US3246098A - Molded-case electric circuit breaker - Google Patents

Molded-case electric circuit breaker Download PDF

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Publication number
US3246098A
US3246098A US382732A US38273264A US3246098A US 3246098 A US3246098 A US 3246098A US 382732 A US382732 A US 382732A US 38273264 A US38273264 A US 38273264A US 3246098 A US3246098 A US 3246098A
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United States
Prior art keywords
magnetic core
circuit breaker
armature
case
armature support
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US382732A
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English (en)
Inventor
John S Hall
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Schneider Electric USA Inc
Original Assignee
Square D Co
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Filing date
Publication date
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Publication of US3246098A publication Critical patent/US3246098A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H71/00—Details of the protective switches or relays covered by groups H01H73/00 - H01H83/00
    • H01H71/10—Operating or release mechanisms
    • H01H71/12—Automatic release mechanisms with or without manual release
    • H01H71/40—Combined electrothermal and electromagnetic mechanisms

Definitions

  • the trip device also includes a magnetic assembly that becomes operative upon the occurrence of a severe overload or a fault condition in the circuit to release the operating mechanism more quickly than can the thermally responsive element.
  • Such former circuit breakers have been designed to operate satisfactorily in branch circuits rated at fifteen amperes, 120 volts, but these former circuit breakers will not operate satisfactorily to protect branch circuits rated at five amperes, 240 volts.
  • the principal object of the present invention is to provide a trip device of increased sensitivity that is rendered operative upon flow of a relatively low overload or fault current to open the contacts of a circuit breaker.
  • Circuit breakers are mounted in panelboards which have become standardized in design, and thus the exterior dimensions or configuration of circuit breakers must be such that they can be accepted in the panelboard. Therefore, it is important that any improvement or change in the trip device of a circuit breaker be accomplished without necessitating a change in a critical external dimension or configuration of the circuit breaker.
  • a trip device operable at lower currents preferably has the same general configuration as the trip device it is to replace and the size is restricted. Further, operation at higher voltages increases the difficulty of extinguishing arcs that occur upon contact separation.
  • a rearrangement of circuitry through the circuit breaker Patented Apr. 12, 1966 is necessary to provide space for a larger arcing chamber and de-ionizing plates.
  • Another object of the present invention is to provide a trip device of increased sensitivity and a larger arcing chamber for a circuit breaker of lower current and higher voltage rating without requiring a change in a critical dimension of the circuit breaker, thereby enabling the circuit breaker to be used in the same size electrical panelboard as circuit breakers of lower voltage and higher current rating.
  • One method of increasing the sensitivity of the fault current response of a trip device comprising a magnetic core and an associated armature, and wherein a magnetic flux is induced in the magnetic core by an electrical conductor, is to increase the effective ampere turns with respect to the core. Since the amount of current is determined by the circuit in which the circuit breaker is used, the effective ampere turns can be increased only by increasing the number of turns of the electrical conductor about the core. Because the exterior dimensions of the trip device cannot be materially increased, the increased number of turns must be accommodated substantially within the confines of the original trip device.
  • Another object of the present invention is to provide a trip device in which a thermally responsive conductor and a non-thermally responsive conductor are electrically connected in series and are supported in cooperative relation with a magnetic core and with each other to provide a plurality of turns about the core without increasing a critical dimension of the circuit breaker, thereby enabling the circuit breaker to be used in the same size electrical panelboard as circuit breakers of lower voltage and higher current rating.
  • Another object is to provide an improved trip device comprising a magnetic yoke through which a thermally responsive element in the form of a bimetallic strip extends and wherein the operative fiux in the yoke is developed in part by current flowing through the thermally responsive element and in part by current flowing through a conductor wound about one leg of the yoke and electrically in series with the thermally responsive element.
  • a further object is to provide an improved trip device comprising a thermally responsive bimetal that responds to heat developed by relatively small currents.
  • Yet another object is to provide an improved magnetic core and armature support which is deformable in accordance with the size of air gap required to provide a circuit breaker having a desired magnetic trip point.
  • FIG. 1 is a view of a circuit breaker constructed in accordance with this invention, the cover having been removed, certain parts being shown in section, and the mechanism being shown in on position;
  • FIG. 2 is a sectional view taken generally along the line 2-2 of FIG. 1 but including the cover;
  • FIG. 3 is a fragmentary sectional view taken generally along the line 3-3 of FIG. 4 but including the cover;
  • FIG. 4 is a fragmentary view similar to FIG. 1 but showing the mechanism of the circuit breaker in tripped' position;
  • FIG. 5 is a view similar to FIG. 4 but showing the mechanism of the circuit breaker in off position
  • FIG. 6 is a fragmentary view of the combination magnetic core and armature support and certain associated parts of the circuit breaker of FIG. 1 as viewed from the left in FIG. 1;
  • FIG. 7 is a fragmentary view similar to the righthand portion of FIG. 1 but showing a second embodiment of the invention.
  • FIG. 8 is a sectional view taken genenally along the line 88 of FIG. 7 but including the cover;
  • FIG. 9 is a view of the line terminal and certain associated parts of the circuit breaker of FIG. 7 as viewed from the left in FIG. 7;
  • FIG. 10 is a view similar to FIG. 7 but with certain portions broken away;
  • PEG. 11 is a view similar to FIG. 10 but illustrating an adjusted air gap between the armature and core of the circuit breaker.
  • FIG. 12 is a perspective view of the combination magnetic core and armature support of the circuit breaker.
  • FIGS. l6 show an embodiment of the invention for low current ratings.
  • the molded case of the circuit breaker of FIGS. 1-6 includes a base 26* and a cover 21 molded of insulating material and secured together by a plurality of rivets 22.
  • the base and cover are provided with molded recesses and barriers for supporting the other parts of the circuit breaker, as will be understood.
  • a load terminal including a shiftable connector body 24 and a clamping screw 25' is provided adjacent one end of the case.
  • the clamping screw bears against one side of an end portion of a terminal strap 2 3 to move thi connector body and clamp a wire (not shown) between the connector body and the other side of the terminal strap.
  • a stationary contact 23 is secured to the other end portion of the terminal strap 26 for cooperation with a movable contact 3%) secured to the bight portion of a generally U-shaped contact arm 32 pivotally supported in a pair of inwardly extending spaced leg portions 33 of an operating handle 34 pivotally supported in the base 2%? and cover 21.
  • a hole 35 is provided in the handle 34 for the reception of a handle tie bar (not shown) when it is desired to provide a multiple circuit breaker similar to that shown in British Patent No. 827,740, published February 10, 1960.
  • a slid able arc shield member 36 formed of insulating material is hooked to the contact arm 32.
  • An overcenter tension spring 38 is hooked at one end to the bight portion of the contact arm 32 and at the other end to a generally U-shaped releasably latehable cradle member or trip lever 4t? pivotally mounted adjacent one end on a projection 41 of the base 20 between the load terminal 24 and the contact arm 32 and releasably latehable at the other end in a slot 43 of an armature member 44 provided with a reversely bent tail portion 45.
  • the trip lever 49 extend through the handle 34 between the spaced leg portions 33 and carries a reset pin 46 cooperable with the leg portions 33 in the resetting or relatching of the trip lever after it has tripped.
  • a hole 48 is provided in the trip lever for the reception of a pin (not shown) cooperable with a common-trip crossbar (not shown) mountable in the base 2t and cover 21 when knockouts such as the knockout 5d shown in the base 2% are removed to provide a mul'tipole circuit breaker similar to that shown in the aforesaid Patent No. 827,740.
  • the armature dd is provided with a thin generally Z- shaped latch plate 52 extending through the slot 43 and having opposite end portions secured to opposite sides of the armature on opposite sides of the slot.
  • the latch plate 52 is shown as being thicker than it is in actual practice due to limitations of drawing.
  • a combination magnetic core and armature support which includes a relatively large generally U-shaped magnetic core portion 54, a smaller generally U-shaped armature support portion 55, and a connecting portion 56 extending along the inner surface of the base 2% and connecting one leg portion of the m agetic core portion 54 with a corresponding leg portion of the armature support portion 55.
  • a cylindrical projection 58 on the base 20 extends through an opening in the connecting portion 56 and the adjoining leg of the armature support portion 55, and a tongue 59 extend ing oppositely of the connecting portion 56 from the adjoining leg of the magnetic core portion 54- is anchored or received in a recess in a boss 60 on the base 2i?
  • the armature 44 is pivotally supported on the armature support portion 55 and is biased clockwise as viewed in FIGS. 1, 4, and 5 by a helical compression spring 62 seated in a wall portion of the base 29.
  • a line terminal 64 is provided adjacent the other end of the case from the load terminal 24.
  • the line terminal 64- is generally Ushaped as shown in FIG. 6 to provide a pair of plug-in type terminal jaws.
  • a solid wire conductor 66 is secured at one end to the line terminal 64 and is wound several times around the leg portion of the magnetic core portion 54 opposite the connecting portion 56 and around an insulating sleeve s7 thereon and is secured at the other end to one end of a mounting bracket 68 held in position against a pair of rounded raised bearing portions 71 and 73 on an end wall portion of the base 26 by a screw 69.
  • a bimetallic member is secured at one end to the other end of the bracket es and extends through the magnetic core portion 5 between the legs thereof.
  • the bracket 68 is resilently deformable by rotation of the screw 6? to vary the position of the free end of the bimetallic member 7% with respect to the tail portion 45 of the armature 44- and thus calibrate the thermal tripping point of the circuit breaker.
  • a flexible braided wire conductor or cable 72 is secured at one end to the other or free end of the bimetallic member 76 and is secured at the other end to the contact arm 32.
  • An are chute assembly including a plurality of deionizing plates 7 held in spaced relationship to each other in a form-ed insulating fiberboard enclosure '75 is provided for the separable contacts .13 and 30.
  • the base 20 is provided with a pair of vent passages 76 and 77 extending from opposite sides of the arc chute assembly, the passage '77 venting between the jaws of the line terminal 64.
  • a mechanical mounting clip 78 is provided adjacent the other end of the case from the line terminal 64.
  • Movement of the handle 34 from the position shown in FIG. 1 to the position shown in FIG. 5 shifts the pivot point of the contact arm 32 across the axis of the spring 33 and causes the spring to pivot the contact arm to the off position, and conversely, movement of the handle back to the position of FIG. 1 causes the spring to pivot the contact arm back to the on position.
  • the unlatching of the trip lever as from the latch plate 52 in the slot 43 of t 1% armature 34 may be caused either thermally by engagement of the free end of the bimetallic member '70 with the tail of the armature upon sustained moderate overload current or magnetically by sufficient energization of the magnetic core portion 54 upon a heavy overload such as that caused by a short circuit current.
  • the thermal and magnetic tripping unit herein discosed lends itself very readily to production of circuit breakers of various current ratings.
  • a relatively large number of turns may be provided in the winding of the conductor 66 about the magnetic core portion 54 to produce sufiicient magnetic flux to trip the circuit breaker upon occurrence of relatively low short circuit currents, and the conductor 66 may be made of nickel-chromium or other high resistance wire to produce additional heat for activating the bimetallic member 70 upon relatively low sustained overload currents.
  • fewer turns may be provided in the conductor 66, and the material thereof may be changed to copper to reduce the heat input to the bimetallic member 70.
  • the construction shown in the modification of FIGS. 711 may be used.
  • the conduct-or 66 has been replaced by a formed conductive strap member 80 secured at one end to the line terminal 64 and extending outside of the magnetic core portion 54 to the mounting bracket 68 to which its other end is secured.
  • the strap member 80, bracket 68, and bimetallic member 70 thus provide merely one turn for the magnetic circuit defined by the magnetic core portion 54 and the armature 44. The number of turns cannot be further reduced without eliminating the magnetic flux, but circuit breakers with still higher current ratings may be produced by increasing the air gap as best shown in FIGS. 10 and 11.
  • connection between the tongue 59 and its associated leg of the magnetic core portion 54 is weakened by the forming of a recess in one side of the tongue, leaving a relatively narrow connecting portion 82 joining the rest of the tongue to the magnetic core portion.
  • the connecting portion 82 may be laterally bent in one direction be fore assembly of a circuit breaker to increase the air gap in the assembly and thus produce a circuit breaker with a higher magnetic trip point, or the connecting portion may be bent in an opposite direction to decrease the air gap.
  • the armature 44 is shown in the relative position it assumes when latched, and an angle A is shown between the armature and the magnetic core portion 54.
  • FIG. 11 the angle A has been increased by bending of the connecting portion 82 before assembly of the circuit breaker, thus increasing the air gap and producing a circuit breaker having a higher magnetic trip point.
  • circuit breaker of this invention and that of the aforesaid patent can be used with the same size panelboard, yet the circuit breaker of this invention has been provided with a larger arc chute so as to be able to handle higher voltages and with a tripping device capable of operating both thermally and magnetically at lower currents than the corresponding currents of the prior device of the aforesaid patent.
  • An electric circuit breaker comprising a molded case, a pair of separable contacts in said case, a releasably latchable trip lever pivotally mounted in said case and releasable from a latched position to effect separation of said contacts, an integral magnetic core and armature support member disposed in said case and including a generally U-shaped magnetic core portion and a generally U-shaped armature support portion, and an armature pivotally mounted on said armature support portion and having a free end portion normally spaced from and adapted to be attracted toward said magnetic core portion to effect release of said trip lever, the length of the leg portions of said magnetic core portion measured from the bight portion thereof being at least as great as the length of said bight portion measured between said leg portions and the greater portion of the length of one leg portion of said magnetic core portion being free of direct connection to the corresponding one leg portion of said armature support portion.
  • An electric circuit breaker as claimed in claim 1 including a line terminal electrically connected to a movable one of said contacts both in an open and in a closed position thereof with respect to a stationary one of said contacts by means including a formed electrically conductive strap member disposed outside said magnetic core portion between said magnetic core portion and a wall of said case.
  • An electric circuit breaker as claimed in claim 1 including a line terminal electrically connected to a movable one of said contacts both in an open and in a closed position thereof with respect to a stationary one of said contacts by means including an electrical conductor wound around said one leg portion of said magnetic core portion.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Breakers (AREA)
  • Electromagnets (AREA)
US382732A 1964-03-13 1964-07-15 Molded-case electric circuit breaker Expired - Lifetime US3246098A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB10610/64A GB1031971A (en) 1964-03-13 1964-03-13 Improvements in or relating to electric circuit breakers

Publications (1)

Publication Number Publication Date
US3246098A true US3246098A (en) 1966-04-12

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US382732A Expired - Lifetime US3246098A (en) 1964-03-13 1964-07-15 Molded-case electric circuit breaker

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US (1) US3246098A (de)
DE (1) DE1513442B2 (de)
FR (1) FR1427417A (de)
GB (1) GB1031971A (de)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3467920A (en) * 1966-11-05 1969-09-16 Square D Co Molded case circuit breaker with sensitive thermal and magnetic trip mechanism
US3470507A (en) * 1966-11-05 1969-09-30 Square D Co Earth-leakage sensing circuit breaker
US4232282A (en) * 1978-12-18 1980-11-04 Gould Inc. Circuit breaker having means to facilitate assembly thereof
EP0035693A1 (de) * 1980-03-06 1981-09-16 BROWN, BOVERI & CIE Aktiengesellschaft Mannheim Schaltwerk für elektrische Installationsschaltgeräte
US4481491A (en) * 1983-01-06 1984-11-06 General Electric Company Insulated latch-cradle mechanism
DE3339401A1 (de) * 1983-10-29 1985-05-09 Sursum Elektrizitätsgesellschaft Leyhausen GmbH & Co, 8500 Nürnberg Selbstschalter zum aufsetzen auf schienen
EP0143022A1 (de) * 1983-10-21 1985-05-29 Merlin Gerin Thermischer und magnetischer Auslöser für Selbstschalter
US4609895A (en) * 1983-10-29 1986-09-02 Sursum Elektrizitatsgesellschaft Leyhausen Gmbh & Co. Automatic switch with integral contact indicator
US4614928A (en) * 1983-10-29 1986-09-30 Sursum Elektrizitatsgesellschaft Leyhausen Gmbh & Co. Automatic switch with an arc blast field
WO1992002065A1 (en) * 1990-07-19 1992-02-06 Square D Company Plug-in circuit breaker
US5130685A (en) * 1991-01-28 1992-07-14 General Electric Company Molded case circuit breaker operating cradle configuration
US5294901A (en) * 1992-09-24 1994-03-15 General Electric Company Molded case circuit breaker insulated armature latch arrangement
US20040036562A1 (en) * 2002-08-21 2004-02-26 Siebels Randall L. Latch for an electrical device
EP2966667A1 (de) * 2014-07-09 2016-01-13 Siemens Industry, Inc. Schutzschalter mit niedrigem absoluten wert, schutzschalter, auslösungsmechanismen und auslösungsverfahren

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2897314A (en) * 1956-06-11 1959-07-28 Fed Pacific Electric Co Circuit breakers with thermal and magnetic tripping
US2902560A (en) * 1955-05-18 1959-09-01 Square D Co Circuit breaker
US3098136A (en) * 1955-06-09 1963-07-16 Square D Co Circuit breaker
US3178535A (en) * 1957-04-12 1965-04-13 Westinghouse Electric Corp Automatic circuit breaker with improved bimetallic and electromagnetic trip device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2902560A (en) * 1955-05-18 1959-09-01 Square D Co Circuit breaker
US3098136A (en) * 1955-06-09 1963-07-16 Square D Co Circuit breaker
US2897314A (en) * 1956-06-11 1959-07-28 Fed Pacific Electric Co Circuit breakers with thermal and magnetic tripping
US3178535A (en) * 1957-04-12 1965-04-13 Westinghouse Electric Corp Automatic circuit breaker with improved bimetallic and electromagnetic trip device

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3470507A (en) * 1966-11-05 1969-09-30 Square D Co Earth-leakage sensing circuit breaker
US3467920A (en) * 1966-11-05 1969-09-16 Square D Co Molded case circuit breaker with sensitive thermal and magnetic trip mechanism
US4232282A (en) * 1978-12-18 1980-11-04 Gould Inc. Circuit breaker having means to facilitate assembly thereof
EP0035693A1 (de) * 1980-03-06 1981-09-16 BROWN, BOVERI & CIE Aktiengesellschaft Mannheim Schaltwerk für elektrische Installationsschaltgeräte
US4481491A (en) * 1983-01-06 1984-11-06 General Electric Company Insulated latch-cradle mechanism
EP0143022A1 (de) * 1983-10-21 1985-05-29 Merlin Gerin Thermischer und magnetischer Auslöser für Selbstschalter
AU570739B2 (en) * 1983-10-29 1988-03-24 ABL Sursum Bayerische Elektrazubehor G.m.b.H. & Co.Kg Automatic switch with arc blast field
US4614928A (en) * 1983-10-29 1986-09-30 Sursum Elektrizitatsgesellschaft Leyhausen Gmbh & Co. Automatic switch with an arc blast field
US4617540A (en) * 1983-10-29 1986-10-14 Sursum Elektrizitatsgesellschaft Leyhausen Gmbh & Co. Automatic switch, rail-mounted
DE3339401A1 (de) * 1983-10-29 1985-05-09 Sursum Elektrizitätsgesellschaft Leyhausen GmbH & Co, 8500 Nürnberg Selbstschalter zum aufsetzen auf schienen
AU573635B2 (en) * 1983-10-29 1988-06-16 Square D Company Automatic switch for rail mounting
US4609895A (en) * 1983-10-29 1986-09-02 Sursum Elektrizitatsgesellschaft Leyhausen Gmbh & Co. Automatic switch with integral contact indicator
US5179491A (en) * 1990-07-19 1993-01-12 Square D Company Plug-in circuit breaker
WO1992002065A1 (en) * 1990-07-19 1992-02-06 Square D Company Plug-in circuit breaker
US5130685A (en) * 1991-01-28 1992-07-14 General Electric Company Molded case circuit breaker operating cradle configuration
US5294901A (en) * 1992-09-24 1994-03-15 General Electric Company Molded case circuit breaker insulated armature latch arrangement
US20040036562A1 (en) * 2002-08-21 2004-02-26 Siebels Randall L. Latch for an electrical device
US6801111B2 (en) * 2002-08-21 2004-10-05 Square D Company Latch for an electrical device
EP2966667A1 (de) * 2014-07-09 2016-01-13 Siemens Industry, Inc. Schutzschalter mit niedrigem absoluten wert, schutzschalter, auslösungsmechanismen und auslösungsverfahren
US9595413B2 (en) 2014-07-09 2017-03-14 Siemens Industry, Inc. Low instantaneous level circuit breakers, circuit breaker tripping mechanisms, and tripping methods

Also Published As

Publication number Publication date
DE1513442A1 (de) 1969-07-03
DE1513442B2 (de) 1971-12-09
FR1427417A (fr) 1966-02-04
GB1031971A (en) 1966-06-02

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