US3303441A

US3303441A - Circuit breaker with thermal trip means and means for shunting current around the thermal trip means

Info

Publication number: US3303441A
Application number: US410571A
Authority: US
Inventors: Charles R Paton; Yorgin Nick
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1964-11-12
Filing date: 1964-11-12
Publication date: 1967-02-07
Anticipated expiration: 1984-02-07
Also published as: BE693871A; GB1091519A

Description

"ONU

INVENTORS Charles R. Po'ron 8l Nick Yorgin FlG. 2

ATTORNEY Feb. 7, 1967 C R, PATON ET AL 3,303,441

CIRCUIT BREAKER WITH THERMAL TRIP MEANS AND MEANS FOR SHUNTING CURRENT AROUND THE THERMAL TRIP MEANS Filed NOV. 12, 1964 2 Sheets-Sheet 2 7 FIGS. E F'G-5- 34 fm 77"' 79 Q n l r 8| l l 35 3 |45 H9 FIG-'Z United States Patent O CIRCUIT EREAKER WITH THERMAL TRIP MEANS AND MEANS FR SI-IUNTING C U R R E N 'I' AROUND THE THERMAL TRIP MEANS Charles R. Paton, Daugherty Township, New Brighton, and Nick Yorgin, Economy Township, Ambridge, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation ot' Pennsylvania Filed Nov. 12, 1964, Ser. No. 410,571 6 Ciaims. (Cl. 335-12) This invention relates generally to circuit breakers and more particularly to circuit breakers for controlling lighting and moderate power circuits.

At many circuit breaker installations it is desirable to provide a circuit breaker embodying a current-carrying thermally responsive trip element for effecting a timedelayed tripping operation upon the occurrence of an overload current below a predetermined value and an electromagnetic trip structure for eifecting an instantaneous tripping operation upon the occurrence of an overload above the predetermined value. In order to limit the current through the current-carrying thermally responsive trip device to thereby prevent damage to this trip device, it is desirable to shunt current past the thermally responsive trip device upon the occurrence of an electromagnetic tripping operation.

Accordingly, an object of this invention is to provide a circuit breaker embodying a current-carrying thermally responsive trip device and an electromagnetic trip structure, with means for limiting the current in the thermally responsive trip device under certain .abnormal conditions.

Another object of this invention is to provide an improved circuit breaker embodying a thermally responsive current carrying bimetal trip device and an electroresponsive magnet-and-armature trip structure with means shunting current through the magnet-and-armature structure upon the occurrence of an electroresponsive tripping operation.

Another object of this invention is to provide an improved circuit breaker With thermal and magnetic tripping means.

The invention, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description when read in conjunction with the accompanying drawings.

In said drawings:

FIGURE l is a top plan view, on a reduced scale of a circuit breaker embodying the principal features of this invention;

FIG. 2 is a sectional view taken generally along the line II-II of FIG. 1;

FIG. 3 is a side View, on an enlarged scale relative to FIG. 2, of parts of the tripping device seen in FIG. 2; the tripping device being viewed in FIG. 3 from the side opposite the side of the viewer in FIG. 2;

FIG. 4 is a vie-w similar to FIG. 3 with the parts being shown in a tripping position reached during an electromagnetic tripping operation;

FIG. 5 is a sectional view taken generally valong the line V-V of FIG. 4;

FIG. 6 is a view of the supporting plates and tripping bar structure seen in broken lines in FIG. 1;

FIG. 7 is a side view of the structure seen in FIG. 6 prior to the time when the structure is mounted in the circuit breaker; and

FIGS. 8 and 9 are side and end views respectively of a supporting plate seen in FIGS. 3 and 4.

Referring to FIGS. 1 and 2 of the drawings, the circuit breaker 5 shown therein is a three-pole molded- ICC case type circuit breaker. An insulating base 11 and an insulating cover 13 are secured together to form the housing of the circuit breaker. The housing 11, 13 cornprises cooperating insulating barriers 14 that serve to insulate adjacent pole units of the circuit breaker from each other. A stationary contact 15, a movable contact 17 and an are extinguishing unit 18 are provided for each pole unit of the breaker. The breaker also comprises an operating mechanism 19 and a latching device 2t) disposed in the center pole unit. A thermal and electromagnetic tripping device 21 is provided in each of the pole units for effecting automatic opening of the circuit breaker. The operating mechanism and latching device are similar to the operating mechanism and latching device disclosed in the patents to E. I. Walker et al., Patent No. 3,103,565, issued September 10, 1963.

The stationary contact 15 for each pole unit is tixedly mounted on the inner end of a conducting strip 23. In each pole unit, a well known type of solderless terminal connector 25 is connected to the outer end of each of the conducting strips 23. The movable contact 17 for each of the pole units is mounted on a contact arm structure 27 that is secured to an insulating tie bar 31. The tie bar 31 is common to all three of the pole units and it is rotatably mounted at the opposite ends thereof in suitable supports in the opposite side walls of the circuit breaker.

The operating mechanism 19 is disposed in the center pole unit and supported therein by means of two supporting

plates

34 and 35. The plates 34 and 35 (FIGS. 6 and 7) are provided with lower portions 36 that pass through suitable openings in the base 11 of the insulating housing and are riveted over at 37 (FIG. 2) to thereby support the

plates

34 and 35 in position in the center pole unit. The operating mechanism 19 (FIG. 2) comprises an inverted U-shaped operating lever 41 having its inner ends pivoted in notches 43 (FIG. 7) in the supporting

plates

34 and 35. An operating lever 46, including an arcuate shield 47, is mounted on the outer end of the operating lever 41. A handle portion 49 of the operating member 46 extends out through an opening 51 in the cover 13. The contact arm 27 for the center pole unit is operatively connected by means of a toggle, comprising toggle links 53 and 55, to a releasable member or cradle 57 that is pivotally mounted on a pin 59 that is supported in the

side plates

34, 35. The toggle links 53 and 55 are pivotally connected together by a knee pivot pin 61. The toggle link 53 is pivotally connected to the releasable member 57 by means of a pivot pin 63, and the toggle link 55 is pivotally connected to the contact arm structure 27 by means of a pivot pin 65. Overcenter springs 67 are connected under tension between the knee pivot pin 61 of the toggle 53, 55, and an upper spring support 68 that is secured to the yoke portion of the operating lever 41.

The contacts are manually opened by movement of the handle 49 in a counterclockwise (FIG. 2) direction from the on to the oit position. This movement changes the line of action of the Overcenter springs 67 to cause collapse of the toggle 53, 55 and counterclockwise movement of the contact arm 27 of the center pole unit to the open position, which movement rotates the tie bar 31 to simultaneously move all three of the contact yarms 27 to the Iopen position. The contacts are manually closed by reverse movement of the operating handle 49 from the olif to the on position. This movement changes the line of action of the Overcenter springs 67 to straighten the toggle 53, 55 to thereby move the Contact arm 27 of the center pole unit to the closed position, which movement rotates the tie bar 31 to simultaneously move all three of the contact arms 27 to the closed position.

The latching mechanism 20 comprises a main latch member 71 that is supported on a pin 73 and is rotatably mounted on the supporting'plates 34, 35. The latch mem-V ber 71 is biased by means of a tension spring in a clockwise (FIG. 2)l or unlatching direction. The main latch 71 engages the free end of the releasable member 57 to restrain the releasable member 57 in the latched position. The main latch 71 is releasably held in the latched position by engagement of a portion 75 thereof with the periphery of a trip bar 77 that has a generally cylindrical shaped outer surface except at a part thereof wherein there is a notch 79 (FIGS. 2 and 6), which notch is disposed lat the part of the trip bar that is adjacent to the part 75 of the main latch 71. The trip bar 77 extends through openings in the plates 34, 35 (FIGS. 6 and 7) and also through suitable openings in the insulating barriers 14 that separate adjacent pole units of the circuit breaker. A trip member S1 is'iixedly attached to the trip bar 77 in the center pole unit. Two trip members 83 (FIGS. l, 6 and 7) are mounted on the ends of the trip bar 77 in the two outer pole units of the circuit breaker.

There is a separate thermal and electromagnetic tripping device 21 in each of the three pole units of the circuit breaker. Only the center pole unit tripping device 21 (FIG. 2) will be specifically described. A support member 85 (FIGS. 8 and 9) is provided with two bentover lower leg parts 87 yand a lower part 89. During assembly of the breaker, the lower part 89 is positioned to extend through an opening in the insulating housing base 11 and the main part 85 is positioned against one of the side walls or barriers of the associated pole unit. The lower part 89 is then drawn down and riveted over at 99 (FIG. 2) during which operation the pressure of the bent-over leg parts 87 (FIGS. 8 and 9) against the inside lower surface of the base 11 forces the main part of the member 85 against the associated side wall or barrier to thereby support the member in the breaker. An armature support 91 (FIG. 3) is pivotally supported intermediate the ends thereof at 93 on the support plate 85. A torsion spring 95 biases the armature support 91 in a counterclorckwise (FIGS. 3 and 4) direction about the pivot 93, which movement is limited by engagement of the member 91 with a stop 97 that is xedly supported on the support 35. An armature 99 is ixedly secured to the lower end of the arm-ature support 91. The opposite or upper end 1191 of the armature support 91 Vis disposed adjacent the trip member 81. A ilexible conductor 163 is secured at one end thereof to the armature 99 and at the other end thereof t-o a conducting support 105. A screw 107 passes through an opening in a conductor 109, an opening in the conductor S and an opening in the lower leg portion of a conducting bimetal 111 to electrically connect the

members

109, 105, 111 and to xedly secure these members to the housing base 11. The vertical part of the bimetal 111 passes between the legs of a generally U-shaped magnet yoke member 115 that is xedly secured to a rigid conducting terminal member 117. The member 117 is provided with a lower generally horizontal part 119. As can be seen in FIG. 2, la well known type of solderless terminal connector 121 is secured to the outer end 119 of the conduct-or 117. A conducting tab 123 (FIGS. 3 and 4) is xedly secured to the uppe-r end of the bimetal 111. A flexible conductor 125 is secured at one end to the tab 123 and at the other end to the conductor 117 to electrically connect the tab 123 and conductor 117. The bimetal 111 and tab 123 are provided with a tapped opening, and an adjusting screw 127 is threaded into the tapped opening. The screw 127 can be rotated to vary the relative position of the end of the screw with respect to the trip member 81 to thereby adjust the thermal tripping operation of the circuit breaker. The supporting plate 85 is provided with an upper bent-over part 128 (FIGS. 3, 8 and 9) that engages the trip member 81. The part 128 can be bent more or less than the amount shown in FIGS. 3, 8 and 9 to move the 4 trip member 81 to thereby vary the position of the

parts

77, 81, 83. This operation will adjust the amount of tripping bar rotation that is necessary to effect la tripping operation.

The circuit through each pole unit of the circuit breaker extends from the terminal connector 25 (FIG. 2) through the conductor 23, the contacts 15, 17, the contact arm 27, a flexible conductor 131 that is attached at one end to the contact arm 27 and at the other end to the conductor 109, i the conductor 199, the conductor 165,the bimetal 111,k

the tab 123, the flexible conductor 125, the terminal conductor 117, to the terminal connector 121 (FIG. 2). As can be seen in FIG. 2, the flexible conductor 131 is disposed at one end thereof in a conducting eyelet 133 and these parts are welded or lbrazed to the associated contact arm structure 27. The eyelet is tianged to support the exible conductor 131 beyond the brazed area during operation of the contact arm to thereby minimize fraying action at the brazed area.

Because the parts are viewed in FIGS. 3 and 4 from the side opposite from the side from which these parts are viewed in FIG. 2, it can be understood that the direction of movement of the parts in FIGS. 3 and 4 will be reversed when the description is applied to FIG. 2.

Referring to FIGS. l, 3 and 6, it will be noted that the trip ybar '77 is provided with the trip member 83 in the two outer pole units and the trip member 81 in the center pole unit. The thermal and electromagnetic trip device 21 is the same in each pole unit except that the adjusting screw 127 (FIG. 3) and the upper part 161 of the armature support 91 in the two -outer pole units are disposed adjacent the trip members 83 (FIGS. 1 land 2) rather than being disposed adjacent the center-pole trip member 81 as is disclosed in FIGS. 2, 3 and 4. The

trip members

83 and 81 function in the same manner to rotate the

common structure

83, 77, S1 during a tripping operation.

Referring to FIG. 3, when an overload current below a predetermined value passes through any of the pole units, the bimetal 111 in that pole unit is heated and it deflects to the left (FIG. 3) whereupon the screw 127 engages the trip member 81 (or one of the trip members S3 if the overload is in one of the outerV pole units) to rotate the common tripping bar 77 in a counterclockwise (FIG. 3) direct-ion. This counterclockwise (FIG. 3) movement of the trip member 811 as seen in FIG. 3 is really a clockwise rotation of this member as seen in FIG. 2. As the trip `bar members 77 (FIG. 2) rotates in a clockwise direction, the notch 79 moves adjacent the part 75 of the trip member 71 whereupon the springs 67 operating through the releasable member 57 and the latch 71, serve to move the member 71 in a clockwise (FIG. 2) direction, snapping the part of the member 71 into the notch 79 this movement releases the trip member 57. When released, the trip member 57 rotates clockwise about the pivot 59 (FIG. 2) under the iniiuence of the overcenter tension springs 67 causing collapse of the toggle 53, 55 .and opening movement of the contact arms 27, through counterclockwise rotation of the common trip bar 31, for all of the pole units. During this Vmovement, the -handle 49 is moved in a manner well known in the art to a tripped position intermediate the off and on positions thereby giving a visual indication that a tripping operation has occurred.

Before the contacts can be closed following an automatic opening or tripping operation, it is necessary to reset and relatch the mechanism. This is accomplished by moving the handle 49 counterclockwise from the intermediate or tripped position to the extreme off position. During this movement, a projection 137 on the operating lever 41 engages a shoulder 139 on the releasable trip member 57 moving the trip member 57 counterclockwise about the pivot 59. Near the end of this movement, the latching end of the tr-ip member 57 engages the latch member 71 moving the latch member 71 against the bias of a torsion spring that is mounted on `the pin 73, t-o the latching position. As soon as the projection 75 on the trip member 71 clears the corner of the notch 79 in the trip bar 77, a torsion spring rotates the tripping bar 77 to the latching position seen in FIG. 2 wherein the part 75 of the latch member 71 again engages the periphery of the trip bar 77 to again latch the parts in the position seen in FIGS. 2 and 3. Thereafter, the circuit breaker can be operated in the same manner as Was hereinbefore described.

The hereinbef-ore described thermal tripping operation occurs upon the occurrence of lesser overloads and with a time delay. Thus, if the lesser overload is only a momentary overload the circuit breaker will not trip open. Nuisance tripping operations are, therefore, avoided. Upon the occurrence of an overload above the predetermined value, it is desi-rable to tr-ip the circuit breaker instantaneously. Thus, for example, when a short circuit occurs, the circuit -breaker will be tripped instantaneously by operation of an electromagnet trip means comprising the

members

111, 99, 115. Upon the occurence of an overload current above the predetermined value, the current flowing thr-ough the bimetal 111 generates sufficient magnetic ux to prov-ide suicient magnetic attraction between the magnet member `115 and armature 99 to move the armature support 91 in a counterclockwise (FIG. 3) direction about the pivot 93 moving the armature 99 toward the member 115. During this movement, the upper part 101 of the armature support 91 engages the trip member 81 (or one of the trip members 83 if the overload occurs in one of the outer pole units) to rotate the trip bar 77 in a tripping direction to elfe-ct a tripping operation in the same manner hereinbefore described.

As was previously described, the normal circuit through the circuit breaker extends (FIG. 3) from the conductor 109, through the conductor 105, the bimetal 111, the conducting tab 123, the flexible conductor 125, to the generally rigid supporting conductor 117. If a severe overload or short circuit were to pass through the bimetal 111, it is possible that the current carrying bimetal 111 would become heated to such an extent that it would take a permanent set in a distorted position. The thermal tripping function of the circuit breaker would then be out of calibration and the thermal tripping operation would not be dependable for adequate protection of the controlled circuit. Thus, it is desirable to shunt current past the bimetal 111 when the overload is severe. Improved means is provided for shunting current past the bimetal 111 during electromagnetic tripping operations.

The armature 99 and yoke 115 are formed from a conducting metal -having high magnetic permeability such as steel. A contact 141 (FIGS. 3-5) is welded or otherwise xedly secured to the armature 99 at one side of the armature, and a contact 143 .is welded or otherwise xedly secured to be a bent-over part 145 (FIG. 5) of one leg of the generally U-shaped magnet member opposite the contact 141. As was previously described, the ilexible conductor 103 is secured to the conductor 105 and armature 99 on one side of the bimetal 111, and the magnet member 115 engages and is supported on the conductor 117 on the opposite side of the bimetal 111. When the armature 99 and yoke 115 are separated as is seen in FIG. 3, the circuit passes through the bimetal 111. Upon the occurrence of an electromagnetic tripping operation, the

contacts

141, 143 engage (FIGS. 4 and 5) thereby providing a shunt path from the conductor 109 (FIG. 4) through the flexible conductor 103, the conducting armature 99, the

contacts

141, 143, the bent-over part 145 of the conducting yoke 115, the yoke 115, to the terminal conductor 117. Thus, upon the occurence of an electromagnetic tripping operation current is shunted around the bimetal 111 thereby protecting the bimetal 111 from an excessive `amount of current to thereby provide that the bimetal will not become unduly heated. The

steel members

99 and 115 have large cross-sectional areas to minimize the resistance of the shunt path. The shunt path can have a resistance of, for example, approximately one-fifth that of the bimetal to thereby carry most of the current around the bimetal when the shunt path is closed.

As is seen in FIG. 5, the ends of the U-shaped magnet member 115 are coated at 151 with a suitable insulation. If the

steel members

99 and 115 were to engage and carry high current through the engaging surfaces, these members might weld together at the engaging surfaces. The insulation 151 is provided to prevent the welding of the

members

99 and 115 if these members should engage at surfaces other than the contact surfaces during an electromagnetic tripping operation.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and arrangement of parts thereof may be made without departing from some of the essential features of the invention.

What is claimed is:

1. A circuit breaker comprising relatively movable contacts and opening means operable to effect opening of said contacts, a movable member operatively movable to effect operation of said -opening means, current-carrying thermally responsive trip means operable upon the occurrence of an overload current below a predetermined value to operatively move said movable member, electromagnetic trip means comprising a yoke and armature and operable upon the occurrence of an overload current vabove said predetermined value to operatively move said movable member, a conducting shunt path shunting current around said thermally responsive trip means upon operation of said electromagnetic trip means, said shunt path comprising cooperable contact means on said yoke and armature closing upon operation of said electromagnetic trip means to close said shunt path.

2. A circuit breaker comprising relatively movable contacts and opening means operable to effect opening of said contacts, a movable member operatively movable to effect operation of said opening means, a thermal 4trip comprising a current-carrying bimetal connected in the circuit of said breaker and flexing upon the occurrence an overload current labove said predetermined value said operatively move said movable member, an electromagnetic trip comprising a rst magnet member and a second magnet member, a support conductor, said first magnet member comprising a generally U-shaped member supported on said support conductor with the opposite legs thereof extending on opposite sides of said bimetal spaced from said bimetal, upon the occurrence of an overload current above said predetermined value said iirst magnet member being energized by the current flow through said bimetal to magnetically attract said second magnet member to move said second magnet member toward said first magnet member to a closed position to thereby operatively move said movable member, a contact surface on said rst magnet member, said second magnet member having a contact thereon, and when said second magnet member is moved to said closed position said contact engaging said contact surface to close a conducting shunt path around said bimetal from said contact to said support conductor through said contact surface and said first magnet member.

3. A cir-cuit breaker comprising relatively movable contacts and opening means operable to elect opening of said contacts, a movable member operatively movable to effect operation of said opening means, a thermal trip comprising a current-carrying bimetal connected in the circuit of said circuit breaker and flexing upon the occurrence of overload currents below a predetermined value to operatively move said movable member, an electromagnetic trip comprising a yoke and armature supported to be magnetically energized by the current through said circuit breaker, said yoke and armature comprising conducting members, upon the occurrence of overloads above said predetermined value said armature being magnetically attracted to said yoke to move said movable member to effect an electromagnetic tripping operation, upon the occurrence of said electromagnetic tripping operation said armature moving to close a conducting shunt path through said armature and said yoke and around said bimetal to reduce the current fiow through said bimetal.

4. A circuit breaker comprising relatively movable contacts and opening means operable to effect opening of said contacts, a movable member operatively movable to effect operation of said opening means, a currentcarrying bimetal member connected in the circuit of said breaker and fiexing upon the occurrence of an overload current below a predetermined value to operatively move said movable member, an electromagnetic trip comprising a generally U-shaped magnet yoke supported such that said bimetal member passes between the legs thereof, said electromagnetic trip comprising a magnet armature supported for movement toward and away from said yoke, a first shunt path contact supported on said armature and a second shunt path contact supported on said yoke, said armature and said yoke comprising conducting members, conducting means comprising a shunt path around said bimetal through said armature said shunt path contacts and said yoke when said armature is moved to a cl-osed position, and upon the occurrence of an overload current above said predetermined value when said armature is in the open position the current through said bimetal generating sufficient magnetic flux in said yoke and armature to cause said armature to be magnetically attracted toward said yoke to the closed position to close said shunt path and to operatively move said movable member.

5. A circuit breaker comprising relatively movable contacts and opening means -operable to effect opening of said contacts, a movable member operatively movable to effect operation of said opening means, a first conducting member, a bimetal, a second conducting member, means connecting said first conducting membersaid bimetal-said second conducting member and said contacts in electrical series, an electromagnetic trip comprising a yoke and an armature, said yoke comprising a generally U-shaped member connected to said first conducting member with the opposite legs thereof extending on opposite sides of said bimetal spaced from said bimetal, a contact surface on said yoke, a contact surface on said armature, a shunt conducting means effecting an electrical connection of said contact surfaceA on said armature with said second conducting member, upon the occurrence of an overload current below a predetermined value through said bimetal said bimetal exing independent of said yoke to operatively move said movable member to effect a thermal tripping operation, upon the occurrence of an overload current above said predetermined value said yoke being magnetically energized by the current flow through said bimetal to magnetically attract said armature whereupon said armature moves toward said yoke to operatively move said movable member to effect an electromagnetic tripping operation, and upon the occurrence of said electromagnetic tripping operation said contact surface on said armature engaging said contact surface on said yoke to close a shunt path through said first conducting member-said yoke-said contact surface on said yokesaid contact surface on said armature-said shunt conducting means-to said second conducting member which shunt path bypasses said bimetal.

6. A circuit breaker comprising relatively movable contacts and opening means operable to effect opening of said contacts, a movable member operatively movable to effect operation of said opening means, a first conducting member, a bimetal, a first flexible conductor electrically connecting said first conducting member with said bimetal, a second conducting member, said first conducting member-said first flexible conductorsaid bimetal-said second conducting member and said contacts being connected in electrical series in the circuit of said circuit breaker, an electromagnetic trip comprising a yoke and an armature, said yoke comprising a generally U-shaped member supported on said first conducting member with the opposite legs thereof extending on opposite sides of said bimetal spaced from said bimetal, a contact surface on one of the legs of said yoke, a contact surface on said armature, a flexible shunt conductor electrically connecting said armature with said second conducting member, upon the occurrence of an overload current below a predetermined value through said bimetal said bimetal flexing independent of said yoke to operatively move said movable member to effect a thermal tripping operation, upon the occurrence of an overload current above said predetermined value the current in said bimetal generating sufficient magnetic fiux in said yoke and armature to effect attraction of said armature toward said yoke whereupon said armature moves toward said yoke to a closed position to operatively move said movable member to effect an electromagnetic tripping operation, and when said armature moves to said closed position said contact surface on said armature engaging said contact surface on said yoke to close an electrical shunt path through said first conducting member-said yoke-said contact surface on said yoke-said contact surface on said armaturesaid armature-said flexible shunt conductor-to said second conducting member which shunt path bypasses said bimetal.

References Cited by the Examiner UNITED STATES PATENTS 2,419,125 4/ 1947 Dorfman et al. 200-88 X 2,989,605 6/1961 Leonard 200-88 2,989,606 6/1961 Walker et al. 20G-88 3,005,066 10/ 1961 Powell 200-88 X BERNARD A. GILHEANY, Primary Examiner.

R, N. ENVALL, Assistant Examiner.

Claims

1. A CIRCUIT BREAKER COMPRISING RELATIVELY MOVABLE CONTACTS AND OPENING MEANS OPERABLE TO EFFECT OPENING OF SAID CONTACTS, A MOVABLE MEMBER OPERATIVELY MOVABLE TO EFFECT OPERATION OF SAID OPENING MEANS, CURRENT-CARRYING THERMALLY RESPONSIVE TRIP MEANS OPERABLE UPON THE OCCURRENCE OF AN OVERLOAD CURRENT BELOW A PREDETERMINED VALUE TO OPERATIVELY MOVE SAID MOVABLE MEMBER, ELECTROMAGNETIC TRIP MEANS COMPRISING A YOKE AND ARMATURE AND OPERABLE UPON THE OCCURRENCE OF AN OVERLOAD CURRENT ABOVE SAID PREDETERMINED VALUE TO OPERATIVELY MOVE SAID MOVABLE MEMBER, A CONDUCTING SHUNT PATH SHUNTING CURRENT AROUND SAID THERMALLY RESPONSIVE TRIP MEANS UPON OPERATION OF SAID ELECTROMAGNETIC TRIP MEANS, SAID SHUNT PATH COMPRISING COOPERABLE CONTACT MEANS ON SAID YOKE AND ARMATURE CLOSING UPON OPERATION OF SAID ELECTROMAGNETIC TRIP MEANS TO CLOSE SAID SHUNT PATH.