US3629747A

US3629747A - Electromagnetic trip device for circuit interrupters

Info

Publication number: US3629747A
Application number: US22915A
Authority: US
Inventors: Joseph D Findley Jr
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1970-03-26
Filing date: 1970-03-26
Publication date: 1971-12-21
Anticipated expiration: 1988-12-21
Also published as: JPS463785A; JPS5117707B1

Abstract

An electromagnetic trip device for a circuit interrupter or circuit breaker comprising an electrically conducting substantially nonmagnetic tube having a relatively large number of conductor turns of an energizing coil wound thereon. A stationary magnetic structure is provided which includes a pair of end members disposed at the opposite ends of the abovementioned tube and a central leg member which extends axially inside of said tube. A magnetic armature or plunger is disposed to move reciprocally between an engaged position with respect to the central leg member of the associated stationary magnetic structure and another position which is spaced axially away from said central leg member. A substantially nonmagnetic tripping rod is provided to move with the associated armature axially through an opening in at least one of the end members of the stationary structure.

Description

United States Patent [72] Inventor Joseph D. Findley,Jr.

Pittsburgh, Pa.

[21] Appl. No. 22,915

[22] Filed Mar. 26, 1970 [45] Patented Dec. 21,1971

[73] Assignee Westinghouse Electric Corporation Pittsburgh, Pa;

[54] ELECTROMAGNETIC TRIP DEVICE FOR CIRCUIT m'rrznnur'rsns 8 Claims, 6 Drawing Figs.

52] u.s.c1 335/174, 335/255 51 lnt.Cl 1101119/ [501 FieldoiSearch 335/174, 175,172,25s,251,262,264

[5 6] References Cited UNlTED STATES PATENTS 1,593,384 7/1926 Brown 335/264 2,217,462 10/1940 Willmann 335/175 r 2,295,691 9/1942 Russell 335/ 2,651,744 9/1953 Acklin et a1. 335/251 3,426,304 2/1969 Cannon et al 335/255 Primary Examiner-Harold Broome Attorneys-A. T. Stratton and Clement L. Mcl-lale ABSTRACT: An electromagnetic trip device for a circuit interrupter or circuit breaker comprising an electrically conducting substantially nonmagnetic tube having a relatively large number of conductor turns of an energizing coil wound thereon. A stationary magnetic structure is provided which includes a pair of end members disposed at the opposite ends of g the above-mentioned tube and a central leg member which extends axially inside of said tube. A magnetic armature or plunger is disposed to move reciprocally between an engaged position with respect to the central leg member of the associated stationary magnetic structure and another position which is spaced axially away from said central leg member. A substantially nonmagnetic tripping rod is provided to move with the associated armature axially through an opening in at least one of the end members of the stationary structure.

PATENIED nEc21 ran 3629,74?

SHEET 1 [IF 2 SCI CLOSED TRIP FREE n4 INVENTOR g9 Joseph D. F|nd|ey,Jr.

ATTORNEY PATENTED 05021 I9?! 3629.747

SHEET 2 [IF 2 /L2 0 AV A CT?) C2 I L6 0 f 1 A f AVA O 0 PROTECTIVE Risa o RELAY OPERATING MECHANlSM ELECTROMAGNETIC TRIP DEVICE FOR CIRCUIT INTERRUPTERS BACKGROUND OFTHE INVENTION In certain types of circuit interrupters, such as network protectors, an electromagnetic trip coil is energized to actuate the tripping or opening of the circuit interrupter or circuit breaker. Where the energy required for the operation of the trip coil is derived from the electrical circuit which is protected by the circuit interrupter, the alternating current voltage applied to the trip coil may vary over a relatively wide range during abnormal operating conditions or fault conditions which occur in the protected circuit. For example, such a trip coil may be required to operate over a range of voltages which extends from 7 A to 106 percent ofa predetermined or normal full value. In certain applications, the speed of operation of such a trip coil may not be'critical even though it is essential that the trip coil operate properly or positively over the desired range of energizing voltages. If a particular trip coil of the type described is constructed to operate properly at the lower values of energizing voltage in the desired range, the impact or force produced by the operation of the trip coil may be such as to damage associated parts of the circuit interrupter when relatively higher voltages in the desired operating range are applied to the trip coil. It is therefore desirable to provide an improved trip coil of the type described for circuit interrupters which will operate over a relatively wide range of energizing voltages and which will not result in damaging impacts or forces applied to the associated parts of the associated circuit interrupter.

SUMMARY OF THE INVENTION In accordance with the invention, an electromagnetic trip device for a circuit interrupter is adapted to be energized by a source of alternating current voltage which varies over a predetermined range and comprises a generally tubular member formed from an electrically conducting, substantially nonmagnetic material, such as copper. An energizing coil comprising a relatively large number of conductor turns is wound on the tubular member and is electrically connected to the output terminals of a rectifier means, more specifically a full wave rectifier circuit, whose input terminals are adapted to be connected to a source of alternating current voltage which may vary over a predetermined range of values. The trip device also includes a stationary magnetic structure which comprises a pair of end members or plates disposed at the opposite ends of the tubular member and a central leg member which extends from one of the associated end members axially inside the associated tubular member. Where desired, a pair of electrically insulating washers may be secured to the opposite ends of the tubular member by suitable means to form a spool on which the turns of the energizing coil are wound with the washers being disposed between the turns of the energizing coil and the respective end members of the associated stationary magnetic structure. A generally cylindrical magnetic armature or plunger is disposed to extend axially at least partially inside the tubular member and to move reciprocally between an engaged position with respect to the central leg member of the stationary magnetic structure and another position which is spaced axially away from the central leg member. More specifically, the end of the armature which engages the central leg member may be generally truncated conical in configuration and the meeting end of the central leg member may include a recess of complementary shape which is adapted to receive the end of the armature which engages the central leg member. The latter end of the central leg member may have disposed therein an annular metallic member of substantially nonmagnetic material, such as brass, which is disposed to be engaged by the central portion of the associated armature in the engaged position of said armature to facilitate the release of the armature when the energizing coil is deenergized after being previously energized to attract the armature to engage the central leg member. A substantially nonmagnetic tripping rod is secured to the armature for movement therewith and extends axially through an opening in at least one of the end members of the stationary magnetic structure. In order to reset the armature when the energizing coil is deenergized, a biasing means such as a biasing spring, may be disposed on the tripping rod to bias the armature toward the position away from the associated central leg member.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be had to the preferred embodiment, exemplary of the invention, shown in the accompanying drawings in which:

FIG. I is a diagrammatic, partial view, in side elevation, ofa circuit interrupter or network protector embodying my invention showing the relative positions of certain parts of the operating mechanism of the circuit interrupter when the main separable contacts of the circuit interrupter are in'the closed position;

FIG. 2 is a view, similar to FIG. 1, illustrating the relative positions of certain parts of the operating mechanism of the circuit interrupter after the operating mechanism of the circuit interrupter has been tripped free by the operation of the trip coil which forms part of the circuit interrupter and after the main contacts of the circuit interrupter have been actuated to the open circuit position,

FIG. 3 is a view, similar to FIGS. 1 and 2, showing the relative positions of certain parts of the operating mechanism of the circuit interrupter when the main contacts are actuated to the open circuit position and the operating mechanism of the circuit interrupter has been automatically reset;

FIG. 4 is an enlarged view, partly in side elevation and partly in section, of the trip coil embodying the invention and certain associated parts of the operating mechanism of the circuit interrupter shown in FIGS. 1 through 3;

FIG. 5 is an enlarged fragmentary view of the trigger latch of the circuit interrupter in the trip-free position corresponding to the positions of the parts in FIG. 2; and

FIG. 6 is a diagrammatic view of the circuit connections associated with the circuit interrupter and the associated trip coil shown in FIGS. 1 through 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and FIG. 1 in particular, the circuit interrupter 10 shown therein comprises generally one or more sets of separable contact means Cl and SCI, an operating mechanism indicated generally at l00 and a trip device indicated generally at 50. More specifically, as shown in FIGS. I and 3, the movable contact structure Cl, may be rotatably supported by a relatively stationary supporting means, such as the fixed pivot pin 166, to move between an engaged or closed position with respect to the associated stationary contact means SCl, as shown in FIG. 1, and an open position with respect to said stationary contact means, as shown in FIG. 3.

The movable contact structure CI for each pole of the circuit interrupter 10 is pivotally connected by means of an operating rod or push rod 162 to one end of'an operating lever 152 which, in turn, is rotatably mounted on a main common operating shaft 154. One end of the operating rod 162 is pivotally connected to the movable contact structure C1 by the pivot pin 164 and the other end of the operating rod 162 is pivotally connected to one end of the operating lever 152 by the pivot pin 156 as shown in FIG. I. The main operating shaft 154 is rotatably supported by suitable relatively stationary supporting means (not shown) which form part of the circuit interrupter 10. As illustrated, the other end of the operating lever 152 is operatively connected to a suitable biasing means, such as the opening spring 182, which is normally held in tension when the circuit interrupter 10 is in the closed operating position shown in FIG. 1 to bias the operating lever. 152 in a generally counterclockwise direction about the main operating shaft 154. The operating mechanism 100 of the circuit interrupter may include a plurality of spaced operating levers similar to the operating lever 152 which correspond to the different pole units of the circuit interrupter 10 and which are mounted on the common operating shaft 154.

The operating mechanism 100 of the circuit interrupter 10 also includes a toggle linkage which assists in maintaining movable contact structure C1 in the closed position shown in FIG. 1 and which may also be employed in transmitting the closing forces to said movable contact structure during a closing operation of the circuit interrupter 10. More specifically, the toggle linkage includes a pair of

toggle links

142 and 144 which are pivotally connected together by a knee pivot pin 148 on which a roller 143 is rotatably supported. The other end of the toggle link 144 is pivotally connected to the operating lever 152 by the pivot pin 147, while the other end of the toggle link 142 is pivotally connected to the upper end of the trip-free lever 134 by the pivot pin 146, as shown in FIGS. 1 through 3. The trip-free lever 134 is rotatably supported by a fixed pivot pin 136. As illustrated, the trip'free lever 134 includes one or more rollers 132 which are rotatably mounted at the lower end of the lever 134 by suitable means such as associated pivot pins.

The

toggle linkage

142, 144 is releasably held in a slightly overcenter position as shown in FIG. 1 in order to maintain the circuit interrupter in the closed position by a latch lever 122 which is pivotally supported on the fixed shaft 124. As shown in FIG. 1, the left end of the latch lever 122 bears against the lower end of the trip-free lever 134 at the roller 132 to maintain the

toggle linkage

142, 144 in the slightly overcenter position shown in FIG. 1. The latch lever 122 is normally releasably held in a latching or holding position as shown in FIG. 1 by a trigger latch 114 which is actuable to an unlatching position by the operation of the trip device 50, as will be described hereinafter. A latch roller 112 is rotatably mounted on the right end of the latch lever 122 by a pivot pin 123 as shown in FIG. 4 and normally engages the lower end of the trigger latch 114. The trigger latch 114 is rotatably mounted or supported on a fixed pivot pin 116, as best shown in FIG. 4, which, in turn, is rotatably supported on a bracket member which is secured to one of the supporting plates 133 which form part of the supporting framework of the circuit interrupter 10. It is to be noted that the trigger latch 114 shown in FIG. 4 is biased in a counterclockwise direction with respect to the pivot pin 116 by a biasing torque spring 118 with one end of the spring 118 bearing against the trigger latch 114 and the other end bearing against the supporting framework of the circuit interrupter 10. As shown in FIGS. 1 and 4, the trigger latch 114 has mounted thereon an auxiliary plate 115 which moves with the trigger latch 114 and which is normally disposed in the path of movement of the tripping rod 99 which forms part of the trip device 50, as will be explained in detail hereinafter.

The electromagnetic trip device 50, as shown in FIG. 4, is supported on a supporting plate 135, which forms part of the framework of the circuit interrupter, by a supporting member 137 which is secured to the trip device 50 and which passes through the electrically insulating wall member 139. In general, the trip device 50 is disposed adjacent to the trigger latch 114 to actuate the release of the latch lever 122 to thereby actuate an opening or tripping operation of the circuit interrupter 10.

More specifically, the electromagnetic trip device 50, which is of the tractive type, as shown in FIG. 4, includes a central tubular member 52 which is formed from an electrically conducting, substantially nonmagnetic material, such as copper. Where desired, a pair of electrically insulating

washers

54, 56 may be disposed at the opposite ends of the tubular member 52 to extend outwardly or radially from said tubular member to form an overall spool. The insulating

washers

54 and 56 may be secured to the opposite ends of the tubular member 52 by suitable means, such as an epoxy cement or resin.

In order to produce the magnetic flux which is required during the operation of the trip device 50, an energizing or operating coil 62 is provided which includes a relatively large number of conductor turns which are wound on the tubular member 52 and which are disposed between the insulating

washers

54 and 56, where provided. In order to apply a unidirectional or direct current to the energizing coil 62 of the trip device 50 during the operation of the circuit interrupter 10 as shown diagrammatically in FIG. 6, the opposite ends of the energizing coil 62, as indicated by the

leads

62A and 62B, are electrically connected to the output terminals of a full wave bridge-type rectifier circuit 70 which includes a plurality of rectifier devices, such as silicon diodes. As shown in FIG. 4, the rectifier bridge circuit 70 may be supported or disposed adjacent to the trip device 50 and secured to the supporting plate by suitable means which pass through the electrically insulating member 139. The input terminals of the bridge rectifier circuit, 70 as shown in FIG. 6 are electrically connected to be energized from the electrical circuit protected by the circuit interrupter 10 when the movable contact 202 of the protective relay 200 closes between the line conductor indicated at L3 which is one of the alternating current line conductors in the electrical circuit protected by the circuit interrupter 10 and the ground connection, as indicated at G, which is electrically connected to the neutral conductor N shown in FIG. 6. The number of conductor turns included in the energizing coil 62 is relatively large in order to increase the effective inductance of the energizing coil and to retard the buildup of the current in said energizing coil and the corresponding magnetic flux when said energizing coil is energized during the operation of the trip device 50. For example, it has been found preferable to increase the number of conductor turns in a particular application to approximately between two and three times as many turns as would normally be required in an alternating current trip device of the same general type. The effective inductance of the energizing coil 62 is thereby increased in accordance with the square of the turns ratio between the different types of coils and is approximatelyv six times as great as an equivalent alternating current trip device of the same general type. Such a relatively large number of conductor turns and the corresponding inductance could normally not be employed in an alternating current trip coil of the same general type since the magnetic flux in a coil of the latter type must build up within one half cycle of the alternating current.

The electromagnetic trip device 50 also includes a stationary magnetic structure which comprises a pair of end members or plug

members

64 and 66 which are disposed at the opposite ends of the tubular member 52 and which are formed from a soft magnetic material, such as a suitable steel or iron. Each of the

magnetic end members

64 and 66 include central openings which are approximately the same size as the opening through the tubular member 52 and extend outwardly or radially from the tubular member 52 as illustrated to substantially the same distance as the conductor turns of the coil 62.

The stationary magnetic structure also includes a central leg member or bushing 94 which is disposed to extend axially inwardly inside the tubular member 52 for at least a portion of the distance between the opposite ends of said tubular member, as shown in FIG. 4. The central leg member 94 is also formed from a soft magnetic material, such as those previously mentioned and includes an externally threaded portion 94A which extends axially through the central opening in the end member 64 and through a substantially aligned opening provided in an additional end plate 44 which is provided to assist in retaining the different parts of the trip device in assembled relation, as will be explained hereinafter. The end plate 44 may also be formed from a soft magnetic material such as those previously mentioned. In order to retain the central leg member 94 in assembled relation with the end plate 44, suitable means, such as the nut 48, may be provided on the threaded portion of the central leg member 94 and tightened down to bear against the outside of the end plate 44 as shown in FIG. 4. It is to be noted that the central leg member 94 includes a central opening which extends axially therethrough to receive the tripping rod 99, as will be described more fully hereinafter. The inner end of the central leg member 94 also includes a recess which is generally truncated conical in configuration to receive the associated armature or plunger 92 during the operation of the trip device 50. In order to permit the release of the armature or plunger 92 from the engaged position, as will be explained hereinafter, a ring-shaped or annular member 84 is disposed in a central recess at the inner end of the central leg member 94 and is formed from a suitable substantially nonmagnetic, metallic material, such as brass. As just indicated, it is to be noted that the central leg member 94 acts as a guide bearing and support for the tripping rod 99 during the operation of the trip device 50.

As shown in FIG. 4, the armature or plunger 92 of the trip device 50 is generally cylindrical in configuration and is disposed to extend axially at least partially inside the tubular member 52. The armature 92 is also formed from a suitable soft magnetic material, such as those previously mentioned, and the inner end of the armature 92 is generally truncated conical in configuration which is complementary to the shape of the recess provided at the inner end of the central leg member 94 previously described. It is to be noted that the inner end of the armature 92 is normally spaced axially away from the inner end of the central leg member 94, as shown in FIG. 4 to provide a working nonmagnetic gap between the armature 92 and the central leg member 94 of the trip device 50. In addition, it is to be noted that when the coil 62 is deenergized and the armature 92 is in the normal position shown in FIG. 4, there is also provided a radial, nonmagnetic gap between the main body portion of the armature 92 and the magnetic end member 66 with at least a portion of the armature 92 being normally disposed in the central opening of the magnetic end member 66.

In order to provide a return path for the magnetic flux which results when the energizing coil 62 is energized during the operation of the trip device 50, an outer tubular member 68 is disposed to extend axially between the

magnetic end members

64 and 66 and to enclose the energizing coil 62 as shown in FIG. 4. The outer tubular member 68 is also formed from a suitable soft magnetic material, such as those previously mentioned. It is to be noted that each of the

magnetic end members

64 and 66 extend axially at least partially inside the associated outer tubular member 68 as shown in FIG. 4.

In order to actuate the trigger latch 114 when the energizing coil 62 is energized during the operation of the trip device 50, the trip device 50 also includes the tripping rod 99 which is secured to the armature 92 for movement therewith by suitable means such as one or more cross pins which pass through substantially aligned openings provided in the armature 92 and the tripping rod 99. The tripping rod 99 is formed from a substantially nonmagnetic material, such as a suitable type of stainless steel, and the left end of the tripping rod 99 passes axially through the central opening provided in the central leg member 94 beyond the end plate 44 to a point which is adjacent to but spaced from the trigger latch 114 as shown in FIG. 4. The right-hand portion of the tripping rod 99 passes through a central opening in an end plate 46 which acts as a guide bearing and support for the reciprocal movement of the armature or plunger 92 during the operation of the trip device 50. The end plate 46 is formed from a suitable nonmagnetic material, such as brass, in order to avoid any radial pull or force which might otherwise result if the movement of the armature or plunger 92 were not accurately centered within the central opening of the magnetic end member 66 and the tubular member 52.

In order to retain the various parts of the trip device 50 in assembledrelation as shown in FIG. 4, suitable means, such as a plurality of bolts 82, may be provided which extend axially between the

end plates

44 and 46 and which pass through substantially aligned openings provided in the

end plates

44 and 46.

In order to return the armature 92 to its normal operating position whenever the energizing coil 62 is deenergized, a suitable biasing means, such as a compression spring 97, may be disposed on the right-hand portion of the tripping rod 99 as viewed in FIG. 4. More specifically, a spring seat member 93 may be mounted on the tripping rod 99 at a location which is spaced axially away from the end plate 46 and the spring 97 may be disposed between the end plate 46 around the central opening through which the tripping rod 99 passes and which acts as a first spring seat and the spring seat member 93 which acts as a second spring seat as shown in FIG. 4.

In order to permit the manual actuation of the tripping rod 99 and the trigger latch 114 where desired, a metallic sleeve member 96 may be slidably mounted at the right end of the tripping rod 99 and retained thereon by suitable means, such as a washer and screw, which are disposed inside the sleeve member 96 to engage a shoulder inside said sleeve member. A

compression spring 91 is disposed on the tripping rod 99 between the spring seat member 93 previously mentioned and the sleeve member 96 to provide a certain amount of lost motion in the movement of the sleeve member 96 when said sleeve member is actuated by a manual actuating member (not shown).

As shown in FIG. 6, the circuit interrupter 10 may be of the three-phase type and include a plurality of movable contact structures C1, C2 and C3 which, when closed, electrically connect a first electrical circuit as indicated by the alternating current line conductors L4, L5 and L6 which may comprise a source of alternating current power and a second electrical circuit as indicated by the line conductors L1, L2 and L3, which may comprise a load circuit which is to be protected by the operation of the circuit interrupter 10. In addition, a neutral conductor as indicated at N may be provided and electrically connected to a ground connection as indicated at G. In a typical application, a plurality of current transformers CTl, CT2 and GT3 may be disposed in inductive relation with the line conductors L1, L2 and L3 and connected in circuit relation with a suitable protective relay 200 such as disclosed in greater detail in US. Pat. No. 2,817,059 which issued Dec. I7, 1957 to G. G. Grissinger et al. and which is assigned to the same assignee as the present application. When the protective relay 200 responds to an abnormal operating condition or fault condition in the electrical circuit protected by the circuit interrupter 10, the operation of the trip device 50 is actuated by the protective relay 200 through suitable means, such as the movable contact 202, which closes to thereby energize the operating or energizing coil 62 of the trip device 50 from the alternating current voltage between the line conductor L3 and the ground connection G which is applied at the input terminals of the bridge circuit 70. A unidirectional or direct current then flows from the output terminals of the rectifier bridge circuit through the conductor turns of the energizing coil 62.

In the operation of the trip device 50 when the energizing coil 62 is energized, as just described, by the operation of an associated means, such as the protective relay 200, the alternating current voltage applied at the input terminals of the rectifier bridge circuit 70 may vary over a relatively wide range depending upon the operating conditions in the electrical circuit which includes the line conductors L1, L2 and L3. As previously mentioned, the voltage applied at the input terminals of the rectifier bridge circuit may vary over a range such as 7 5% to 106 percent ofa normal full voltage depending upon the abnormal operating conditions in the above-mentioned electrical circuit. By rectifying the voltage that is applied to the energizing coil 62 of the trip device 50, the energizing coil 62 may include a relatively large number of conductor turns, as previously disclosed, which is important in slowing down or retarding the buildup of quirent in the energizing coil 62 and the corresponding buildup of magnetic flux in the trip device 50 which would otherwise result in undesirable forces or impacts exerted by the tripping rod 99 on the associated parts of the circuit interrupter 10 during the opera tion of the trip device 50. Such undesirable forces or impacts have been found to result in damage to the associated operating parts of the circuit interrupter 10 when the voltage applied to the energizing coil of an alternating current trip device of known construction is of a value which is toward the higher end of the desired operating range of voltages. It is to be noted that the number of conductor turns included in the operating coil of an alternating current-type trip device is inherently limited since the magnetic flux which is required for the operation of such a trip device must buildup within one half cycle of the alternating current voltage which is applied to the 7 operating coil of such a trip device.

' After the energizing coil 62 of the trip device is energized, the magnetic flux which is produced by the current flow through the conductor turns of the energizing coil 62starts to actuate the axial movement of the armature or plunger 92 from the normal position shown in FIG. 4 toward the left until the central portion of the inner end of the plunger 92 engages the inner end of the central leg member 94 which includes a recess which is adapted to receive the meeting end of the plunger 92. It is important to note that the electrically conducting tubular member 52 encloses the working nonmagnetic gap between the plunger 92 and the central leg member 94. As the working nonmagnetic or airgap decreases during the movement of the plunger 92, the magnetic flux tends to increase at a relatively fast rate but the eddy currents which are induced in the tubular member 52 during the movement of the plunger 92 produce an opposing magnetic flux which retards or delays the buildup of magnetic flux in the working nonmagnetic gap-between the plunger 92 and the central leg member 94 as the'plunger 92 moves toward the final engaged position to thereby reduce the impact that the tripping rod 99 exerts on the trigger latch 114 when the left end of the tripping rod 99 engages the trigger latch 114 and rotates it in a clockwise direction about the pivot pin 116 to thereby release the roller 112 and the associated latch lever 122.

Considering the overall operation of the circuit interrupter 10 during the operation of the trip device 50, it will be assumed initially that the movable contact structure Cl shown in FIG. 1 is in the closed position and that the energizing coil 62 of the trip device 50 is deenergized. When the trip device 50 is energized, the tripping rod 99 moves toward the left to rotate or 'actuate the trigger latch 114 through the auxiliary plate 115 to thereby release the roller 112 and the latch lever 122 shown in FIG. 1. The latch lever 122 will then be actuated in a counterclockwise direction about the fixed shaft 124 to the momentary position shown in FIG. 2 in which the rollers 132 at the lower end of the trip-free lever 134 rollup on the cam surface 122A of the lever 122, as shown in FIG. 2, to thereby release the left end of the toggle link 142 to move toward the left, as viewed in FIGS. 1 and 2 under the influence of the opening spring 182. During the movement of the

toggle linkage

142, 144 toward the left, the push rod 162 will be actuated to rotate the movable contact structure C1 to the open position shown in FIG. 2; After the trip-free lever 134 has rotated in a counterclockwise direction about the fixed pivot pin 136 to the position shown in FIG. 2, the knee pivot pin 148 of the

toggle linkage

142, 144 will slowly move to an undercenter position and the

toggle linkage

142, 144 will be actuated to a completely collapsed condition thereby permitting the other parts of the mechanism 100 to reset as shown in FIG.

After the movable contact structures of the circuit interrupter 10 are actuated to the open positions, as shown in FIG. 3 for the movable contact structure C1, the energizing coil 62 of the trip device 50 will then be deenergized and the armature or plunger 92 will then be actuated back from the engaged position to the normal operating position shown in FIG. 4 by the biasing spring 97. Various parts of the operating mechanism 100 will then be automatically reset in sequential fashion and the trigger latch 114 will be returned to its normal operating position as shown in FIG. 4 which is normally spaced from the left end of the tripping rod 99. The spacing between the rod 99 and the trigger latch 114 results in an impact force exerted on the trigger latch 114 by the tripping rod 99 during the operation of the trip device 50 which facilitates the overcoming of any frictional forces which may be present between the various parts of the operating mechanism 100. It is important to note that the release of the armature 92 from an engaged position with respect to the central leg member 94 of the stationary magnetic structure is facilitated by the substantially nonmagnetic annular member 84 which results in a slight nonmagnetic airgap between the leg member 94 and the armature 92 in the engaged position of said armature and which prevents the effects of residual magnetism in the stationary magnetic structure which might otherwise tend to retain the armature 92 in the engaged position against the influence of the force exerted on the armature 92 by the biasing spring 97.

In the overall operation of the circuit interrupter 10. after the movable contact structures, such as the movable contact structure C1, have been actuated to the open positions as shown in FIG. 3, the circuit interrupter 10 may be returned to the closed position shown in FIG. 1 by suitable means such as a closing cam (not shown) which may be disposed on the fixed shaft indicated in FIGS. 1 through 3 and which may be rotated by suitable means such as a closing spring or closing motor which rotates the cam to engage the roller 143 on the knee pivot of the

toggle linkage

142, 144 to actuate the

toggle linkage

142, 144 to the slightly overcenter position shown in FIG. 1 which actuates the movable contact structure C1 to the closed position shown in FIG. 1 through the operating lever 152 and the push rod 162.

It is to be understood that where desired the end plate 44 and the adjacent end member 64 may be combined and formed as a unitary end member from a suitable soft magnetic material, such as those previously mentioned. In addition, in certain applications, a one-piece, molded electrically insulating spool may be provided with the nonmagnetic, electrically conducting tubular member 52 disposed inside the central opening of the spool rather than forming the spool with a pair of separate washers cemented to the tubular member 52, as disclosed.

The apparatus embodying the teachings of this invention has several important advantages. For example, a trip device for a circuit interrupter as disclosed is uniquely adapted to operate over a wide range of input voltages without producing any undesirable impacts or forces which might otherwise damage the associated parts of the circuit interrupter and which still provides positive operation at voltages which are at the lower end of the desired operating range. These advantages result from the relatively large number of turns included in the energizing coil which retard or slow down the buildup of the magnetic flux when the energizing coil is initially energized and which are permitted by the rectifier bridge circuit which rectifies the alternating current applied at the input terminals of the bridge circuit before it is applied to the energizing coil 62. In addition, the buildup of magnetic flux or the increase of magnetic flux which results as the armature or plunger 92 moves toward the engaged position after the coil 62 is energized is retarded by the induced eddy currents which result in the electrically conductive tubular member 52 which surrounds the working nonmagnetic gap between the armature or plunger 92 and the associated central leg member 94. In addition, any tendency for the armature or plunger to remain in the engaged position due to the effects of residual magnetism in the stationary magnetic structure of the trip device 50 is avoided by the presence of the substantially nonmagnetic annular member 84 which is disposed in the recess at the end of the central leg member which is engaged by the armature or plunger 92 as previously explained.

I claim as my invention:

1. An electromagnetic trip device adapted to be connected to a source of alternating current voltage which varies over a predetermined range of voltage comprising a generally tubular member formed from an electrically conducting, substantially nonmagnetic material, an energizing coil comprising a relatively large number of conductor turns wound on said tubular member to retard the buildup of current in said coil and the corresponding magnetic flux when said coil is energized from said source, rectifier means having input terminals adapted to be connected to said source of alternating current and output terminals connected to said energizing coil, a stationary magnetic structure comprising a pair of end members disposed at the opposite ends of said tubular member and a central leg member extending from one of said end members axially inside said tubular member, a generally cylindrical magnetic armature disposed to extend axially at least partially inside said tubular member and to move reciprocally between an engaged position with respect to said central leg member and another position which is spaced axially away from said central leg member, the end of said armature which engages the central leg member of said stationary magnetic structure being generally truncated conical in shape, and the end of said central leg member which is engaged by said armature including a recess of complementary configuration which is adapted to receive said armature, a substantially nonmagnetic tripping rod secured to said armature for movement therewith and extending axially through an opening in one of said end members, said central leg member and the other of said end members including substantially aligned, axially extending central openings through which said tripping rod extends and projects outside of said tripping device, and means disposed on said rod for biasing said armature toward said another position.

2. The combination as claimed in claim 1 wherein said stationary magnetic structure includes an outer tubular member disposed around said energizing coil and extending axially between said pair of end members to provide a return path for the magnetic flux which results when said energizing coil is energized.

3. The combination as claimed in claim 1 wherein a central annular member formed from a metallic, substantially nonmagnetic material is disposed in said end of said central leg member which is engaged by said armature, said annular member being engaged by the central portion of said armature is in the engaged position with respect to said stationary magnetic structure.

4. The combination as claimed in claim 1 wherein said electromagnetic trip device is of the tractive type and an annular member is disposed in said end of the central leg member around said central opening to be engaged by the central portion of said armature when said armature is in the engaged position with respect to said stationary magnetic structure, said annular member being formed from a substantially nonmagnetic, metallic material.

5. The combination as claimed in claim 4 wherein a pair of electrically insulating washers are disposed at the opposite ends of said tubular member between said energizing coil and the respective end members of said stationary magnetic structure.

6. The combination as claimed in claim 4 wherein said annular member is formed from brass.

7. The combination as claimed in claim 2 wherein said electromagnetic trip device is of the tractive type and an annular member is disposed in said end of the central leg member around said central opening to be engaged by the central portion of said armature when said armature is in the engaged position with respect to said stationary magnetic structure, said annular member being formed from a substantially nonmagnetic, metallic material.

8. The combination as claimed in claim 5 wherein said electromagnetic trip device is of the tractive type and an annular member is disposed in said end of the central leg member around said central opening to be engaged by the central portion of said armature when said armature is in the engaged position with respect to said stationary magnetic structure, said annular member being formed from a substantially nonmagnetic, metallic material.