Note: Descriptions are shown in the official language in which they were submitted.
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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
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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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embodying the invention;
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
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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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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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