Abstract: A resettable switching device, e.g. a relay, comprises a fixed contact (18) and a movable contact (28). A solenoid (12) is fixed relative to the fixed contact and a ferromagnetic plunger (20) carries the movable contact. A spring (24) biases the plunger away from the fixed contact so the device is normally open. When the device is set a further ferromagnetic element, e.g. a plunger (22), holds the first plunger (20) in a closed-contact position by magnetic attraction against the action of the spring (24). When a predetermined current condition exists in the solenoid the magnetic attraction between the element and plunger is reduced below the level necessary to hold the plunger so that the movable contact disengages the fixed contact.

Abstract: An electromagnetic regulating device with a movable actuator (42), especially a piston, having an engagement region (44) on an end thereof, and a coil device (34, 36), which is stationary relative to the actuator and which is designed to exert a force on the actuator. The electromagnetic regulating device is provided with permanent magnet means, through which the actuator (42) is held to the coil device (34, 36) in the inactive state of the coil device (34, 36) and wherein when current is applied to the coil device (34, 36), the actuator (42) is released from the coil device (34, 36), overcoming a retaining force of the permanent magnet means.

Abstract: A medium voltage switching device includes an electromagnetic actuation chain and a power supply which provides electric power to the electromagnetic actuation chain. The power supply includes at least a first power supply device which is electrically connected to a medium voltage power distribution line, so as to drain electric power directly from the distribution line, and a second circuit configured to store at least the electric energy drained from the medium voltage power distribution line, and to thereby provide the electromagnetic actuation chain with electric power.

Abstract: An electromagnet system for a switch includes a main magnetic circuit including a magnet yoke and a magnet armature mechanically linked to a contact apparatus. At least one permanent magnet is disposed in the main magnetic circuit for generating a holding force for the magnet armature. A shunt circuit is provided parallel with the main magnetic circuit so that the permanent magnet is a magnetic energy source for the shunt circuit. The shunt circuit includes pole legs and a yoke arc of the magnet yoke. The magnet armature is capable of contacting the pole legs so as to close the shunt circuit. An excitation winding is provided for each of the pole legs for to generating a pull-in force for the magnet armature. The electromagnet system is magnetically dimensioned such that a minimum magnetomotive force of the excitation windings is sufficient for opening the electromagnet system.

Abstract: There is disclosed an electromagnetic relay comprising a stationary first member and a second member adapted to move towards and away from the first member such that when the second member move towards the first member an electrical contact is closed. Spring means biases the members apart, and permanent magnet means are provided for generating a force of attraction between the members, and selectively operable means is provided for generating an electromagnetic force. The permanent magnet means has a strength such that when the first and second members are apart the permanent magnet means is insufficient to overcome the spring means, but when the members are brought together the permanent magnet means is able to hold the members together against the spring means.

Abstract: An electromagnetic regulating device with a movable actuator (42), especially a piston, having an engagement region (44) on an end thereof, and a coil device (34, 36), which is stationary relative to the actuator and which is designed to exert a force on the actuator. The electromagnetic regulating device is provided with permanent magnet means, through which the actuator (42) is held to the coil device (34, 36) in the inactive state of the coil device (34, 36) and wherein when current is applied to the coil device (34, 36), the actuator (42) is released from the coil device (34, 36), overcoming a retaining force of the permanent magnet means.

Abstract: A contactor assembly includes a stationary assembly, a movable assembly that is slidably coupled with the stationary assembly, and a contact assembly coupled within the stationary assembly and the movable assembly. The contact assembly is movable between a first switching position where an electrically closed circuit is established and a second position where an electrically open position is established. The stationary assembly has a solenoid housing that is used to move the movable assembly between the first position and the second position. The solenoid housing may include a first coil and a second coil therein. Further, a pair of magnets is positioned between the solenoid coils and the housing to provide magnetic flux to maintain the contactor in an electrically closed position.

Abstract: An actuator comprises a magnet yoke and a carrier member movable relative to the magnet yoke. The magnet yoke has at least one permanent magnet and the carrier member is positioned in the magnetic field produced by this magnet. The carrier member has an auxiliary magnetic member that produces a relative bias force between the carrier member and the magnet yoke. The bias force will be used to compensate for a weight applied to the device and acts as a bearing with a very large compliance. The carrier member also comprises a coil. Passing current through the coil produces a Lorentz force for further control of the actuator; alternatively, the device provides a velocity transducer by sensing the EMF generated in the coil by relative motion of the carrier member and magnet yoke.

Abstract: A switching device which can be small-sized by improving a shielding performance and can improve the reliability of switching characteristics.

Abstract: A load-disconnecting switch has a permanent-magnetic holding circuit. A coil (5), upon excitation thereof, generates a magnetic flux that is opposite to the magnetic flux of the permanent magnet (9). The armature (6) is biassed to an open position by an armature spring (10), so that the armature spring (10), when a defined operational excitation is exceeded, detaches the armature (6) from the core (7) of the magnet system, allowing said armature to open and thereby disconnecting a switching contact (15) and a fixed contact (16). The load-disconnecting switch can be switched on again by means of a spring clip (12) acting on said armature (6).

Abstract: A bistable contactor comprises at least two concentrically arranged coils, an armature that is movable relative to the coils, a permanent magnet that is stationary relative to the coils, and a spring element. The armature includes contacts for opening and closing a circuit. The coils move the armature and contacts between a first stable position and a second stable position. In the first stable position, the armature is held in position by the permanent magnet, and in the second stable position, the armature is biased into position by the spring element.

Abstract: The invention relates to a microrelay comprising a magnetic spool, a contact support body (2) within which contacts are arranged, a permanent magnet (32) and an armature (31) which is tiltable around it's axis between two positions, as well as a spring-loaded reversing system. The inventive micro relay is characterized in that the magnetic spool system (1) is configured as a flat spool system (1) in the form of a microstructure arranged on a flow plate (11) and is composed of at least one flat microspool (12′). The pivoting armature (31′) can itself be configured in the form of a three pole magnet (32′) or a two pole magnet (32″). The inventive microrelay has a minimal overall height and can be produced in a cost effective way in an automated manufacturing process.

Abstract: A magnetic trip with a fixed magnetic circuit polarised by a permanent magnet. The magnetic circuit includes two preferably identical parallel wafers each defining a main branch and a deflection tab with the presence of a coil on each branch. At their ends opposite to the mobile pallet, the wafers have in cross-section an L shape. The insulation structure carrying the coils is formed of two half-shells tightly holding the wafers. The trip can be used in circuit breakers.

Abstract: A non-explosive actuator includes a housing, a push rod extending into one end of the housing and a plurality of dogs within the housing. A plunger is inserted into an opposite end of the housing and the push rod is depressed and locked in place. Depressing the push rod causes the dogs to engage the plunger and prevent it from being withdrawn from the housing. Unlocking the push rod eventually causes the dogs to release the plunger and allow the plunger to be withdrawn from the housing. The actuator may be reused after the plunger is removed from the housing. The actuator may be reused simply by re-inserting the plunger into the housing and re-depressing the push rod.

Abstract: The invention relates to a magnetic switch having a yoke which has the shape of a rotationally symmetrical cup on the base of which is arranged a permanent magnet. The flux of the permanent magnet is conducted via a core, which has a radial core flange, to the plate-shaped armature. For the operational air gap effective between the armature and the core and the yoke and the magnetic resistance WA thereof, the following relation applies in relation to the marginal air gap formed between the core flange and the yoke: WA<WR. As a result of the rotational symmetry with a yoke having the shape of a cup, it is possible to generate a high holding force for the armature with a small structural volume.

Abstract: An electric appliance control comprising an electromagnet; an electrical switch assembly; a ferromagnetic section movable with a contact of the switch assembly towards the electromagnet; and a user actuated member adapted to move the ferromagnetic section and the contact towards the electromagnet. When the electromagnet is energized and the ferromagnetic section and contact are moved by the user actuated member to an actuated position, the electromagnet can retain the contact at the actuated position by magnetically holding the ferromagnetic section at the actuated position.

Abstract: Electromagnetic actuator for moving a contact into a switched-on or switched-off state, comprising a contact-actuating rod which is displaceable in the longitudinal direction between a first position, corresponding to the switched-off state, and a second position, corresponding to the switched-on state. A core which is made of magnetizable material and interacts with a switch-on coil is attached to the contact-actuating rod. Also present is a pole piece which is made of magnetizable material and of which that face which is directed towards the core, in the first position of the contact-actuating rod, is arranged at an air-gap distance from that surface of the core which is directed perpendicular to the direction of displacement, and in the second position bears as closely as possible against the said core surface. The actuator furthermore comprises a yoke made of magnetizable material for closing the magnetic flux circuit of the switch-on coil through the pole piece and the core.

Abstract: A flux transfer shunt trip actuator has an elongated seat member extending between the legs of a U-shaped magnetically permeable frame member. A plunger is magnetically latched against the seat formed by the seat member in a retracted position by permanent magnets positioned adjacent the seat. The field generated by permanent magnets produces a latching force which exceeds a bias force generated by a helical compression spring extending along the elongated seat member and biasing the plunger toward an actuated position spaced from the seat. A coil surrounding the elongated seat member and the spring, generates an electromagnetic field when energized which bucks the permanent magnet field so that the plunger is driven to the actuated position by the spring. Preload on the spring is adjusted by an adjusting member positioned along a threaded shaft coaxial with the spring and extending from the bight of the U-shaped frame in the opposite direction from the pair of legs of the frame.

Abstract: The present invention relates to a switch with a rocker, which has an affixed magnet, capable of being reliably opened or closed by a mechanical operation of a magnetized rocker. The present invention comprises of a supporting plate and a plurality of electromagnets occurring a magnetic force when a power is supplied thereto and being disposed in a bottom surface of the supporting plate. Further, the present invention has a rocker made of a magnetic substance, magnetized in order to occur repulsion with the electromagnet and then rotated by a predetermined angle. Furthermore, the present invention at least one magnet for magnetizing the rocker and retaining an inclined state of the rocker by the if occurred attraction with the electromagnet, and being disposed on the rocker.

Abstract: An electromagnetic actuator has an iron core around which a coil is wound; two permanent magnets, the same poles of which are placed on the ends of the core which extend beyond the coil and which have the same direction of polarity; magnetic poles formed on either end of the iron core; a yoke which connects the poles of the magnets opposite those which face the core; and an iron armature which is supported by a fulcrum on the yoke in such a way that it is free to rotate around the fulcrum, and which has on either end a magnetic pole which faces one of the poles of the core.

Abstract: A switching apparatus including an electromagnetic command device fitted with a magnetic circuit made up of a main circuit polarized by a permanent magnet and linked to a depolarizing coil and through a movable circuit integral with a movable support subject to a return spring and acting directly or indirectly on at least one disconnecting pole. The main magnetic circuit has at least two air gaps in series on the path of the magnetic flux generated by the permanent magnet and the movable magnetic circuit includes at least two parts capable of closing the air gaps when the main magnetic circuit and the movable magnetic circuit are joined together and are crossed by the magnetic flux created by the permanent magnetic, thereby carrying out a locking function and creating a multiplication of the locking forces, with an unlocking function being provided by the depolarization coil the counter-flux from which crosses the magnetic circuit and air gaps.

Abstract: A switching device providing highly-reliable, frictionless, adjustment-free operation is described. Comprised of a comparatively small number of moving parts, the various aspects of the invention offer compact, cost-effective, reliable alternatives to their complex electromagnetic and costly solid-state counterparts. The main parts of the invention rely upon the principles of magnetic attraction and repulsion for the switching of a plurality of electrical contacts contained within the switching device. The flexibility inherent in the design of the invention permits the switching device to be configured in a variety of aspects, including the failsafe and latching designs described herein.

Abstract: A switch device including an inner yoke and an outer yoke are arranged around the winding of an electromagnetic block, and a plate-shaped permanent magnet is inserted between the two yokes. A highly efficient actuation of the switching device is achieved by the assistance of the permanent magnet.

Abstract: A polarized relay with an electromagnet which consists of an exciter coil and a coil core mounted in the exciter coil. On each of two end sides of the electromagnet is a permanent magnet displaceable along its magnetic axis. The same pole, for example, the north pole (N), of each of the two permanent magnets face the end sides of the electromagnet. The relay is capable of tri-stable behavior, that is, it can switch between three states, with only one exciter coil. Preferably, the tri-stable function of the relay controls a commutator motor between "rest," "clockwise running," and "counter-clockwise running" states.

Abstract: A telephone device for preventing a long-term on-line state resulting from the handset being unintentionally left off-hook.

Abstract: An electromechanical switch including a non-magnetic cup shaped housing, the interior of which is sealed from the atmosphere with a seal assembly. A first electric terminal extends through the seal assembly and is connected to a coil spring. A second terminal includes a stationary electrode. The electrode extends through the seal assembly and through the coil spring. The coil spring supports a movable contact. A permanent magnet is selectively movable via a solenoid in close proximity to the contact member for selectively moving the contact member in and out of contact with electrode. In the closed position, electric current flows between the first and second terminals and through the coil spring. In another embodiment, an electric magnet provides the necessary flux for selectively moving the contact member.

Abstract: A magnetically latching solenoid apparatus is characterized by a non-magnetic armature carrying a permanent magnet having poles aligned with the throw axis of the device. The poles of the magnet are substantially aligned with corresponding pole pieces and define respective variable air gaps therebetween. The apparatus assumes one of two bistable magnetically latched states according to the one of the air gaps across which the magnetic attractive force exceeds the magnetic attractive force across the other of the air gaps. Single or dual winding coils temporally excitable unidirectionally or bidirectionally and, in the case of dual winding coils mutually exclusively or contemporaneously, to cause the latch state to change.

Abstract: A polarized bistable electromagnetic relay arrangement comprising at least two monostable instantaneous electromagnetic relay devices with a L-shaped yoke, a permanent magnet disposed between both relay devices so that one magnetic pole be magnetically connected by polar masses to both yokes of the relay devices and polar masses magnetically connect the other pole of the magnet to both blades whereas the magnetic circuits of both relay devices are designed so that the magnetic flux produced by one energized coil passes in series through both blades while superposing themselves to the magnetic flux produced by the permanent magnet.

Abstract: A nonvolatile programmable switch includes first and second magnetizable conductors having first and second ends, respectively, each of which is a north or south pole. The ends are mounted for relative movement between a first position in which they are in contact and a second position in which they are insulated from each other. The first conductor is permanently magnetized and the second conductor is switchable in response to a magnetic field applied thereto. Programming means are associated with the second conductor for switchably magnetizing the second conductor so that the second end is alternatively a north or south pole. The first and second ends are held in the first position by magnetic attraction and in the second position by magnetic repulsion.

Abstract: An electromagnetic switching device for controlling the flow of electrical current between a plurality of pins. The switching device includes a base, an input pin, first and second output pins, a reed, an actuator, a magnetic field generator, and generator pins. The reed and actuators are movable between a first position which electrically couples the first output pin and the input pin, and a second position which electrically couples the second output pin and the input pin. Dielectric compatible plastic material with enhanced shielding characteristics is located in apertures in the base to structurally retain the pins therein. The actuator further includes a center body portion, an arm integrally molded with the center body portion extending generally laterally outward therefrom, and a finger depending downwardly from the arm. The finger is structurally coupled to the movable reed to move the reed between its first and second positions.

Abstract: The invention is directed to an improved electromagnetic force motor (10) with internal eddy current damping. In the preferred embodiment, the motor is comprised of a body (11), a pair of permanent magnets (15.sub.L, 15.sub.R), an electromagnetic coil (20), and an armature (13). The armature is positioned with respect to the body so as to define two variable-reluctance working air gaps (30, 31) and a constant-reluctance non-working air gap (29). The permanent magnets face one another and are mounted on the body. The body and armature are both adapted to conduct magnetic flux. Each working air gap contains a magnetic flux that is the algebraic sum of a flux attributable to the permanent magnets and a flux attributable to the coil. The non-working air gap contains flux attributable only to the permanent magnets. A current-conducting member (14) is attached to the armature and positioned within the non-working air gap.

Abstract: A method and apparatus for electromechanically locking a docking station to a computer using an electromagnetic attractive force is disclosed. In a preferred embodiment, the docking station includes a latching mechanism with a ferromagnetic handle, and an electromagnet proximately located to the latching mechanism. The latch mechanically secures the docking station to the PC. The electromagnet is positioned such that, when electrically energized, the electromagnetic field produced thereby attracts the handle with sufficient force to prevent the handle from being used to disconnect the PC from the docking station. Alternatively, the electromagnet can be located in the docking station so that it is near a ferromagnetic plate in the PC when the PC is docked.

Abstract: A field-installable circuit breaker trip actuator unit includes a flux shifter unit that interfaces with the circuit breaker operating mechanism and is installable without dismantling the circuit breaker components. The flux shifter unit responds to an electronic trip unit to articulate the circuit breaker operating mechanism and separate the circuit breaker contacts upon occurrence of an overcurrent condition. A reset arrangement allows the trip actuator unit to be automatically reset upon completion of the contact separation process.

Abstract: An electromagnetic switching arrangement for operating a control device, with the arrangement having two electromagnets (1, 2) which are formed respectively from a coil (3.1, 3.2) and a magnetic yoke (4.1, 4.2), are connected to an actuatable direct-current supply (9), and are spaced from one another, with the pole faces (5) of the two magnet yokes (4.1. 4.2) facing one another. An armature (6) is disposed between the two electromagnets so that the armature can move back and forth between the pole faces (5) of the two electromagnets. The armature (6) is connected to the control device to be operated and is held by spring elements (8.1, 8.2) in an inoperative or neutral position between the two electromagnets (1, 2) when both electromagnets are currentless. At least the armature (6) is made of a material that contains a residual magnetization.

Abstract: A field-installable circuit breaker trip actuator unit includes a flux shifter unit that interfaces with the circuit breaker operating mechanism and is installable without dismantling the circuit breaker components. The flux shifter unit responds to an electronic trip unit to articulate the circuit breaker operating mechanism and separate the circuit breaker contacts upon occurrence of an overcurrent condition. A reset arrangement allows the trip actuator unit to be automatically reset upon completion of the contact separation process.

Abstract: An electromagnetic actuator includes an actuator rod having a plurality of magnetic assemblies disposed about a longitudinal axis of the actuator rod. Each plurality of magnetic assemblies develops alternating magnetic flux along the longitudinal axis. The electromagnetic actuator further includes a plurality of stator windings secured to a support structure and disposed about the longitudinal axis. Each stator winding has a pole facing a portion of one of the plurality of magnetic assemblies and the longitudinal axis.

Abstract: A contactor device includes a magnetic latch apparatus to reduce bounce between contact pads on closing. The magnetic latch apparatus includes a first magnet assembly and a second magnet assembly disposed so as to magnetically latch the first contact pad and second contact pad in the closed position. The first and second magnet assemblies typically are disposed respectively on the first contact pad carrier and second contact pad carrier such that the distance between the first and second magnet assemblies corresponds to the distance between the first and second contact pads. The magnet assemblies have a latch element that is a permanent magnet, an electromagnet, or a magnetically attracted material.

Abstract: A flux shifter unit with increased magnetic susceptibility for use with a combined bell alarm and lock-out accessory is connected with the electronic trip unit that controls a high ampere rated circuit breaker. The flux shifter unit is configured to eliminate nuisance tripping due to the vibration of the associated electrical equipment.

Abstract: A magnetic latch for a disk file actuator comprises a latch plate formed of a magnetic material of low magnetic hardness located on the actuator; a core ferromagnetic material of medium magnetic hardness mounted relative to the base and surrounded by a coil. A power supply is selectively coupled to the coil for applying magnetizing/demagnetizing energy to the core. As the latch plate moves in a direction toward the core and a magnetizing force is applied by the power supply, the latch plate becomes drawn to and restrained by the core. When a demagnetizing force is applied to the coil by the power supply, the actuator is released from the latched position.

Abstract: A shunt trip device includes an armature 18 pivotally mounted on a frame 12 of a ferro-magnetic material. A "U"-shaped member 20 is mounted on the frame 12 via a spacer 30 of a non-magnetic material. The member 20 and a portion of a post 16 of the frame 12 and the armature 18 define a first magnetic circuit. A limb 22 and a bridge portion 26 of the member 20 together with a part 14.1 and the post 16 of the frame and the armature 18 define a second magnetic circuit. A limb 24 and the bridge 26 of the member 20 together with the part 14.1 and the post 16 of the frame 12 and that portion of the armature 18 between the post 16 and the limb 24 define a third magnetic circuit. A coil 34 is carried on the limb 22 of the member 20 and permanent magnetic 22 is sandwiched between the portion 26 of the member 20 and the part 14.1 of the frame 12.

Abstract: A disc drive magnetic latch includes a magnet, a bucking coil, and a pair of pole pieces in a housing. The pole pieces have rectangular extension which extend through fingers in the housing thereby locking the pole pieces against rotational movement when a striker on the actuator strikes them. Heat staked tabs hold the assembly together.

Abstract: A shift mechanism for the transmission of a vehicle in which a locking arm is provided to prevent shifting of the shift lever, the locking condition of the locking arm being controlled by a magnetic latch which includes a permanent magnet that produces a magnetic flux to hold the arm in locked position. A coil is provided in the magnetic latch to produce a magnetic flux that opposes the magnetic flux produced by the permanent magnet to destroy the holding force of the permanent magnet when a brake switch is closed to energize the coil thus permitting the locking arm to be moved to an unlocked position and the shift lever to be shifted.

Abstract: A solenoid actuator having a slider element with a permanent magnet is provided. When the electromagnet is activated, the electromagnet repels the permanent magnet, moving the permanent magnet of the slider toward a second position under the influence of a mass of ferro-magnetic material located adjacent the second position. In a preferred embodiment, the poles of the slider permanent magnet are co-axially aligned with the coil and core of the electromagnet. In an alternative embodiment, the mass of ferromagnetic material may be eliminated.

Abstract: To provide the necessary vertical motion of a wire- bonding head (20) mounted on a flexural pivot (16), a wire-bonding machine (10) includes an actuator comprising a permanent magnet (56) mounted on the flexural pivot (16) and extending into the central passage (49) of a ferromagnetic sleeve (46) in which two oppositely wound coils (50 and 52) are mounted. The magnetic force resulting from current flow through the coils (50 and 52) causes the head assembly (18) to pivot about the flexural-pivot axis (16) and thus cause the magnet (56) to move out of symmetry with respect to the ferromagnetic sleeve (46). The resultant attraction between the permanent magnet (56) and the ferromagnetic sleeve (46) tends to counteract the resistance of the flexural pivot (16) to pivotal displacement from a rest position but does not additionally reduce the stiffness of the flexural pivot to other, undesired modes of motion.

Abstract: A magnetic brake provides braking or locking capability and is remotely controlled by electric power. The magnetic brake comprises a rotatable shaft and a brake disc mounted on the shaft. A non-rotating core housing assembly located around the shaft includes a permanent magnet and a bipolar solenoid. A magnetic armature adjacent to the core housing assembly is capable of movement toward the core housing assembly and toward and into engagement with a brake disc to prevent rotation of the shaft. A spring urges the armature away from the core housing assembly and into engagement with the brake disc. The brake does not use any electric power to maintain the brake in the set mode with the rotating shaft fully locked, or in the released mode with the rotating shaft fully released. The permanent magnet is of sufficient strength to hold the armature against urging of the spring until an opposite polarity is supplied by the solenoid.

Abstract: A magnetic valve which is closed when current is absent includes an electromagnet driver having a U-shaped magnetizable yoke carrying a winding; a pivotally attached armature including a soft magnetic material; a permanent magnet disposed on the armature; and a pole plate disposed between the permanent magnet and a part of the yoke which carries the winding. The yoke part and the pole plate define a separating plane therebetween. The mangetic valve further has a valve cone disposed on the armature below the separating plane.

Abstract: Trip device of the suction or pull-in armature type, having a yoke (18; 35) supporting a fixed permanent magnet (22) and a movable elongated armature (23) having a head member (25). The armature (23) and the yoke (18; 35) forming a first magnetic circuit for holding the armature (23) in a first position with the permanent magnet (22), in which first position the head member (25) protrudes outside the yoke (18; 35). For moving the armature (23) electromagnetically and/or electrothermally to a second position in which the head member (25) protrudes further outside the yoke (18; 35), the yoke (18; 35) is provided with electrothermal bimetal device (33; 37).

Abstract: A non-latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes a permanent magnet and an electromagnet. The respective sections are arranged in separate locations or cavities in the assembly. The switch has a "normal" position and is selectively switched by an overriding electromagnetic assembly. The switch returns to the "normal" position when the overriding electromagnetic assembly is inactive.

Abstract: A latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes at least one permanent magnet and at least one electromagnet. The respective sections are, generally, arranged in separate locations or cavities in the assembly. The switch is latched by a permanent magnet assembly and selectively switched by an overriding electromagnetic assembly.

Abstract: An electro-magnetic shunt trip device has a pair of aligned plungers 10,24. A first plunger 19 acts on an operating member 20 which is pivotal and connected to a spring 18. The second plunger 24 is manually displaceable. A further spring 26 is located between the plungers. The plungers are part of a magnetic circuit, with a magnetic field being generated by a permanent magnet 30 and an electro-magnet 32. The permanent magnet and the electro-magnet generate fields of opposite polarity. If there is no current in the electro-magnet, the field provided by the electro-magnet will be sufficiently strong to hold the two plungers together. The spring 18 acting on the operating member will cause it and the plungers to move, so that the operating member is in a non-tripping position.