CA1087231A - Electromagnetic contactor comprising magnetic arc blowout means - Google Patents

Abstract

A B S T R A C T
ELECTROMAGNETIC CONTACTOR
A magnetic contractor including arc blowout means comprising a continuous-duty coil which is constantly connected in circuit with the current path through the contractor and provides sufficient magnetizing force to effect arc transfer from, the separating contacts to the arc chute of the contactor, and an intermittent-duty coil which is effectively connected in circuit so as to boost said magnetizing force only in response to such arc trans-fer. The continuous-duty coil preferably is a single-turn coil requiring relatively little space yet formed rela-tively heavy conductor material having a high continuous current-carrying capability.

Description

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This application is a Divisional Application of copending Canadian patent application No. 270,856 filed February l, 1977.
The invention relates to an electromagnetic contactor.
In many industries, such as marine, railroad, mining, offshore drilling, offroad construction and the like, contactors are used where space is at a premium.
Thus, some of the machines employed in these fields of application are specifically designed to use contactors having a particular size, and any new contactor to be substituted for an original one must have essentially the '1 same dimensions even though its continuous current-carrying capability and current-interruption rating may be desired to be higher. It is for this reason that the outer dimensions of contactors are a primary consideration in determining the acceptance of contactors by industry and, hence, their commercial success.
It is the principal object of the invention to provide an improved arc blowout and interrupting arrange-ment permitting the continuous current-carrying capability and interrupting capacity of a contactor of a given size to be increased or, conversely, the size of a contactor having a given rating to be reduced.
Accordingly, there is disclosed herein an elec-~ tromagnetic contactor comprising means forming a current ;j path through the contactor and including separable con-tacts, an arc chute disposed adjacent said contacts for receiving and e~tinguishing electric arcs drawn between ~t .. d~

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the contacts upon separation thereof, and arc blowout means for providing a magnetic field subjecting each arc, when drawn, to a force directed inwards of the arc chute, said arc blowout means comprising a ferromagnetic core, and a pair of coils both disposed to magnetize said core when energized, one of said coils being a continuous-duty coil which is constantly connected in circuit with said current path and, upon current flow therethrough, provides sufficient Magnetizing force to effect transfer of each arc from the separating contacts to the arc chute, and the other coil being an intermittent-duty coil which is effec-tively connected in series with the continuous-duty coil only in response to the transfer of an arc from the sepa-rating contacts to the arc chute.
The above arrangement combining a continuous-duty coil and an intermittent-duty coil offers several advantages, chief among them the requirement for the continuous-duty coil under all load conditions to generate only enough magnetizing force to effect a transfer of the arc from the separating contacts to the arc chute, where-upon the intermittent-duty coil becomes effective to boost the magnetizing force and thereby provide optimum blowout field conditions for arc interruption. This means, of course, that the continuous-duty coil can be, and prefer-ably is, a single-turn coil which not only requires rela-tively little space but also lends itself to being formed from fairly heavy conductor material having a high contin-uous current-carrying capability. The intermittent-duty coil, on the other hand, is required to carry current only for the short duration of arc interruption following each contact separation, and therefore can be a multiple-turn coil formed of considerably lighter conductor material which adds relatively little to the overall space require-- ments of the blowout means.
A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a left side view of a contactor : .

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Fig. 2 is a front view of the contactor with the arc chute removed;
Fig. 3 is a sectional view of the contactor of Fig. l;
Fig. 4 is a fragmentary plan view of the sta-tionary contact; and Fig. 5 is a horizontal view taken on the line V-V of Fig. 1.
Referring to Fig. l, the contactor shown therein and generally designated with numeral 1 is of the general type described in U.S. patent specification No. 3,511,350.
It comprises a base plate 3, electromagnetic means in the form of an electromagnet S, an electrically insulating housing 7, an arc blowout unit 9, arc chute 11, a sta-tionary contact assembly comprising a conductive contact supporting bracket 25 together with a stationary contact structure 13 mounted thereon, and a movable contact assem-bly including a conductive contact supporting bracket 19, having thereon a movable contact 15.
A current path extends through the contactor 1 from a line terminal 21 through the blowout unit 9, the contact supporting bracket 25, the contacts 13, 15, the contact supporting bracket 19, a contact shunt connector 25 29, shunts 31, and a shunt connector 33 to a load terminal 35.
The stationary contact structure 13 comprises several, such as two, fixed contact sections 37, 38 (Fig.
4), and a pivotal contact section 41 between the fixed sections. The fixed contact sections 37, 38 are secured by similar bolts 43 to the contact supporting bracket 25 which in turn is secured by spaced bolts 45 to an end portion 23 of a blowout coil 133. Thus, there is optimal electrical contact between the fixed contact sections 37, 38 and the bracket 25, and optimal electrical contact at 17 between the bracket 25 and the end portion 23 of the coil 133. Moreover, the bracket 25 and the contact sec-tions 37, 38, 41 form a stationary contact subassembly ,~

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which is replaceable without removing the line connection to the line terminal 21.
As shown more particularly in Fig. 3, the piv-otal contact section 41 is pivotally mounted on the brack-et 25 which may be an extruded member having a reversed-J
configuration, and which includes an upturned portion 47 defining a pivot or knife edge 49. The pivotal contact section 41 has formed therein a groove 51 having a V-shaped cross-section, in which the pivot edge 49 is seat-ed. A coil spring 53 is disposed between the bracket 25and the pivotal contact section 41 to maintain the latter seated upon the pivot edge 49 and, at the same time, to bias it for pivotal movement thereon towards the movable contact 15 (i.e. clockwise, as viewed in Figs. 1 and 3).
A stop pin 59 on the pivotal contact section 41 cooperates with stop surfaces on the fixed contact sections 37 and 38 to limit the movement of the pivotal contact section 41 under the action of the spring 53 to a position in which the contact surface 55 of the pivotal contact section is projected out of a plane (indicated in Fig. 4 by line 57) containing the contact surfaces of the fixed contact sections 37 and 38, as seen from Fig. 4. The pivot edge 49 corresponding to the pivot axis of the contact section 41 is substantially aligned with said plane 57, whereby contact wipe and resulting contact wear are minimized.
When the movable contact 15 moves from the closed to the open position (Fig. 3), an arc 39 occurs only between the moving contact 15 and the contact surface 55 of the pivotal contact section 41, since separation of the movable contact 15 from the pivotal contact section 41 occurs after separation from the fixed contact sections 37, 38, so that the latter remain relatively clean and cool during operation. Small sheets 63 of insulating material are disposed between the fixed contact sections 35 37, 39 and the pivotal section 41 to space the contact sections apart and to prevent them from becoming welded together due to arcing. The sheets 63 also serve to retain the compression spring 53 in its proper position.

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In order to reduce the electric resistance and, hence, heating at the pivotal connection between the pivotal section 41 and conductive support bracket 25, the pivot edge 49 and the groove 51 are provided silver surfaces formed, for example5 by brazing in place inlays of silver.
The advantages of providing the spring-loaded pivotal contact section 41 between the two fixed contact sections 37, 39 reside in a better continuous current-carrying capacity, in restricting arcing to the pivotal contact section since it closes before and opens after the fixed contact sections, and in a better vibration resist-ance.
The movable-contact supporting bracket 19 has limited freedom to move torsionally, that is, to twist, so as to enable the contact 15 to properly engage both fixed contact sections 37, 38. The movable contact supporting bracket 19 and the shunt connector 29 are connected by bolts 67 to the free end of a lever 65 which forms part of the movable contact assembly and is generally T-shaped, the shunt connector 29 having the shunts 31 connected thereto by means of bolts 68 (Fig. 3). At its lower end, the lever 65 is pivotally supported on a mounting bracket 69, its vertical and horizontal movements being limited by a roll pin 71 extending from an upturned portion of the bracket 69 and thro-ugh an aperture 73 which is formed in the lever 65 and is larger in diameter than the pin 71. A
lower end po:rtion of the lever 65 extends into a slot 75 in the bracket 69 to prevent disengagement of the lever 65 from the pin 71.
A washer 77 disposed on the pin 71 between the upturned portion of the bracket 69 and the lever 65 pro-vides for free tortional movement of the lever.
The lever 65 is additionally guided by coupling means operatively connecting the lever 65 to an armature 89 of the electromagnet 5 at a location distant from the pivot axes of the lever 65 and the armature 89, the pivot axis of the latter at 109 being proximate and parallel to the first axis of the lever. The coupling means comprise ., ~ ~ , ~ 372~

a U-shaped bracke~ 79, a coil spring 81, and a link 83.
The bracket 79 straddles the lever 65 and is provided with out-turned flanges 85 by means of which it is secured to the armature 89 by bolts 87 (Fig. 2) extending through openings 86 in the flanges 85. The openings 86 are elong-ated in order to permit lateral adjustment of the bracket 79 and, hence, proper alignment of the movable contact 15 with the stationary contact structure 13. The link 83 which extends through the bracket 79, carries adjacent its outer (righthand, as viewed in Figs. 1 and 3) end a pin 93 wnich coacts with the outer surface of the bight portion of the U-shaped bracket 79 to form a pivot connection between the link 83 and the armature 89 (to which the bracket is secured, thus in effect forming part of it), and carries, adjacent its inner (lefthand) end, a pin 95 coacting with the lever 65, at the side thereof facing the structure 89, so as to form a pivot connection between the link 83 and the lever 65. The latter has formed therein a notch 97 for receiving the pin 95. The coil spring 81, being disposed about the link 83, is compressed between the bight of the bracket 79 and a washer 99 (Fig. 1) seated against the lever 65, thereby spring-loading the lever and the link 83 in a contact closed direction. The coupling means just described permit linear displacement to occur, at the coupling means, between the armature 89 and the lever 65 during pivotal movements thereof, and the pivotal supports of, and pivotal connections between, the armature ancl the lever result in very low friction. In order to further reduce friction, the pins 93 and 95 preferably are of the roller type.
From the foregoing, it will be appreciated that upon actuation of the armature 89 from its dropout posi-tion, shown in Fig. 3, to its sealed or actuated position, shown in Fig. 1, the movable contact 15, which is a one-piece member spanning all three of the stationary contactsections 37, 38, 41, will first engage the pivotal contact section 41, rocking it counterclockwise, and will then engage the fixed contact sections 37, 38, whereupon move-- ~ :, : , .

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` ~87233 men~ of the movable contact assembly 15, 19, 29, 65 is arrested. However, the movement of the armature 89 toward its sealed position continues as overtravel and causes the spring 81 to be compressed, thereby increasing the spring force applied through the springseat washer 99 to the lever 65 and thence applied as contact pressure to the contacts 13, 15. This increased contact pressure, togeth-er with the freedom of limited torsional movement permit-ted by the loose fit of the lever 65 in the slot 75 and on the roll pin 71 as well as the flexibility of the shunts 31 which are made of fine braided wire, will assure that a firm and full engagement between the contact surfaces of the movable and stationary contacts is maintained despite variations in component parts due to manufacturing toler-ances and/or normal wear. To allow for such variations, it is also desirable to provide for an overtravel gap at one or each end of the link 83 when the contacts 13, 15 are new.
The operating electromagnet 5 (Fig. 1) consists 20 of the armature 89, a U-shaped magnetic frame 101, a round magnetic core 103, an operating coil 105, and a magnetic pole face 107. The armature 89 has a beveled lower end forming a knife-edge bearing surface 109 which rests upon the base plate 3 and upon which the armature is pivotable.
The armature 89 is held against lateral displacement thereof by upturned ears 90 of the base plate 3 and is held against upward movement thereof away from the plate 3 by pins 91 (Fig. 3) extending below the ears 90 from opposite sides of the armature.
The mounting bracket 69 is bolted to the base plate 3 and has an upper flange portion which serves as a spring seat for a kick-out spring 111 which acts upon an arm 113 bolted, at 115, to the armature 89 so that, when the electromagnet 5 is de-energized, the spring 111 moves the armature 89 and, consequently, the movable contact assembly clockwise to open the contacts 13, 15. The free end of the arm 113 may be used to operate electrical interlocks (not shown) associated with the contactor 1, or .
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to provide mechanical interlocking between the arc chute 11 and the contacts 13, 15.
A leaf spring 112 (Fig. 1) fastened at 114 (Fig.
1) to the bracket 69 is provided to make contact with a flange 116 on an e~tension 118 of a load-side arc horn 151 and thereby complete an electrical path therefrom to the base plate 3. When the arc chute 11 is removed for any purpose, such as maintenance, while the electromagnet 5 is de-energized and the arm 113 consequently is in its broken-line position indicated at 113b, the spring leaf 112 moves to the broken-line position 112a thereof shown in Fig. 1 in which its lower end is in the path of upward movement of an ear 113a on the arm 113, thereby preventing the armature from being actuated to its sealed or contact closed position until the arc chute is replaced.
In some circumstances it is desired to provide an overcurrent latch adapted to prevent the contacts 13, from opening upon the occurrence of a load current exceeding a predetermined value, even if the electromag-netic is de-energized, and su~sequently, when the load current has decreased to a second predetermined value, to allow the contacts 13, 15 to open if the electromagnet 5 is still de-energized. Th-us, a typical contactor used in industry may from time .o time see load currents from 4 to 10 times the rating of the contactor. If this overload condition persists, an overload relay will normally act to de-energize the operating coil of the contactor which then will ordinarily interrupt the flow of load current.
However, in some special applications it is not necessary 3 for the contactor to be opened under overload conditions, and for this purpose the contactor illustrated herein is provided with a latch mechanism comprising a latch lever 117 (Fig. 1), a latch magnet 119, and a latch roller 121 provided at least on one side of the armature 89, depend-ing upon whether one or two latch levers, such as lever ' 117, are utilized. The latch lever 117 is pivotally supported on the housing 7 at 123, and includes an up-turned hook portion 125 engaging the latch roller 121 when .

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the armature 89 is in its actuated position and the latch magnet 119 is energized. Upon de-energization of the latch magnet 119, a coil spring 127 moves the lever 117 to the broken-line position 117a shown in Fig. 1, thereby to disengage the hook 125 from the roller 121. The lever 117 includes a downward extension 129 connected at its lower end to an armature 131. The latch magnet 119 (Fig. 5) comprises a U-shaped magnetic yoke disposed around the load terminal 35. Under normal operating conditions, a large air gap 132 (Fig. 1) exists between the armature 131 and the pole face of the latch magnet 119, and the hook 125 is disengaged from the roller 121. When a load cur-rent flows through the shunt connector 33 and the load terminal 35, as indicated in Fig. 5 by arrows 131b, it magnetizes the latch magnet 119 and the armature 131, as indicated by arrows 131c. When the load current and, consequently, the magnetizing force reach a level at which the resultant force of attraction acting upon the armature 131 exceeds the unlatching force of the coil spring 127, the latch armature 131 is attracted to the latch magnet 119 so that the latch lever 117 is moved to its latching position in which the hook 125 is engaged with the latch roller 121.
Referring now in particular to Figs. 1 to 3, the arc blowout unit 9 of the contactor 1 comprises a ferro-magnetic core 135 and the magnetic blowout coil 133 looped thereabout. The coil 133, being supported on the insulat-ing base 7, consists of a single turn formed by a looped portion of a conductor, one end portion of which consti-tutes the line terminal 21, and an opposite end portion ofwhich has connected thereto the stationary contact assem-bly 13, 25. In addition to the coil 133 which is contin-uously in circuit with the current path through the con-tactor, the blowout unit 9 includes an auxiliary coil 137 which operates intermittently in that it becomes effect-ive, upon opening of the contacts 13, 15, only when the ' arc 39 drawn therebetween is transferred to a line-side arc horn 141.

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The auxiliary coil 137 has one end portion 137a thereof connected by suitable means, such as a screw 139, to the blowout coil 133 adjacent the end thereof which is connected to stationary contact supporting bracket 25, and has an opposite end portion 137b thereof connected to an extension 141 of a line side arc horn assembly 140 through a conductor 143 extending through an insulator mount 145.
The auxiliary coil 137 has several, such as four, turns around the core 135. A pair of pole pieces 147, 149 (see also Fig. 2) of ferromagnetic material extend from the opposite ends of the core 135 to opposite sides of the arc chute 11. Thus, when load current flows, a magnetic field is generated between the pole pieces which will assist in transferring an arc from the separating contacts 13, 15 onto the arc horns 141 and 151.
From the foregoing description it follows that the single-turn coil 133, which consists of relatively heavy conductor material and therefore is capable of continuously carrying relatively heavy currents, is con-stantly part of the current path through the contactor 1and, thus, is a continuous-duty coil. The multiple-turn auxiliary coil 137, on the other hand, is connected into circuit only when the contacts 13, 15 are opened and the resultant arc 39 is transferred onto the arc horns 141, 151, thus being an intermittent-duty coil. Under heavy load conditions, the single-turn continuous-duty coil 133 will provide enough magnetizing force to saturate the core 135 and to assure that maximum blowout field strength is available and optimum blowout field conditions for arc interruption exist as the contacts 13, 15 are opened;
under such heavy load conditions, then, the auxiliary coil 137 would not be needed. However, at light loads, the single-turn coil 133 alone is unable to develop enough magnetizing force, and under such conditions a blowout field strength adequate for effective arc interruption is obtained due to the extra magnetizing force provided by the multiple-turn auxiliary coil 137.

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Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electromagnetic contactor comprising means forming a current path through the contactor and including separable contacts, an arc chute disposed adja-cent said contacts for receiving and extinguishing elec-tric arcs drawn between the contacts upon separation thereof, and arc blowout means for providing a magnetic field subjecting each arc, when drawn, to a force directed inwards of the arc chute, said arc blowout means compris-ing a ferromagnetic core, and a pair of coils both dis-posed to magnetize said core when energized, one of said coils being a continuous-duty coil which is constantly connected in circuit with said current path and, upon current flow therethrough, provides sufficient magnetizing force to effect transfer of each arc from the separating contacts to the arc chute, and the other coil being an intermittent-duty coil which is effectively connected in series with the continuous-duty coil only in response to the transfer of an arc from the separating contacts to the arc chute.

2. An electromagnetic contactor according to claim 1, wherein said continuous-duty coil is a single-turn coil.

3. An electromagnetic contactor according to claim 1, wherein said means forming the current path includes a conductor having a portion thereof looped around said core, the looped portion of said conductor constituting said continuous-duty coil.

4. An electromagnetic contactor according to claim 3, wherein said conductor includes one end portion which forms a line terminal of the contactor, and an opposite end portion which has connected thereto station-ary contact means forming part of said separable contacts.

5. An electromagnetic contactor according to claim 1, wherein said intermittent-duty coil is a multiple-turn coil.

6. An electromagnetic contactor according to claim 1, wherein said arc chute comprises a lineside arc horn and a load-side arc horn which extend from spaced locations adjacent the contacts in diverging relationship with respect to each other, and the load-side arc horn of which is connected to said load terminal, said inter-mittent-duty coil being electrically connected between the continuous-duty coil and said line-side arc horn.

7. An electromagnetic contactor according to claim 1, wherein said arc blowout means includes a pair of ferromagnetic pole plates extending from opposite ends of said core to locations adjacent opposite sides of the arc chute.

8. An electromagnetic contactor according to claim 1 or 4 or 6, including an electromagnet having an armature which is movable to an actuated position upon energization of the electromagnet, thereby to close the separable contacts, and is biased to move to a dropout position upon de-energization of the electromagnet, there-by to open said contacts, an arm extending from said armature, and a resilient member biased toward a locking position with respect to said arm for preventing movement of the armature from said dropout position to said actu-ated position thereof, said arc chute being removable from the contactor and including a portion which cooperates with said resilient member to retain it against its bias in an ineffective position when the arc chute is in place, and to release the resilient member for movement thereof to said locking position when the arc chute is removed.

9. A contactor comprising stationary and movable contacts operable between open and closed posi-tions, mounting means for the movable contact, a conductor mounting the stationary contact, an arc chute adjacent to the contacts, arc blowout means for withdrawing an arc from between the contacts and comprising a first looped portion of the conductor and a ferromagnetic core in the looped portion, and said means also comprising a second intermittently rated looped conductor around the magnetic core and connected in series with the first looped portion only during arc interruption to effect an increase in the blowout magnetizing force.

10. The contactor of claim 9 in which the arc blowout means also comprises a pair of ferromagnetic pole piece plates, and each plate secured to the end of the magnetic core and extending to opposite sides of the arc chute to generate an increased magnetic field therebetween and within the arc chute.

11. The contactor of claim 10 in which the arc chute comprises a line arc horn and a load arc horn ex-tending from spaced locations near the contacts to diverg-ent locations, the contactor comprising a load terminal, and the load arc horn being connected to the load term-inal.

12. The contactor of claim 10 or 11 in which the load arc horn includes a lateral-extending member, an anti-close leaf spring biased by said member in a close position when the arc chute is mounted on the contactor, and an interlock arm on the armature extending across the end of the leaf spring when the armature is open to pre-vent closure of the armature when the arc chute is re-moved.