Information
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Patent Grant
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6225884
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Patent Number
6,225,884
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Date Filed
Tuesday, December 21, 199924 years ago
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Date Issued
Tuesday, May 1, 200123 years ago
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Inventors
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Original Assignees
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Examiners
- Donovan; Lincoln
- Nguyen; Tuyen T.
Agents
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CPC
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US Classifications
Field of Search
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International Classifications
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Abstract
A circuit breaker having a magnetic trip assembly includes a load terminal conductor having a first section, a second section, and a transition section connecting the first section and the second section, the transition section having a pair of faces lying in a plane generally perpendicular to a surface of the second section; a current transformer positioned around the second section of the load terminal conductor, the current transformer having a first side positioned generally parallel to the faces of transition section; and an insulating barrier positioned between the first side of the current transformer and the faces of the transition section of the load terminal conductor, the insulating barrier having a generally planar portion and a pair of leg portions extending from one edge of the generally planar portion, each leg portion lying along a side of the second section of the load terminal conductor and having a protrusion positioned adjacent a distal end thereof, each of said protrusions being positioned adjacent a bottom edge of the second section of the load terminal conductor. Insulating barriers for use in such circuit breakers are also included.
Description
BACKGROUND OF THE INVENTION
This invention is directed to electrical circuit breakers and, more particularly, to electrical circuit breakers having a trip mechanism including a magnetic device associated with a load terminal conductor.
Circuit breakers are generally old and well known in the art. Examples of circuit breakers are disclosed in U.S. Pat. Nos. 5,898,146 and 5,341,191. Such circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high-level short circuit condition.
Molded case circuit breakers include a pair of separable contacts per phase which may be operated either manually by way of a handle located on the outside of the case or automatically in response to an overcurrent condition. Circuit breakers include an operating mechanism which is designed to rapidly open and close the separable contacts, thereby preventing a moveable contact from stopping at any position which is intermediate between a fully open or a fully closed position. Circuit breakers also include a trip mechanism having a sensing device that senses overcurrent conditions in the automatic mode of operation; a trip bar responsive to the sensing mechanism; a trigger mechanism; and a latching and releasing mechanism. During an overcurrent condition, the trip bar responds to the sensing mechanism and releases the trigger mechanism. The trigger mechanism releases the latching and releasing mechanism, which, in turn, releases the operating mechanism thereby opening the separable contacts.
A typical sensing device is a current transformer positioned around a conductor that is connected to a load terminal of the breaker. It is desirable to prevent electrical contact between the current transformer and the adjacent conductor to prevent unwanted circulating currents in the current transformer components. Prior art circuit breakers have used an insulating barrier that included an opening for receiving the load terminal conductor. To install the barrier, the load terminal conductor had to be completely detached so that the barrier could be slid onto the conductor. It would be desirable to provide a circuit breaker with an insulating barrier that could be installed without the need to detach the load terminal conductor, but would still isolate the current transformer from the load terminal conductor.
SUMMARY OF THE INVENTION
A circuit breaker having a magnetic trip assembly includes a load terminal conductor having a first section, a second section, and a transition section connecting the first section and the second section, the transition section having first and second faces lying in a plane generally perpendicular to a surface of the second section; a current transformer positioned around the second section of the load terminal conductor, the current transformer having a first side positioned generally parallel to the face of transition section; and an insulating barrier positioned between the first side of the current transformer and the faces of the transition section of the load terminal conductor, the insulating barrier having a generally planar portion and a pair of leg portions extending from one edge of the generally planar portion, each leg portion lying along a side of the second section of the load terminal conductor and having a protrusion positioned adjacent a distal end thereof, each of said protrusions being positioned adjacent a bottom edge of the second section of the load terminal conductor. Insulating barriers, for use in such circuit breakers, are also included.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is an isometric view of the relevant portions of a circuit breaker constructed in accordance with this invention;
FIG. 2
is a longitudinal sectional view through the circuit breaker incorporating the invention;
FIG. 3
is an isometric view of selected elements of the circuit breaker of
FIG. 1
;
FIG. 4
is a plan view of the preferred embodiment of an insulating barrier used in the present invention;
FIG. 5
is a side elevation view of selected elements of the circuit breaker of
FIG. 1
; and
FIG. 6
is a top view of the load terminal conductor used in with the preferred embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings,
FIG. 1
is an isometric view of relevant portions of a circuit breaker
10
including a plurality of insulating barriers
12
,
14
,
16
and
18
constructed in accordance with the preferred embodiment of this invention. The circuit breaker includes a plurality of current transformers
20
,
22
,
24
, and
26
; each positioned around to a load terminal conductor. In this view, a portion of one of the load terminal conductors
28
is visible.
A trip unit serves to open the circuit breaker under certain conditions, and includes, for each phase, one of the current transformers for sensing load current. The current transformers are disposed about the load conductors and, in a manner well known in the art, detect current flowing through the separable contacts
30
,
32
,
34
and
36
. In the event of an excessive current in one of the load conductors, the current transformer associated with that load conductor will sense the excessive current and operate a actuator
38
that is coupled to a trip bar
40
. Movement of the trip bar results in the opening of the circuit breaker contacts in accordance with well-known techniques. The trip mechanism in this embodiment is constructed according to a known design, and the particular details of the trip mechanism are not important to the present invention. While the exemplary circuit breaker in
FIG. 1
includes four sets of contacts, it will become apparent that the modular construction of the circuit breaker is easily adaptable for assembling similar circuit breakers with fewer or more contact sets.
FIG. 2
is a side view, partially in section, of one of the poles of the circuit breaker of FIG.
1
. The circuit breaker
10
includes a molded housing
44
having a base section
46
and a cover (not shown). Each pole has a set of separable contacts
48
, which includes a fixed main contact
50
and a moveable main contact
52
. In addition, the separable contacts
48
include a fixed arcing contact
54
and a moveable arcing contact
56
. The fixed main contact
50
is mounted on a line side conductor
58
electrically connected to a line side terminal (not shown) for connection to an external circuit (not shown). The fixed arcing contact
54
is mounted on a conductor
60
electrically connected to the line side conductor
58
.
The moveable main contact
52
and moveable arcing contact
56
are mounted on a moveable conductor assembly
62
, which is connected by flexible shunts
64
to a load side conductor
66
, a terminal end of which serves as a load terminal. When the circuit breaker is closed as shown in
FIG. 2
, current from a source (not shown) connected to the line terminal (not shown) flows through the line side conductor
58
, the separable contacts
48
, the moveable conductor assembly
62
, the flexible shunts
64
, and the load side conductor
66
to a load (not shown).
The moveable conductor assembly
62
includes a contact arm
68
having a first or free end
70
and a second or supported end
72
. The contact arm is assembled from a stack of main contact arm laminations
68
and arcing contact laminations
74
. The moveable main contacts
52
are fixed to the free ends of the main contact arm laminations
68
, while the moveable arcing contacts
56
are affixed to the free ends of the arcing contact arm laminations
74
. As is known, the number of laminations is selected to provide the desired current rating for the circuit breaker.
Laminated contact arm
68
is supported by a contact arm carrier assembly
76
which in turn is rotatably mounted within the circuit breaker housing by a modular crossbar
78
. The spring powered latchable operating mechanism
80
is pivotally connected to the carrier assembly
76
at the center pole for moving the contact arms
68
, of all of the poles, between closed or open positions. Such spring powered operating mechanisms are well known in the art. A trip unit
82
, responds to current flowing through the circuit breaker sensed by the current transformer
20
to unlatch the spring powered latchable operating mechanism
80
in response to selectable current conditions. Unlatching of the latchable operating mechanism
80
by the trip unit
82
causes the operating mechanism to rotate the carrier assemblies
76
and therefore the contact arms
68
to a “tripped” position to open the separable contacts and interrupt the load current.
FIG. 3
is an isometric view of selected components of the circuit breaker of
FIGS. 1 and 2
. In this view, the load terminal conductor is shown to include an offset portion
106
with the current transformer
20
being positioned around the load terminal conductor at a location adjacent to the offset portion. An insulating barrier
12
is positioned between the current transformer and the offset portion of the conductor to prevent electrical contact between the side of the current transformer and the offset portion of the conductor. Such contact would create unwanted circulating currents in the transformer.
FIG. 4
is a plan view of the preferred embodiment of an insulating barrier
12
used in the present invention. The insulating barrier is shown to include a generally planar portion
84
, and a pair of legs
86
and
88
extending from one edge of the generally planar portion. Each of the legs includes a protrusion
90
,
92
adjacent to one end thereof. The legs create an opening
94
for receiving a portion of the load terminal conductor having a generally rectangular cross section. The legs have sufficient length to extend beyond the sides of the conductor, so that the protrusions can latch on to the bottom surface of the conductor, thereby coupling the insulating barrier to the conductor. A score line
96
is provided in the generally planar portion of the barrier. This score line is aligned with an outer edge of one of the legs and permits easy removal of the section
98
of the planar portion that extends beyond the leg
88
. By removing section
98
, the barrier can be used on end poles of the breaker.
FIG. 5
is a side elevation view of the insulating barrier
12
of
FIG. 4
positioned on a load conductor in a location that prevents contact of the sides of a current transformer with the conductor. The load conductor is seen to have a first section
100
, a second section
102
and a transition section
104
that connects the first and second sections to form a bend, or offset, portion
106
. As can be seen in
FIG. 3
, the transition portion of the load terminal conductor is slightly wider than the width of the second portion of the conductor. This results in a face
108
in a plane that is generally perpendicular to the top of section
102
. A similar face is formed on the side of the conductor that is opposite to that shown in FIG.
5
. Current transformer
20
is positioned around section
102
to detect the magnetic field resulting from current flowing in the load conductor. Insulation in the form of an insulating tape
110
is provided around the second section of the load conductor in the vicinity of the current transformer to prevent electrical contact between the walls of an interior aperture of the current transformer and section
102
of the load conductor. One side
112
of the current transformer lies generally parallel to face
108
.
It is desirable to prevent electrical contact between the side
112
of the current transformer and the transition section of the load conductor. This prevents unwanted circulating currents from flowing in the current transformer lamination stack. Such electrical contact is prevented by an insulating barrier
12
positioned between the side of the current transformer and the face
108
of the load current conductor. One of the legs of the insulating barrier
86
extends along the side of section
102
of the load conductor. In this position, the projections
90
and
92
of the insulating barrier, as shown in
FIG. 4
, extend under the bottom surface of load conductor section
102
, thereby latching the insulating barrier into place. With the particular insulating barrier structure shown in
FIG. 3
, the insulating barrier can be positioned onto the load conductor without having to disengage the conductor from its connection to the remainder of the circuit breaker. A breaker cover
114
is shown to have an interference fit at area
116
with the upper portion of the insulating barrier, further preventing movement of the barrier once it has been installed.
FIG. 6
is a top view of a load terminal conductor used in the preferred embodiment of the invention. In this view, the second section
102
of the conductor
28
is seen to have a smaller width than the transition portion
104
. This creates faces
108
and
118
that lie in a plane generally perpendicular to the surface of the second section
102
of the conductor. When the insulating barrier is installed, the legs of the barrier lie adjacent to these faces and between these faces and the side of the current transformer.
While a specific embodiment of the invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
Claims
- 1. An insulating barrier for use in an electric circuit breaker, the insulating barrer comprising:a generally planar portion and a par of leg portions extending from one edge f the generally planar portion and lying in a plane common with the generally planar portion, the leg portions defining an opening and each leg portion having a protrusion positioned adjacent a distal end thereof, wherein the protrusion extends toward the opening; wherein the planar portion includes a first section and a second section, the first section extending laterally beyond a first one of the leg portions and the second section extending literally beyond a second one of the leg portions; and further comprising a score line in the planar portion, the score line being aligned with one of the leg portions and lying adjacent to the first section of the planar portion.
US Referenced Citations (8)