Information
-
Patent Grant
-
6747532
-
Patent Number
6,747,532
-
Date Filed
Monday, December 23, 200221 years ago
-
Date Issued
Tuesday, June 8, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 335 6
- 335 8
- 335 10
- 335 11
- 335 13
-
International Classifications
- H01H7500
- H01H7700
- H01H8300
-
Abstract
A neutral pole for a multipole circuit breaker is disclosed. The circuit breaker includes a housing, a plurality of contact arms for opening and closing an electrical circuit, and an operating mechanism for driving the contact arms. The neutral pole includes a neutral housing, a conduction path within the neutral housing having a neutral arm arranged to open and close the conduction path, a bias spring configured to exert a first bias moment on the neutral arm when the conduction path is closed, a spring support configured to support the bias spring, a rotor pivotally arranged within the neutral housing and configured to displace the neutral arm and to open the conduction path, and a drive pin configured to couple the rotor to the multipole circuit breaker. The spring support is fixedly arranged at the neutral housing. The rotor is responsive to the opening and closing action of the operating mechanism of the multipole circuit breaker.
Description
BACKGROUND OF THE INVENTION
The present disclosure relates generally to multipole circuit breakers, and particularly to neutral poles for use in multipole circuit breakers.
Multipole circuit breakers configured to protect multiphase electrical circuits are known in the electrical circuit protection industry. The variety of constructions of multipole circuit breakers include blow open and non-blow open contact arms, overcentering and non-overcentering contact arms, single contact pair arrangements with the contact pair at one end of a contact arm and a pivot at the other end thereof, double contact pair arrangements (referred to as rotary breakers) with a contact pair at each end of a contact arm and a contact arm pivot intermediate (typically centrally located between) the two ends, single housing constructions with the circuit breaker components housed within a single case and cover, and cassette type constructions (referred to as cassette breakers) with the current carrying components of each phase housed within a phase cassette and each phase cassette housed within a case and cover that also houses the operating mechanism. Multipole circuit breakers are generally available in two, three, and four pole arrangements, with the two and three pole arrangements being commonly used in two and three phase circuits, respectively. Four pole arrangements are typically employed on three phase circuits having switching neutrals, where the fourth pole operates to open and close the neutral circuit in a coordinated arrangement with the opening and closing of the primary circuit phases. Some fourth pole neutrals have identical constructions to the phase poles and are simply appended onto an outer pole by way of an extended crossbar or drive rod. The combination, however, of a phase pole construction and an extended drive rod typically results in less contact depression in the neutral pole due to the additional strain on the drive rod, the fourth pole neutral being that much further removed from the operating mechanism. To address the anticipated reduction in contact depression, design modifications within the circuit breaker may be employed. Other fourth pole neutrals have supplemental fourth pole operating mechanisms specifically arranged for operating only the fourth pole neutral. While a supplemental fourth pole operating mechanism is effective in controlling lost contact depression to due additional strain, it also typically involves higher complexity and cost compared to a construction without a supplemental operating mechanism. In view of present fourth pole neutral arrangements, it is desirable to have a fourth pole neutral that overcomes the above disadvantages.
SUMMARY OF THE INVENTION
In one embodiment, a neutral pole for a multipole circuit breaker is disclosed. The circuit breaker includes a housing, a plurality of contact arms for opening and closing an electrical circuit and an operating mechanism for driving the contact arms. The neutral pole includes a neutral housing, a conduction path within the neutral housing having a neutral arm arranged for opening and closing the conduction path, a bias spring configured to exert a first bias moment on the neutral arm when the conduction path is closed, a spring support configured to support the bias spring, a rotor pivotally arranged within the neutral housing and configured to displace the neutral arm and open the conduction path, and a drive pin configured to couple the rotor to the multipole circuit breaker. The spring support is fixedly arranged at the neutral housing. The rotor is responsive to the opening and closing action of the operating mechanism of the multipole circuit breaker.
In another embodiment, a multipole circuit breaker includes a main housing, a main conduction path having contact arms configured to open and close an electrical circuit, an operating mechanism configured to drive the contact arms, and a neutral pole. The neutral pole includes a neutral housing in fixed arrangement with the main housing, a neutral conduction path within the neutral housing having a neutral arm arranged to open and close the neutral conduction path, a bias spring configured to exert a first bias force on said neutral arm when said neutral conduction path is closed, a spring support configured to support the bias spring, a rotor pivotally arranged within said neutral housing and arranged to displace the neutral arm and to open the neutral conduction path, and a drive pin configured to couple the rotor to the operating mechanism. The spring support is fixedly coupled to the neutral housing. The rotor is responsive to the opening and closing action of the operating mechanism.
In a further embodiment, a method for opening a neutral pole of a multipole circuit breaker includes receiving an opening command at the neutral pole from the multipole circuit breaker, and responding to the opening command to open the neutral conduction path by rotating a neutral rotor a first angular displacement under no load from a set of neutral bias springs and a second angular displacement under load from the set of neutral bias springs.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring to the exemplary drawings wherein like elements are numbered alike in the accompanying Figures:
FIG. 1
is an exemplary multiphase circuit breaker for use in an embodiment of the invention;
FIG. 2
is an isometric view of one phase of the exemplary multiphase circuit breaker of
FIG. 1
;
FIG. 3
is the exemplary multiphase circuit breaker of
FIG. 1
having a neutral pole in accordance with an embodiment of the invention:
FIG. 4
is an isometric view of the neutral pole of
FIG. 3
;
FIG. 5
is an exploded assembly view of several components of the neutral pole of
FIG. 3
;
FIG. 6
is an isometric view of an exemplary rotor and contact arm arrangement in accordance with an embodiment of the invention; and
FIG. 7
is a side view of an exemplary neutral pole of an embodiment of the invention in both the closed and open positions.
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the invention provides a multipole circuit breaker with a fourth neutral pole that is actuated by the operating mechanism of the main circuit breaker. While the embodiment described herein depicts a neutral pole as an exemplary fourth pole neutral, it will be appreciated that the disclosed invention is also applicable to other multipole circuit breakers that require the functionality of an auxiliary switching pole herein disclosed, such as two-pole circuit breaker or switch with auxiliary third pole for a control circuit for example.
An exemplary multipole circuit breaker
100
is depicted in
FIG. 1
having a base
110
and a cover
120
. Within base and cover
110
,
120
are cassettes
200
(discussed below in reference to
FIG. 2
) that provide a main housing for electrical conductors and circuit interrupters. An operating mechanism
140
for turning circuit breaker
100
ON and OFF includes an operating handle
150
that protrudes through aperture
160
of cover
120
, and a drive pin
170
for driving a set of contact arms
180
of a main conduction path
190
that is best seen by now referring to FIG.
2
. An embodiment of circuit breaker
100
is arranged with conduction path
190
housed within a cassette
200
, but the present invention is not limited to the use of a cassette-type construction. Main conduction path
190
includes a contact arm
180
with movable contacts
210
,
215
at opposite ends thereof, a line strap
220
, a line contact
225
, a load strap
230
, and a load contact
235
. When circuit breaker
100
is connected to an electrical circuit via connectors (not shown) on line and load straps
220
,
230
and is turned ON, the electrical current flows through line strap
220
, line contact
225
, movable contact
210
, contact arm
180
, movable contact
215
, load contact
235
, and load strap
230
. Operating mechanism
140
opens and closes conduction path
190
by rotating drive pin
170
about axis
240
, which in turn drives contact assembly
250
for ON/OFF actuation of contact arm
180
. Mechanism links
255
connect contact assembly
250
to operating mechanism
140
. A further description of the operating characteristics of exemplary circuit breaker
100
is disclosed in commonly assigned U.S. Pat. No. 6,114,641 entitled “Rotary Contact Assembly for High Ampere-Rated Circuit Breakers” filed May 29, 1998.
A neutral pole
300
, best seen by now referring to
FIG. 3
, is connected to cassettes
200
of circuit breaker
100
via fasteners
305
, such as rivets, bolts, or the like. Operating mechanism
140
of circuit breaker
100
serves to operate both circuit breaker
100
and neutral pole
300
. Drive pin
170
is coupled to operating mechanism
140
via mechanism links
255
and delivers the rotational moment about common pivot
310
when operating mechanism
140
is actuated.
Referring now to
FIG. 4
, an alternative view of neutral pole
300
with a side cover removed is depicted having a neutral housing
315
(minus the side cover), a neutral conduction path
320
, a spring support
325
fixedly coupled to neutral housing
315
by an interlocking projection and hole, or any other suitable means, a rotor
330
pivotally arranged within neutral housing
315
about common pivot
310
, and drive pin
170
for coupling rotor
330
to operating mechanism
140
as discussed above. Through drive pin
170
, rotor
330
is responsive to the opening and closing action of operating mechanism
140
.
Neutral conduction path
320
includes a neutral line strap
335
, a flexible conductor
340
, such as copper braid for example, a neutral arm
345
pivotally arranged at common pivot
310
and arranged for opening and closing neutral conduction path
320
, a neutral movable contact
350
, a neutral fixed contact
355
, and a neutral load strap
360
. When operating mechanism
140
is turned ON, neutral current, when present, passes through neutral line strap
335
, flexible conductor
340
, neutral arm
345
, neutral movable contact
350
, neutral fixed contact
355
, and neutral load strap
360
. Connectors (not shown) connect neutral line and load straps
335
,
360
to neutral circuit (not shown). When operating mechanism
140
is turned OFF, drive pin
170
acts upon rotor
330
to displace neutral arm
345
and open neutral conduction path
320
, as will be discussed in more detail below in reference to FIG.
6
.
Referring now to
FIG. 5
, an exploded assembly view of neutral conduction path
320
, spring support
325
, and rotor
330
is depicted. Neutral arm
345
includes four neutral arm links
365
(three are shown and one is hidden behind neutral arm
345
), each neutral arm link
365
has two holes
370
,
375
, one at each end. A first hole
370
is pivotally coupled to neutral arm
345
by a pivot pin
380
, and a second hole
375
is for receiving a translational spring anchor pin
390
(see also FIG.
4
). Bias springs
395
, depicted as tension springs, have one end anchored to a non-translational spring anchor pin
385
and the other end anchored to a translational spring anchor pin
390
. Bias springs
395
provide a bias force to bias neutral arm
345
in the ON direction to close neutral conduction path
320
, and are supported by spring support
325
. Non-translational spring anchor pins
385
are received in non-translational slots
400
on spring support
325
, and translational spring anchor pins
390
are received in translational slot
405
on spring support
325
. Slots
400
,
405
permit rotation of pins
385
,
390
, but only translational slots
405
permit translation of translational spring anchor pins
390
. After bias springs
395
are assembled to spring anchor pins
385
,
390
, and spring anchor pins
385
,
390
are assembled to spring support
325
as discussed above, rotor
330
is placed over spring support
325
and common pivot pin
410
is assembled through common pivot holes
415
,
420
,
425
.
The opening action of neutral arm
345
is best seen by now referring to
FIG. 6
, which depicts a portion of neutral conduction path
320
, specifically showing neutral arm
345
, and a portion of main conduction path
190
, specifically showing contact arm
180
of circuit breaker
100
. Also shown is a phase rotor
252
of circuit breaker
100
and rotor
330
of neutral pole
300
. Phase rotor
252
has an engagement surface
253
, which engages pickup surface
182
on contact arm
180
, and rotor
330
has an engagement surface
332
, which engages pickup surface
347
on neutral arm
345
, when operating mechanism
140
drives circuit breaker
100
and neutral pole
300
to the OFF position. The distance between engagement surface
332
and pickup surface
347
at neutral pole
300
is depicted as dimension “A”. The distance between engagement surface
253
and pickup surface
182
at circuit breaker
100
is depicted as dimension “B”. In an embodiment of the invention, dimension “A” is greater than dimension “B”, resulting in contact arm
180
being picked up before neutral arm
330
is picked up as operating mechanism
140
drives drive pin
170
and rotors
252
,
330
to the OFF position, which results in delayed opening of neutral contacts
350
,
355
. In one aspect of the invention, neutral arm
345
is not picked up until contact arm
180
has opened far enough to establish an air gap between contact pairs
210
,
225
and
215
,
235
of circuit breaker
100
. In the direction of closing, contact pairs
210
,
225
and
215
,
235
of circuit breaker
100
will make contact subsequent to the neutral contact pair
350
,
355
. In this manner, the fourth pole neutral
300
is considered to be of a first to make and last to break construction, which enables the neutral circuit to be closed when switching the main phase circuits.
Referring now to
FIGS. 4-6
collectively, rotor
330
is in a first orientation when neutral conduction path
320
is closed and gap “A” is at its maximum, in a second orientation when engagement surface
332
picks up pickup surface
347
and gap “A” is at zero, and in a third orientation when neutral conduction path
320
is open. When rotor
330
is between the first orientation and the second orientation, rotor
330
has not yet picked up neutral arm
345
and therefore rotor
330
does not experience any force feedback from bias spring
395
through neutral arm
345
to rotor
330
, that is, the spring force of bias spring
395
Is not transmitted through neutral arm
345
to rotor
330
. Alternatively, when rotor
330
is between the first and second orientations, bias spring
395
is isolated from rotor
330
. Under this no-load condition, rotor
330
is referred to as being in a free-wheel mode, which reduces the strain on drive pin
170
. When rotor
330
is between the second orientation and the third orientation, rotor
330
has picked up neutral arm
345
and therefore does experience a force being fed back from bias spring
395
through neutral arm
345
to rotor
330
, that is, the spring force of bias spring
395
is transmitted through neutral arm
345
to rotor
330
. Alternatively, when rotor
330
is between the second and third orientations, bias spring
395
is coupled to rotor
330
. In this second condition, rotor
330
is referred to as being in a loaded condition.
The spring bias moment exerted on closed neutral arm
330
and open neutral arm
330
′ by bias spring
395
and neutral links
365
is best seen by now referring to
FIG. 7
, which depicts closed neutral arm
330
in solid line fashion and open neutral arm
330
′ in phantom line fashion. For clarification, bias spring
395
is not shown in
FIG. 7
, however, it is readily understood from the description above that bias spring
395
is anchored between non-translational spring anchor pin
385
and translational spring anchor pin
390
. As neutral arm
330
pivots counterclockwise about common pivot
310
in fixed spring support
325
, translational spring anchor pin
390
translates along translational slot
405
to the position depicted by
390
′, resulting in a change in angle of neutral arm links
365
with respect to spring support
325
, and therefore a change in force vector, depicted by F
1
, F
2
. As a result, the closed moment M
1
, depicted by force F
1
and perpendicular distance X
1
, reduces by a predefined amount to produce the open moment M
2
, depicted by force F
2
and perpendicular distance X
2
. The reduced moment during opening is a result of distance X
2
reducing in magnitude at a faster rate than F
2
increases in magnitude. In one embodiment of the invention, the closed moment M
1
is greater than the open moment M
2
, and both moments bias neutral arm
330
to the closed position. It will be appreciated that other embodiments may employ other open and closed moments without detracting from the scope of the invention. As shown in
FIGS. 6 and 7
, neutral arm
330
can pivot about common pivot
310
independent of rotor
330
, thereby enabling neutral arm
330
to blow open for effective interruption when blow open current conditions exist in the neutral pole
300
.
An embodiment of neutral pole
300
opens according to the following procedure. The actuation of operating mechanism
140
in the OPEN direction results in a clockwise rotation (viewed from
FIG. 6
) of drive pin
170
about common pivot
310
, which provides the opening command received at neutral pole
300
. In response to the opening command, rotor
330
rotates a first angular distance to close the gap “A” (seen in
FIG. 6
) at which point engagement surface
332
on rotor
330
engages pickup surface
347
on neutral arm
345
, and then a second angular distance that separates neutral movable contact
350
away from neutral fixed contact
355
until neutral pole
300
is fully open. During the first angular displacement of rotor
330
, the spring load of bias springs
395
is self contained within spring support
325
, thereby resulting in a no load condition at rotor
330
as gap “A” closes with neutral conduction path
320
closed. This no load condition is also referred to as a free-wheel condition. During the second angular displacement of rotor
330
, the spring load of bias springs
395
is transmitted through translational spring anchor pin
390
, neutral arm link
365
, and neutral arm
345
to rotor
330
via pickup surface
347
and engagement surface
332
, thereby resulting in a loaded condition at rotor
330
as rotor
330
opens neutral conduction path
320
. In an embodiment where gap “A” is greater than gap “B”, rotor
330
will pickup neutral arm
345
via surfaces
332
,
347
and open neutral conduction path
320
after circuit breaker contact pairs
210
,
225
and
215
,
235
have opened in response to operating mechanism
140
.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.
Claims
- 1. A method for opening a neutral pole of a multipole circuit breaker, comprising:receiving an opening command at the neutral pole from the multipole circuit breaker; and responding to the opening command to open the neutral conduction path by rotating a neutral rotor a first angular displacement under no load from a set of neutral bias springs and a second angular displacement under load from the set of neutral bias springs.
- 2. The method of claim 1, wherein said responding to the opening command further comprises:rotating the neutral rotor the first angular displacement with the neutral conduction path closed; and rotating the neutral rotor the second angular displacement with the neutral conduction path open.
- 3. The method of claim 2, wherein said rotating the neutral rotor the second angular displacement further comprises:rotating the neutral rotor beyond the point that neutral conduction path opens subsequent to the opening of the main contacts of the multipole circuit breaker by an operating mechanism.
- 4. A neutral pole for a multipole circuit breaker, the circuit breaker having a housing, a plurality of contact arms for opening and closing an electrical circuit and an operating mechanism for driving the contact arms, the neutral pole comprising:a neutral housing; a conduction path within said neutral housing leaving a neutral arm arranged to open and close said conduction path; a bias spring configured to exert a first bias moment on said neutral arm when said conduction path is closed; a spring support configured to support said bias spring, said spring support being fixedly arranged at said neutral housing; a rotor pivotally arranged within said neutral housing and configured to displace said neutral arm and open said conduction path; and a drive pin configured to couple said rotor to the multipole circuit breaker, said rotor being responsive to the opening and closing action of the opening mechanism of the multipole circuit breaker; wherein said rotor is in a first orientation when said conduction path is closed, a second orientation when said rotor makes contact with said neutral arm when opening, said conduction path, and a third orientation when said conduction path is open, said bias spring exerting a bias force on said neutral arm that is not transmitted to said rotor when said rotor is between said first and second orientations, and said bias spring exerting a bias force on said neutral arm that is transmitted to said rotor when said rotor is between said second and third orientations.
- 5. The neutral pole of claim 4, wherein said neutral arm opens subsequent to the opening of the plurality of contact arms of the multipole circuit breaker and closes prior to the closing of the plurality of contact arms of the multipole circuit breaker during an opening and closing action, respectively.
- 6. The neutral pole of claim 4, further wherein said bias spring exerts a second bias moment on said neutral arm when said conduction path is open, said first bias moment being of greater magnitude than said second bias moment.
- 7. The neutral pole of claim 6, further wherein said first and second bias moments are both in a direction for closing said conduction path.
- 8. The neutral pole of claim 4, wherein said spring support further comprises a plurality of non-translational slots and a plurality of translational slots, the neutral pole further comprising:a first spring anchor pin pivotally received at said plurality of non-translational slots; a second spring anchor pin pivotally and translationally received at said plurality of translational slots; a plurality of neutral arm links each having a first hole at one end and a second hole at an opposite thereof, said first hole being pivotally coupled to said neutral arm and said second hole for receiving said second spring anchor pin; and a plurality of said bias springs arranged between said first and said second spring anchor pins.
- 9. The neutral pole of claim 4, wherein said neutral arm and said rotor have a common pivot pin, said common pivot pin being received at said spring support.
- 10. The neutral pole of claim 9, wherein said neutral arm is pivotally separable from said rotor.
- 11. A multipole circuit breaker, comprising:a main housing; a main conduction path having a plurality of contact arms configured to open and close an electrical circuit; an operating mechanism configured to drive said contact arms; and a neutral pole, comprising: a neutral housing in fixed arrangement with said main housing; a neutral conduction path within said neutral housing having a neutral arm arranged to open and close said neutral conduction path; a bias spring configured to exert a first bias force on said neutral arm when said neutral conduction path is closed; a spring support configured to support said bias spring, said spring support being fixedly coupled to said neutral housing; a rotor pivotally arranged within said neutral housing and arranged to displace said neutral arm and to open said neutral conduction path; and a drive pin configured to couple said rotor to said operating mechanism, said rotor being responsive to the opening and closing action of said operating mechanism; wherein said neutral arm opens subsequent to the opening of said plurality of contact arms and closes prior to the closing of said plurality of contact arms during an opening and closing action, respectively.
- 12. The multipole circuit breaker of claim 11, wherein said rotor of said neutral pole is in a first orientation when said neutral conduction path is closed, a second orientation when said rotor makes contact with said neutral arm when opening said neutral conduction path, and a third orientation when said neutral conduction path is open, said bias spring exerting a bias force on said neutral arm that is not transmitted to said rotor when said rotor is between said first and second orientations, and said bias spring exerting a bias force on said neutral arm that is transmitted to said rotor when said rotor is between said second and third orientations.
- 13. The multipole circuit breaker of claim 11, wherein said neutral arm and said rotor have a common pivot pin, said common pivot pin being received at said spring support.
- 14. The neutral pole of claim 13, wherein said neutral arm is pivotally separable from said rotor.
US Referenced Citations (23)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0 189 887 |
Jan 1992 |
EP |