an arc into the extinguishing mechanism. The unique electromagnet coil is formed by a lamination of a plurality of flat open loops of conductive material alternating with layers of insulation. The flat open loops are interconnected to form a helical coil.

Abstract: A low-voltage circuit breaker has an enclosure with a rear wall and a front part, in which there is a switching contact system with connecting bars. Each of the connecting bars has a web arranged transversally to the longitudinal direction of the connecting bars; the webs are used for contacting the mating surfaces of the rear wall of the enclosure. Fastening means act in the longitudinal direction of the connecting bars.

Abstract: A rotary contact circuit breaker employs a crank to couple a switching mechanism to the rotary contact pole structure. The use of a crank allows for the mechanism and pole structure the individually optimized without effecting the performance of the other. In particular the crank allows for a mechanism that is able to achieve maximum torque delivery to the pole structure.

Abstract: A arcing chamber housing is disclosed for a circuit breaker with a double turning contact breaker. The arcing chamber housing (1) is composed of two housing modules (2, 3) and an extinguishing chamber (19) is arranged in the area of the fixed contact pieces (6, 7) to extinguish the arcs which are formed between the contact pieces of the double turning contact breaker. In order to obtain a arcing chamber housing (1) which is easy and economical to produce, with extinguishing chambers (19) which have a reproducible extinguishing behavior once the arcing chamber is assembled, the two housing modules (2, 3) are substantially L-shaped parts whose inner marginal surfaces (4, 5) face each other. The first parts (17, 18) of the housing, which correspond to the first branches of the L-shaped housing modules (2,3), are designed as extinguishing chambers (19). Also disclosed are the housing modules (2, 3) used to produce such a arcing chamber housing.

Abstract: The circuit breaker is characterized by separable contacts operable between a closed and an open position a contact arm having a latching surface and a latch arranged to engage the latching surface when the contacts are blown-open under short-circuit conditions. The arrangement of the latch allows for a positive lock under high magnitude short circuit levels while minimizing the force required by a mechanism to unlock the arm.

Abstract: A DC contactor has stationary and movable contacts. A magnet is rotatably mounted adjacent to the stationary contact within a self magnetic field produced by the flow of electric current in the stationary contact. The magnet rotates so that its magnetic field extends around the stationary contact in the same direction as the self magnetic field. When an arc forms between the stationary and movable contacts, interaction with the self magnetic field and the magnetic field drives the arc toward an adjacent extinguishing chamber.

Abstract: A contact assembly (22) is adapted for use with a circuit breaker (12) that is set to open a circuit above a predetermined current load. The contact assembly (22) is adapted to reciprocate between a closed position to permit the flow of current through the circuit and an open position to prevent the flow of current. The contact assembly (22) is further adapted to resist unintended reciprocation from the closed position to the open position at current loads up to or exceeding the predetermined current load. The contact assembly includes a line side conductor (38) and a load side conductor (54).

Abstract: The circuit breaker pole or poles comprise a movable contact means with a support carrier movable with respect to the frame between an open position and a closed position and one or more contact fingers movable with respect to the support carrier between a contact position and a retracted position. Electromagnetic compensation means are designed to apply electromagnetic forces on the contact finger or fingers tending to keep the contact finger or fingers in contact with the stationary contact means. Electromagnetic limiting means are designed to apply electromagnetic forces on the contact finger or fingers tending to drive the finger or fingers to their retracted position.

Abstract: A method for retaining a movable contact in a circuit interrupter is applicable to interrupters including first and second contacts, at least one of the contacts being movable. A movable element supporting the movable contact is displaceable between a conducting position wherein the movable contact abuts a cooperating contact to complete a current carrying path through the device, and a non-conducting position wherein the movable contact is electrically separated from the cooperating contact. In accordance with the method, the movable contact is displaced by an interrupt initiation device, and a carrier or retainer is displaced by gas pressure resulting from arcs generated by movement of the contact. The carrier is guided in its displacement within the device housing from a normal operating position to a retaining position. The carrier includes an abutment element that physically contacts the movable element to prevent it from rebounding into contact with the cooperating contact.

Abstract: An integral stationary arcing contact and arc runner for electrical switching apparatus is formed by an electrically conductive member secured to the line conductor adjacent the stationary main contact thereby providing a joint free path for the arc to pass from the arcing contact to the arc runner. Preferably, the electrically conductive member is a sheet metal member having a base section secured to the line conductor, an arcing contact section adjacent the stationary main contact and extending generally perpendicular to the line conductor and a runner section extending at an obtuse angle to the arcing contact section toward the arc chute. A support member between the arcing contact section and the housing transmits reaction forces imposed by the moving conductor assembly on the sheet metal member into the housing.

Abstract: A method an apparatus is disclosed for preventing contact welding during fault conditions. This fault current tolerable contactor includes two magnetic components, one in operable association with the movable contacts, and the other fixable attached above the movable contacts such that when a fault condition occurs, a high magnetic force is created to draw the two magnetic components together thereby opening the contacts. The magnetic force keeps the contacts open at least until current zero, and preferably a defined time thereafter to provide enough time for the contacts to cool and prevent welding upon the closure of the contacts.

Abstract: A circuit breaker having a shunting contact structure with low watts loss and high withstand level. The circuit breaker of the present invention comprises an upper contact arm having a first contact disposed thereon and a lower contact arm having second and third contacts thereon with the second contact mating with the first contact. A shunt terminal is provided between the upper contact arm and the lower contact arm. The shunt terminal includes a fourth contact which mates with the third contact on the lower contact arm. The circuit breaker of the current invention has a closed, open and current limiting position. When the circuit breaker is conducting nominal rated current, the first, second, third and fourth contacts remain closed. When the circuit breaker is under fault conditions which are circuit current conditions above the withstand level, the circuit breaker switches to a current limiting mode.

Abstract: The outside poles of a three pole circuit breaker are each provided with a blow open latch which includes a latch hook having an open slot forming jaws pivotally mounted on the contact arm. A torsion spring biases the jaws to a cocked position in which they are aligned for engagement with a fixed stop member toward which the contact arm rotates as it blows open in response to the magnetic repulsion forces generated by a short circuit. As the jaws engage the stop member, the latch hook is rotated to mechanically latch the latch hook on the stop member thereby preventing rebound and reclosing of the contacts. A leaf spring mounted on the crossbar holds the latch hook in mechanical engagement with the stop member. As the circuit breaker responds to the overcurrent condition and rotates the crossbar, the leaf spring disengages from the latch hook so that the torsion spring can rotate the latch hook back to the cocked position for disengagement from the stop member upon reclosing of the circuit breaker.

Abstract: A switch has at least one fixed and one moving contact located on a contact arm. The fixed contact is connected to a loop-shaped conductor segment, such that when current flows through the conductor segment, there is an electrodynamic magnetic force which acts on the contact arm. The force, above a specified current intensity, results in an opening movement of the contact arm. To open the moving contact more rapidly and in a simple manner the loop-shaped conductor segment is realized so that it is wound in a coil shape, and consists of at least two turns, and that the coil axis of the coil segment runs perpendicular to the longitudinal axis of the contact arm.

Abstract: The helical contact compression springs of a circuit breaker are preassembled in a contact clip for easier assembly of the circuit breaker. The bottom wall of an elongated trough formed by the clip is pierced by holes forming cylindrical protrusions extending into the trough. The clip is placed over the springs supported in a row in a fixture. A die head presses on the spring clip to compress all the springs and then simultaneously insert punches into the holes in the clip to expand the protrusions and secure the springs to the clip. The fixture includes a slide mounted on guides for movement between a loading position and an operating position under the die head. A support block is pivoted on the slide to present one of two sets of spring recesses for circuit breakers having different current ratings with the slide in the loading position.

Abstract: An electric motor control apparatus includes an electrical current control apparatus which is operable to limit current to an electric motor. When the electric motor is a three-phase motor, three current limiting switch assemblies are provided in the electric current control apparatus. A single stack of laminations concentrates magnetic fields emanating from conductors in all three current limiting switch assemblies. Each of the current limiting switch assemblies includes two movable contacts which are mounted on contact arms. The contact arms are movable in slots in the stack of laminations. A first series of splitter plates is disposed in an array along a path of movement of the contact on the first movable contact arm and a second series of splitter plates is disposed along a path of movement of the contact on the second contact arm for each of the current limiting switch assemblies. A short circuit splitter plate conducts electrical current between the two series of splitter plates.

Abstract: A circuit breaker contact arm (56) contains a straight elongate through-slot (112) that runs generally lengthwise of the contact arm and is closed at both lengthwise ends. Adjacent each slot, a respective side wall (106, 108) of a cross bar (58) contains a bent slot (114) having a knee (116). A respective cylindrical blow-open pin (118) passes through all three of these slots. A small helical coiled spring (120) occupies the contact arm through-slot and is compressed between the blow-open pin and the end of the contact arm slot that is proximate a cross bar/contact arm hinge pin (110). The spring is laterally confined by the adjacent side walls of the cross bar so as to remain in the contact arm slot about which the contact arm swings. The spring acts between the blow-open pin and the contact arm to bias the blow-open pin in a direction away from the cross bar/contact arm hinge axis.

Abstract: The helical contact compression springs of a circuit breaker are preassembled in a contact clip for easier assembly of the circuit breaker. The bottom wall of an elongated trough formed by the clip is pierced by holes forming cylindrical protrusions extending into the trough. The clip is placed over the springs supported in a row in a fixture. A die head presses on the spring clip to compress all the springs and then simultaneously insert punches into the holes in the clip to expand the protrusions and secure the springs to the clip. The fixture includes a slide mounted on guides for movement between a loading position and an operating position under the die head. A support block is pivoted on the slide to present one of two sets of spring recesses for circuit breakers having different current ratings with the slide in the loading position.

Abstract: A circuit breaker mechanism has a contact arm (56) forming a portion of an interruptable load current path through the circuit breaker and mounted with respect to a pivot (110) for swinging motion to break the current path. A spring-loaded, over-center operating mechanism includes a toggle mechanism having an upper toggle (74) and a lower toggle (122) coupled by a spring pin (128) to form a toggle joint about which the toggles can relatively pivot. The spring pin has a circular groove (128b) at which it operatively connects to the toggle joint, and a circular surface (128a) adjacent the groove is disposed in the path of travel of the contact arm as the contact arm swings to break the current path.

Abstract: A current-limiting apparatus for a circuit breaker which makes it possible to effectively protect an electric load element by quickly blocking an electric flow path when an excessive current flows due to a ground, shortage, etc. at an electric flow path and preventing a re-formation of an electric flow path after the electric flow path is blocked.

Abstract: A DC circuit breaking device is provided for interrupting the transmission of direct currents to an electric power system by making external changes to an arc generated upon contacting or separation of contacts 11 and 12 in order to rapidly extend and vibrate arc currents. In a self-excited commuting DC circuit breaking device, coils 41 and 42 opposed to a fixed and a movable contact 11 and 12, respectively, are disposed around the outer circumferences of the contacts 11 and 12, and currents flowing through a commutation circuit or the contacts 11 and 12 are allowed to flow through the opposed coils 41 and 42 so as to apply magnetic fields to the neighborhood of an arc. This constitution provides the DC circuit breaking device with high performance that it can rapidly extend and vibrate arc currents to thereby interrupt direct currents.

Abstract: A molded-case multicircuit breaker which suffers insufficient contact pressure at no poles and which is free from damage. The molded-case multicircuit breaker having at least two circuits comprises a handle which performs on-off operation of the circuits simultaneously, a first finger having a movable contact for a first circuit, and another finger having a movable contact for a circuit other than the first circuit, wherein the first finger is designed to be switched on and off directly by the handle, and the finger for a circuit other than the first circuit is electrically insulated from the first finger and is attached resiliently to the first finger. The second finger may be pivotally attached or spring loaded to the first finger.

Abstract: A contact enforcement apparatus for an electric switch includes two electro-magnetic bars. The first electro-magnetic bar is disposed between a crossbar of the switch and a moveable contact arm. The crossbar carries the moveable contact arm and the first electro-magnetic bar such that the electrical contacts of a stationary contact arm and the moveable contact arm are opened and closed by the crossbar. The second electro-magnetic bar is in U-shape and has a front wall and a back wall, between which the moveable contact arm is at least partially inserted when the electrical contacts are closed together. When a "fault" current passes by the electrical contacts, an attractive force between the electro-magnetic bars is largely increased. This attractive force overcomes a repulsive force caused by the "fault" current which tends to open up the electrical contacts, so that the contact between the moveable and stationary contacts remain closed.

Abstract: There is provided an acr extinguishing device of a circuit breaker which closes and opens an electric line, one of two contact parts being fixed to a base part. The arc extinguishing device includes an arc runner formed of an electrically conductive member and arranged on an outer circumference of the above one of the two contact parts. The arc extinguishing device moves, to the arc runner, an arc occurring when a contact made by the two contact parts is opened whereby the arc is extinguished. The arc runner has a cylindrical shape and includes a rising portion formed on an entire inner circumference of the cylindrical shape. A slant angle of the rising portion obtained on a depth side thereof is greater than another slant angle thereof obtained on a front side thereof.

Abstract: A contactor for switching electric current has a stationary contact and a movable contact which when driven by a solenoid moves into and away from abutment with the stationary contact. An arc extinguishing chamber is adjacent to the movable and stationary contacts and includes two rows of splitter plates with a gap therebetween. Each row comprises alternating splitter plates of first and second types. The first type of splitter plate has a first member of non-magnetic material with an aperture within which a permanent magnet is received and a second member of a magnetic material abutting the first member remote from the gap. An outer casing of a non-ferrous, electrically conductive material extends at least partially around the first and second members. The second type of splitter plates are formed of non-ferrous, electrically conductive material. The magnets produce a magnetic field around each of the first type of splitter plates which causes the electric arc to move about the surface of the outer casing.

Abstract: A mechanism for a multipole circuit breaker with high currents and high electrodynamic strength, comprising a toggle device associated to a trip hook and a switching bar, an opening ratchet cooperating with the hook to perform loading and tripping of the mechanism respectively in the locked or unlocked position of the ratchet. The opening ratchet comprises a disengageable actuator causing self-unlocking of the catch in the presence of a short-circuit current exceeding a calibration threshold defined by a flexible element, said self-unlocking being commanded from a mechanical reaction generated by the electrodynamic compensation effect and causing an ultra-fast rotation of the catch to unlock the opening ratchet before the tripping component operates.

Abstract: A thick solid steel slot motor is disposed adjacent a movable conductor to apply a contact closing force on the conductor, augmenting the contact pressure spring, under steady state current conditions, and to reduce the force under high rate of current rise conditions to enhance dynamic separation of the movable conductor from a stationary conductor, reducing the strength requirement of the contact pressure spring.

Abstract: A circuit breaker includes a first section and a second section with independently operating pairs of contact assemblies in each respective section. In the first section, at least one of the contact assemblies is constructed and arranged to interrupt the current by moving from a normally closed position to a blown-open position and latching with the contact assemblies separated. The second section has a biasing extension spring for biasing the contact assemblies of the second section so as to permit interruption of the current in response to a blow-open force, which causes the contacts to separate only momentarily and then return to a normally closed position. The first and second pairs of contact assemblies separate substantially simultaneously in response to the blow-open force, and only the first section reacts to lower-level over-current conditions. In addition to the contact assemblies, the second section of the circuit breaker is designed to operate using only a spring which is "Z-axis" mountable.

Abstract: A circuit breaker including a base having an operating mechanism mounted thereon, a line contact blade assembly coupled to the operating mechanism for movement between open and closed positions, and a load contact blade assembly pivotally supported by a terminal strap for movement between an open and closed position with respect to the line contact blade is disclosed herein. A load blade return spring is positioned to bias the load contact blade assembly into engagement with the line contact blade. Furthermore, a multi-force spring device is disposed to apply a first force to the load contact blade while the load contact blade is in the closed position and a second force to the load contact blade in the blow open position, wherein the first force is greater than the second force.

Abstract: The protective device for protecting against over currents in electric circuits includes at least one electrically conductive body and two electrodes which function to supply circuit current through the conductive body and which lie against the conductive body at corresponding positions either directly or through the medium of an intermediate part. An abutment pressure is applied to the electrode so that the electrodes are maintained in abutment at the corresponding positions of the conductive body. When the devices are subjected to high short circuiting currents, the current density in the deformed abutment surfaces of the conductive body will increase, thus increasing the resistance of the device.

Abstract: A circuit breaker has an electrically conductive blow open latch which forms part of the power circuit so that only short flexible shunts are needed between the latch and trip mechanism. Load current can be conducted from the contact arm to the electrically conductive latch solely through the interface between the latch and the blow open camming surface on the contact arm, and/or through additional short flexible shunts between the latch and the contact arm, preferably adjacent the pivot of the contact arm.

Abstract: A switch having at least one power switching pole includes a contact bridge cooperating with fixed contacts and adapted to be maneuvered either by mobile parts of a solenoid or by a tripping mechanism. The contact bridge is rotatable and the mobile parts of the solenoid operate the contact bridge through the intermediary of a transmission mechanism.

Abstract: A subframe is coaxially pivotally mounted with a movable frame of the operating mechanism of a molded case circuit breaker and is locked to the frame by a bell crank pawl which is pivotally mounted on the subframe. A leaf spring assembly rigidly attached to the subframe overlies the movable contact finger to engage the same in the circuit ON condition of the circuit breaker to provide desired contact force. The bell crank pawl is released upon an incrementally small amount of initial movement of the movable contact arm in response to blow-open magnetic repulsion forces to release the movable contact finger for pivotal opening movement relative to the movable frame of the circuit breaker operating mechanism.

Abstract: An improved circuit breaker with moving line and load contacts is disclosed herein. The circuit breaker includes an enclosure for the operational components thereof including a line contact arm and associated contact for each phase of the circuit breaker, and an operating mechanism supported within the enclosure to move the contact arm(s) between open and closed positions. The circuit breaker also includes a terminal for each phase pivotally supported within the enclosure, and a load contact arm and associated contact for each phase pivotally connected to the terminal. The contact arms are supported so the contacts are engaged when the line contact arms are in the closed positions. The pivoted load terminal(s) allow the use of multiple connector types with the terminal(s), and the pivoting connection between the load contact arm and associated terminal facilitates a reduction in circuit breaker size for a given rating.

Abstract: A multipole circuit breaker having a movable contact for each pole, the movable contact being biased by a spirally-wound spring including a feeler part which slides on a bearing surface of the movable contact to modify the application point of a pressure force P in a second active repulsion position, resulting in a decrease of the restoring torque before operation of the mechanism. The movable contact is forked-shaped and is articulated on an eccentric spindle parallel to the rotation axis of the bar. The spirally-wound spring is mounted to float in the recess of the bar, and comprises two helicoidal wire windings.

Abstract: A self-contained current limiter unit allows lower short-circuit-rated circuit breakers to be utilized within industrial applications. The unit is electrically-connected in series with the circuit breakers and the protected load to limit the short circuit current to a fixed predetermined value while the circuit breaker trip unit responds to interrupt the circuit current. A single unit can be arranged in electrical series connection with a plurality of lower short-circuit-rated circuit breakers to allow a substantial savings in component and equipment costs.

Abstract: A blow-off terminal includes a flat conductive tang, a flat conductive input section, and a flat conductive output section. The input section includes a pair of generally parallel U-shaped strips. Each of the pair of strips includes first and second end portions and a center portion bridging the first and second end portions. The first and second end portions and the center portion of each of the pair of strips are generally co-planar, and the tang and the output section are generally co-planar. The output section is elongated and includes first and second ends, the first end being disposed closer to the tang than the second end. The first end portions of the strips are connected perpendicular to opposite sides of the tang, and the second end portions are connected perpendicular to opposite sides of the second end of the output section. A stationary contact is mounted to the surface of the output section.

Abstract: A repulsion type circuit breaker movable contact device comprising a first movable contact, an opening/closing mechanism which drives the first movable contact for opening and closing, a second movable contact for contacting the first movable contact, the second movable contact being freely pivotable and adapted to receive an electromagnetic repulsion force from said first movable contact, and a contact spring comprising a twisted coil spring disposed with its twisting fulcrum displaced from the rotational pivot of the second movable contact, the contact spring urging the second movable contact into contact with the first movable contact, whereby upon flow of a predetermined mount of electric current through the first and second movable contacts, the electromagnetic repulsion force moves the second movable contact apart from the first movable contact.