Patent Grant
9966209
The invention relates to the field of circuit breakers. More specifically, the invention relates to a circuit breaker that includes an arc shield positioned on the escapement that motivates an arc off of the moveable contact.
Circuit interrupters are electrical components that can be used to break an electrical circuit, interrupting the current flow. A basic example of a circuit interrupter is a switch, which generally consists of two electrical contacts in one of two states; either closed, meaning that the contacts are touching and electricity can flow between them, or open, meaning that the contacts are separated, and no electricity can flow between them. A switch may be directly manipulated by a human to provide a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch.
Another example of a circuit interrupter is a circuit breaker. A circuit breaker may be used, for example, in an electrical panel to limit the electrical current being sent through the electrical wiring. A circuit breaker is designed to protect an electrical circuit from damage caused by an overload or a short circuit. If a fault condition such as a power surge occurs in the electrical wiring, the breaker will trip. This will cause a breaker that was in the “on” position to flip to the “off” position and shut down the electrical power leading from that breaker. When a circuit breaker is tripped, it may prevent a fire from starting on an overloaded circuit; it can also prevent the destruction of the device that is drawing the electricity.
A standard circuit breaker has a terminal connected to a power supply, such as a power line from a power company, and another terminal connected to the circuit that the breaker is intended to protect. Conventionally, these terminals are referred to as the “line” and “load” respectively. The line may sometimes be referred to as the input into the circuit breaker. The load, sometimes referred to as the output, feeds out of the circuit breaker and connects to the electrical components being fed from the circuit breaker.
A circuit breaker may be used to protect an individual device, or a number of devices. For example, an individual protected device, such as a single air conditioner, may be directly connected to a circuit breaker. A circuit breaker may also be used to protect multiple devices by connecting to multiple components through a power wire which terminates at electrical outlets, for example.
A circuit breaker can be used as a replacement for a fuse. Unlike a fuse however, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Fuses perform much the same circuit protection role as circuit breakers. However, circuit breakers may be safer to use in some circumstances than fuses, and may be easier to fix.
For example, in a situation where a fuse blows, interrupting power to a section of a building for example, it may not be apparent which fuse controls the interrupted circuit. In this case, all of the fuses in the electrical panel would need to be inspected to determine which fuse appears burned or spent. This fuse would then need to be removed from the fuse box, and a new fuse would need to be installed.
In this respect, circuit breakers can be much simpler to use than fuses. In a situation where a circuit breaker trips, interrupting power to a section of a building for example, it may be easily apparent which circuit breaker controls the interrupted circuit by looking at the electrical panel and noting which breaker has tripped to the “off” position. This breaker can then be simply flipped to the “on” position and power will resume again.
In general, a typical circuit interrupter has two contacts located inside of a housing. The first contact is stationary, and may be connected to either the line or the load. The second contact is movable with respect to the first contact, such that when the circuit breaker is in the “off” or tripped position, a gap exists between the first and second contact.
A problem with circuit interrupters that operate by separating contacts arises because the energized contacts separate when the circuit breaker is tripped, causing a gap to widen between the contacts while the movable contact moves from the closed position to the open position.
As the contacts begin to separate from the closed position, or approach complete closure from an open position, a very small gap exists between the contacts for a brief time while the contacts are closed or opened. An electric arc may be generated across this gap if the voltage between the contacts is high enough. This is because the breakdown voltage between the contacts is positively related to distance under pressure and voltage conditions in typical applications.
The creation of an arc during switching or tripping the circuit interrupter can result in undesirable side effects which can negatively affect the operation of the circuit interrupter, and which can create a safety hazard.
These effects can have consequences for the operation of the circuit interrupter. One possible consequence is that the arc may short to other objects in the circuit interrupter and/or to surrounding objects, causing damage and presenting a potential fire or electrocution safety hazard.
Another consequence of arcing is that the arc energy damages the contacts, causing some material to escape into the air as fine particulate matter. The debris which has been melted off of the contacts can migrate or be flung into the mechanism of the circuit interrupter, destroying the mechanism or reducing its operational lifespan.
Another effect of arcing stems from the extremely high temperature of the arc (tens of thousands of degrees Celsius) which can crack the surrounding gas molecules creating ozone, carbon monoxide, and other compounds. The arc can also ionize the surrounding gasses, potentially creating alternate conduction paths.
Because of these detrimental effects of arcing, it can be very important to quickly cool and quench the arc to prevent damage to the circuit interrupter.
Various techniques for transferring the arc away from the moveable contact are known. For example, it is known to provide arc transferring devices to draw an arc away from the contacts to limit the damage that may be done to the contact due to the heat buildup during the arcing process. However, since the arcing occur between the contacts, the devices known for drawing away the arcs have been positioned in the vicinity of the contact and typically on the moveable contact arm. However, a major disadvantage of this approach is that this adds weight (mass) to the moveable contact arm and that weight slows down the movement of the moveable contact arm as the heavier it is, the slower it will move with the same force applied to it. Even a relatively small (a few milliseconds) delay, can result is significant damage occurring to the contact as the heating caused by the arcing can severely damage the face of the contact.
Likewise, the arcing that occurs around the moveable contact can jump to the escapement and thereby heat and damage the escapement. This can be very serious because if the escapement is damaged too significantly, this can significantly slow the actuation of the moveable contact arm thereby causing still further damage to the system. Enough damage to the escapement can result in catastrophic failure opening mechanism.
Additionally, systems to draw an arc off of or away from the contacts can add significant cost and weight to the circuit interrupter. For example, an arm or other feature that may be positioned in close proximity to the moveable contact that may be positioned on the moveable contact arm may be used to draw and arch off of the moveable contact. However, this unfortunately, will add significant weight to the moveable contact arm. The increased mass will function to slow the operation of the contact arm. Even a small delay in opening the contacts can have a very large negative impact on the system.
It is therefore desired to provide an alternative system that is usable with a circuit interrupter that overcomes these limitations.
Accordingly, it is an object of the present invention to provide a circuit interrupter having a structure that functions to draw an arc that may develop in the gap between the contacts away from the contacts quickly and safely.
It is further desired to provide a system and method for protecting and shielding the escapement connected to the moveable contact arm when arcing occurs in a circuit interrupter when the contacts are opening.
It is further desired to provide a system and method for minimizing the arcing that occurs in a circuit interrupter that does not significantly impact the function, operation and cost of the circuit interrupter.
These and other objectives are achieved by providing a circuit interrupter that includes a first moveable contact and a second stationary contact that are movable into and out of contact with each other. The circuit interrupter further includes an escapement mechanically coupled to toward a first end of the moveable contact arm and the escapement coupled at another end to a handle. The moveable contact arm is still further mechanically connected at a second end to a linkage where the movement of the linkage is governed by an overcurrent device. An arc horn shield is connected to the escapement wherein an arc horn extends from the arc horn shield towards the moveable contact such that an arc that develops between the stationary contact and the moveable contact is drawn away from the moveable contact and onto the arc horn.
In one configuration, the arc horn extends from a side of the arc horn shield and comprises a substantially U-shaped extension. In this configuration, the arc horn essentially comprises a flat tab that is bent backward to create an arc receiving surface that, as the moveable contact opens, become essentially parallel with the moveable contact arm. As the moveable contact moves into the vicinity of the arc receiving surface, the arc is pulled toward the arc receiving surface from the moveable contact.
In another configuration, the arc horn is provided as a substantially flat U-shaped tab that extends from a lateral surface of the arc horn shield and is bent backwards upon itself. When the moveable contact arm is opened, the end of the moveable contact arm that holds the moveable contact moves into the vicinity of the arc horn and passes below the bottom portion of the U-shaped tab. Any arc that may be present on the moveable contact when opening will be transferred or drawn to the arc receiving surface of the arc horn.
A primary benefit of this configuration is that the arc horn shield may be provided as a robust device that is capable of handling a strong arc. One of the major difficulties that circuit interrupters face is that arc quenching devices must be robust (have sufficient mass) to withstand arcing and the associated damage that can occur due to the heat buildup caused by the arcing. However, when the size and weight of the arc quenching device is increased, this has a dramatic negative effect on the ability of the moveable contact arm to quickly and effectively open the contact to break the arc that may occur. So, arc quenching devices have been reduced in size and weight to minimize the negative effect on the moveable contact arm, but this in turn, has lowered the lifespan and effectiveness of the arc quenching device as the smaller and lighter weight devices are, 1) not as effective in motivating an arc off of the moveable contact; and 2) more subject to wear and damage. Additionally, the more wear and damage that occurs to the arc quenching device, the less effective the device becomes further exacerbating the problem. This problem is addressed, however, in the current configuration by positioning the arc horn shield not on the moveable contact arm, but rather, on the escapement.
By positioning the arc horn shield on the escapement, the mass (weight) of the moveable contact arm is not increased and therefore the speed in which the moveable contact can be opened is not negatively impacted. To achieve the benefits of motivating an arc that may form when opening the contact, the escapement needs to be positioned in such a manner that the moveable contact comes into close proximity with the escapement. This however, creates the potential that arcing and the heat associated therewith, may damage the escapement. Accordingly, the arc horn shield is formed in such a manner that it extends substantially around three sides of the escapement (the side facing the moveable contact and the two opposing lateral sides). By forming the arc horn shield in this manner, the escapement is substantially encased in the arc horn shield to prevent any damage from occurring due to potential arcing.
The arc horn shield can comprise any material that is highly conductive (e.g., essentially any type of metal or alloy material) and is coupled to ground so as to dissipate any arc that may be drawn onto the arc horn.
For this application the following terms and definitions shall apply:
The term “network” as used herein includes both networks and internetworks of all kinds, including the Internet, and is not limited to any particular network or inter-network.
The terms “first” and “second” are used to distinguish one element, set, data, object or thing from another, and are not used to designate relative position or arrangement in time.
The terms “coupled”, “coupled to”, “coupled with”, “connected”, “connected to”, and “connected with” as used herein each mean a relationship between or among two or more devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, and/or means, constituting any one or more of (a) a connection, whether direct or through one or more other devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, or means, (b) a communications relationship, whether direct or through one or more other devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, or means, and/or (c) a functional relationship in which the operation of any one or more devices, apparatus, files, programs, applications, media, components, networks, systems, subsystems, or means depends, in whole or in part, on the operation of any one or more others thereof.
In one embodiment, a circuit interrupter is provided comprising a set of contacts including a stationary contact and a moveable contact, and a contact arm having a first end and a second end, the moveable contact positioned at the first end. The circuit interrupter further comprises a linkage coupled to the second end of the contact arm, the linkage coupled to an overcurrent measurement device and to a handle. The circuit interrupter still further comprises an escapement coupled at a first end to the contact arm at a location between the first and second ends of the contact arm, the escapement coupled at a second end to the handle, wherein actuation of the handle causes the moveable contact arm to move to either open or close the set of contacts. Finally, the circuit interrupter comprises an arc horn shield mounted onto the escapement, the arc horn shield including an protrusion extending from a side portion thereof in the form of a tab that includes an arc receiving surface such that when the moveable contact arm is displaced to an open position, the moveable contact is moved into the vicinity of the arc receiving surface.
In another embodiment, a circuit interrupter is provided comprising a stationary contact, a moveable contact and a contact arm having a first end and a second end, the moveable contact positioned toward the first end. The circuit interrupter further comprises a handle and an escapement coupled at one end to a point along a length of the contact arm and at another end to the handle, wherein actuation of the handle causes the moveable contact arm to move the moveable contact into and out of physical contact with the stationary contact. The circuit interrupter still further comprises an arc horn shield mounted onto the escapement, the arc horn shield including an protrusion extending from a side portion thereof in the form of a tab that includes an arc receiving surface such that when the moveable contact arm is displaced to an open position, the moveable contact is moved into the vicinity of the arc receiving surface.
Other objects of the invention and its particular features and advantages will become more apparent from consideration of the following drawings and accompanying detailed description.
Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views.
Circuit interrupter 100 may be any device which can be used to make and break a circuit using contacts. For example, it will be clear to those having ordinary skill in the art that circuit interrupter 100 may be a simple switch, or may be implemented as a circuit breaker having a housing 102, for example. Housing 102 may include vents to allow gasses and debris produced by arcing to escape housing 102.
Circuit interrupter 100 includes a stationary contact 110 that is electrically connected to line terminal 120 through conductor 122. The line terminal receives electricity from a power source, such as, a generator (not shown), which in some applications is supplied by a power company.
Circuit interrupter 100 still further includes a moveable contact 112 mounted on moveable contact arm 130. The moveable contact 112 is positioned toward a first end 132 of the moveable contact arm 130. The moveable contact arm 130 further includes a second end 134 that is opposite the first end 132.
Moveable contact arm 130 is, in turn, connected to escapement 140, which includes a first end 142 and a second end 144. The first end 142 of escapement 140 is connected to the moveable contact arm at a location along a length of the moveable contact arm and preferably toward a mid-point 136 thereof.
The second end 144 of escapement 140 is connected to a handle 150 that extends from housing 102.
First movable contact 112 is connected to load terminal 124 through a conductor 126 to overcurrent measurement device 160 and through conductor 128. The overcurrent measurement device 160 may be any type of well-known device for measuring current that passes through the circuit interrupter 100. Once a maximum current is reach, the measurement device will function to cause the contact arm 130 to move to an open position. Likewise, the handle 150 will move to an intermediate position to indicate a “tripped” state of circuit interrupter 100.
Also illustrated in
The arc horn shield will now be discussed in connection with
As can be seen with reference to
Turning also now to
The function and operation of the circuit interrupter 100 including the arc horn shield 170 will now be discussed.
In
The moveable contact arm is rotated upward such that moveable contact 112 is moved away from stationary contact 110. In
In
Although the invention has been described with reference to a particular arrangement of parts, features and the like, these are not intended to exhaust all possible arrangements or features, and indeed many other modifications and variations will be ascertainable to those of skill in the art.
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