Patent Description:
In a self-contained switching device such as a circuit breaker with an electronic trip unit (ETU), features are sometimes added to prevent closing the device and completing the primary circuit. These are often user-configurable features of the ETU that protect against closure if the closure would cause an unsafe condition. A simple example of an unsafe condition is a ground fault or other overcurrent condition. As another example, in power delivery systems that supply two loads from two power sources in a main-tie-main configuration, closing the system's tie breaker when the sources are not well-matched in voltage, frequency or phase could cause damage to system components. If the tie breaker's ETU detects such a mismatch, or if a remote controller that is monitoring the system detects the mismatch, the ETU or remote controller may respond by blocking any attempts to close the tie breaker.

Configurations in which the ETU or remote controller prevents closing are effective when the close command is initiated electronically, such as by a remote or local electrical actuator. In such situations, the system's programming may prioritize a "block closure" command over a command to close the switch. However, such configurations are not effective to block closure when closure is initiated locally by physical action, such as by an operator who depresses a mechanical pushbutton to manually operate the switch. This ineffectiveness occurs because electronic logic cannot intervene in the direct mechanical actuation of the circuit breaker mechanism. In order to prevent closing, the circuit breaker's ETU would need to operate the trip actuator and override the closing attempt, but trip actuators are typically intermittent operation devices and are not always maintained in an active state. Further, the trip actuators of some circuit breakers cannot mechanically operate to stop a close attempt when the circuit breaker is open. This is because the circuit breaker mechanism holds the trip actuator mechanism in the reset position whenever the switch is open. Further, ETUs of prior art circuit breakers typically will not detect when closure starts, but instead will only detect when the breaker's contacts touch, at which point it will have been too late to prevent the closure from happening. Even a few milliseconds of closure could damage system components and/or create safety hazards in overcurrent or voltage mismatch conditions.

This document describes an improved switching mechanism that is designed to help prevent closure of a switching device, even if the closure is initiated manually, when closure could result in an unsafe condition.

In <CIT> there is disclosed a cercuit breaker as it is defined in the pre-characterizing portion of claim <NUM>.

In various embodiments, a circuit breaker includes a moveable contact, an opening spring that is operably connected to the moveable contact, and a sensor that operates as a full open sensor. The sensor exhibits a first output condition when the moveable contact is in a fully open position, and it exhibits a second output condition when the moveable contact leaves the fully open position. An electronic trip unit (ETU) is electrically connected to the sensor and, when in a close break mode, blocks the circuit breaker from closing. The ETU does this by, in response to detecting that the sensor is in the second output condition (which corresponds to the moveable contact leaving the fully open position), generating a signal that will cause the opening spring to return the moveable contact to the fully open position.

The circuit breaker includes a trip actuator. The circuit breaker also includes an opening latch that, when in a latched position, will hold a linkage in a position which allows closing, and which thus holds the opening spring in a loaded position. In these embodiments, to cause the opening spring to return the moveable contact to the fully open position unit, the ETU's signal may cause the trip actuator to release the opening latch. Releasing the opening latch will allow the linkage to move and permit the opening spring to return to an unloaded condition. When the opening spring returns to its unloaded condition, the moveable contact will return to the fully open position. Optionally, the trip actuator may include a plunger having a retracted position and an extended position. The extended position may be operably connected to the opening latch. When the trip actuator receives the signal from ETU, the trip actuator will cause the plunger to move from the retracted position to the extended position and thus release the opening latch. When the moveable contact returns to the fully open position, the trip actuator will be reset.

The circuit breaker includes a moveable arm that is operably connected to the moveable contact, and may include axle that is operably and rotatably connected to the moveable arm. The circuit breaker also may include a linkage that operably connects the opening spring with the moveable arm via the axle, along with an extended member (such as a cam) that is connected to the axle. The sensor may be positioned to detect the extended member when a position of the moveable contact corresponds to the fully open position. Alternatively, the sensor may be configured to detect a rotational position of the axle.

Other embodiments are directed to a method of operating a circuit breaker that has a moveable contact, an opening spring, a sensor and an ETU. The method includes, by the sensor, detecting that the moveable contact is in a fully open position. After the sensor initially detects that the moveable contact is in the fully open position, the sensor may detect that the moveable contact has moved away from the fully open position. When this happens, then in response the sensor will change from a first output condition to a second output condition (such as from off to on, or from on to off). When the ETU detects that the sensor has changed to the second output condition, then in response it will cause the opening spring to return the moveable contact to the fully open position.

The circuit breaker also includes an opening latch that is operably connected to the opening spring. Causing the opening spring to return the moveable contact to the fully open position may be effected as the ETU causes the opening latch to release, which in turn causes the opening spring to relax (i.e., return to an unloaded condition). The opening spring may be operably connected to a lever that is operably connected to an axle, and the moveable contact is operably connected to a moveable arm that is also operably connected to the axle. In such a case, causing the opening spring to retract to the unextended condition may turn the axle, turning the axle rotates the moveable arm, and rotating the moveable arm moves the moveable contact to the fully open position. The axle may include an extended member (such as a cam). Detecting that the moveable contact is in the fully open position may include detecting, by the sensor that the extended member has moved away from the sensor or that the extended member has moved over the sensor. Other sensors (such as a sensor that detects rotational position of the axle) may be used to detect whether the moveable contact has left the fully open position.

The circuit breaker also includes a trip actuator that includes a plunger having a retracted position and an extended position. The trip actuator may be operably connected to the opening latch when in the extended position. If so, then in the method, causing the opening latch to release may include, by the ETU, generating a signal causes the trip actuator to release the opening latch by extending the plunger from the retracted position to the extended position. In such embodiments, the moveable contact may be connected to a moveable arm; and returning the moveable contact to the fully open position may cause the plunger to move to the retracted position and reset the trip actuator.

The circuit breaker also includes a closing spring. Detecting that the moveable contact has moved away from the fully open position occurs in response to the closing spring generating a closing force that begins to move the movable contact toward a closed position. When the opening spring returns the moveable contact to the fully open position, the opening spring will do so after the release of the opening latch, which releases the linkage that connects the closing spring to the movable arm.

In other embodiments, a stored energy circuit breaker includes a moveable contact, and a sensor. The sensor is positioned to exhibit a first output condition when the moveable contact is in a fully open position, and to exhibit a second output condition when the moveable contact moves away from the fully open position.

The circuit breaker also may include an extended member that is positioned over the sensor which the moveable contact is in the fully open position, and that is not positioned over the sensor when the moveable contact leaves the fully open position. Alternatively, the extended member may be positioned over the sensor when the moveable contact is in any position other than the fully open position. Other methods of sensing the full open position may include continuous position sensors in place of the extended member interacting with a discrete sensor.

The circuit breaker includes an ETU that is electrically connected to the sensor and that is configured to, in response to detecting that the sensor is in the second output condition, cause the moveable contact to return to the fully open position. The circuit breaker also may include a trip actuator that is electrically connected to the electronic trip unit and that is configured to receive and implement a command to cause the moveable contact to return to the fully open position. The circuit breaker also may include an opening latch that is operably connected to the trip actuator. The circuit breaker also may include an opening spring that is operably connected to the opening latch and to the moveable contact. The opening latch may: (i) when latched, hold the opening spring in a loaded position; and (ii) when unlatched, permit the opening spring to return to an unloaded position.

As used in this document, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. As used in this document, the term "comprising" (or "comprises") means "including (or includes), but not limited to. " When used in this document, the term "exemplary" is intended to mean "by way of example" and is not intended to indicate that a particular exemplary item is preferred or required.

Other terms that are relevant to this disclosure will be defined at the end of this Detailed Description section.

This disclosure describes a circuit breaker that incorporates a full open sensor that is used to help prevent closure of the breaker in conditions in which a closure could create an unsafe condition.

<FIG> are block diagrams that illustrate certain components of a stored energy circuit breaker <NUM> such as may exist in the prior art. The circuit breaker is operable to make or break a circuit between a first conductor <NUM> and a second conductor <NUM>. The first conductor <NUM> is electrically connected to a moveable conductive arm <NUM> that includes a moveable contact <NUM>, and the second conductor <NUM> (which may be a fixed conductive arm) is electrically connected to a fixed contact <NUM>. The fixed contact <NUM> may be a conductive element that is electrically connected to the second conductor <NUM>, or the fixed contact <NUM> may simply be an area of the second conductor <NUM> that will touch the moveable contact <NUM> when the circuit breaker <NUM> is in a closed position. When the moveable contact <NUM> is moved down to touch the fixed contact <NUM>, the switch is closed and the circuit is made. When the moveable contact <NUM> is moved up and away from the fixed contact <NUM>, the switch is open and the circuit is broken. A mechanical linkage that includes various linkage elements 105a, 105b and 105c will move in response to actuation mechanisms to move the moveable contact <NUM> toward or away from the fixed contact <NUM>.

In a stored energy circuit breaker <NUM> such as that shown in <FIG>, the system will include various springs that operate to move the linkage and open, close or trip the breaker. <FIG>- 1ED illustrate these and other components of such a prior art circuit breaker at various stages of operation, moving from an open position to a closed position. These includes a closing spring <NUM> and an opening spring <NUM>, each of which is operably connected to a frame <NUM> at one end and to one or more linkages at the other end. Optionally, the closing spring <NUM> may be a compression spring as illustrated by the arrows illustrating a direction of compression force, while the opening spring <NUM> may be a tension spring as illustrated by the arrows showing a direction of expansion. However, this arrangement may be reversed, or both springs may be of the same type, or other springs may be used such as torsion springs.

<FIG> illustrates the breaker in an open position, ready to close in that the closing spring <NUM> is mechanically charged, such as by a motor or by human operation, and is held in its compressed position by a closing latch <NUM>. When a close signal releases closing latch <NUM>, <FIG> illustrates that the closing spring <NUM> decompresses (i.e., relaxes) and begins to directly or indirectly push against one or more elements of the mechanical linkage (i.e., elements 105a and/or 105b) that are operably connected to the moveable arm <NUM>. Another element of the mechanical linkage 105c is held fixed by an opening latch <NUM>. <FIG> illustrates that as the closing spring <NUM> further decompresses and pushes against the mechanical linkage elements 105a, 105b, the mechanical linkage elements 105a, 105b move the moveable arm <NUM> downward, which forces the moveable contact <NUM> toward the fixed contact <NUM>. Ultimately, as illustrated in <FIG>, the moveable contact <NUM> reaches and touches the fixed contact <NUM>, the mechanical linkage elements 105a, 105b have reached a stop position (illustrated by dot <NUM>), and the circuit is closed.

In the position shown in <FIG>, the closing spring <NUM> is fully discharged. In this closed position, the opening spring <NUM> has been stretched and is therefore charged. In this position, the opening latch <NUM> holds the links 105a, 105b of the mechanical linkage in the stop position <NUM> and keep the opening spring <NUM> in an outstretched position. The opening latch <NUM> may be moved to this position manually by a mechanical push-button, remotely by a solenoid, or by the trip actuator <NUM>. After closing is complete and the closing spring <NUM> has been fully discharged as shown in <FIG>, the closing spring <NUM> will be recharged (in this example, compressed), either automatically by motor activation or manually by operation of a compression mechanism, and the closing latch <NUM> will be moved to hold the closing spring <NUM> in the charged position while the links 105a, 105b of the mechanical linkage remain in the stop position <NUM>. This final position is shown in <FIG>.

<FIG> are block diagrams that illustrate components of the previously-described prior art circuit breaker as it moves from a closed position to a fully open position. In <FIG>, the circuit breaker begins to open as the trip actuator <NUM> is operated. The trip actuator <NUM> may include a magnetic latch that is released with an electrical pulse from the circuit breaker's electronic trip unit (ETU). When the magnetic latch in the trip actuator <NUM> is released, the plunger <NUM> of the trip actuator <NUM> may extend and drive a trip linkage 135a, 135b to move and release the opening latch <NUM>, which releases the opening spring <NUM> and allows it to recoil to its naturally retracted (i.e., relaxed) position. Releasing the opening latch <NUM> also removes constraints on the linkage elements 105a, 105b and 105c and decouples the closing spring <NUM> from the linkage elements 105a and 105b. The force of closing spring <NUM> may then be transferred to linkage element 105c, which can now move since the opening latch <NUM> is released. This allows linkage elements 105a and 105b to then move away from the stop position and allow this retraction of the opening spring <NUM>. As the opening spring <NUM> relaxes (in this example, expands toward the open position), it directly or indirectly moves a contact linkage <NUM> that rotates the axle <NUM>, which is rotatably connected to the moveable arm <NUM> and thus causes the moveable arm <NUM> to rotate, which pulls the moveable contact <NUM> away from the fixed contact <NUM>. (Note: In <FIG>, the closing spring <NUM> has not yet been recharged. However, this is merely an example. Recharging of the closing spring may occur before or after the opening operation of <FIG>.

In <FIG>, as the opening spring <NUM> continues to relax (i.e., unload), it continues to move the linkage <NUM>, which rotates the moveable arm <NUM> about the axle <NUM> and pulls the moveable contact <NUM> further away from the fixed contact <NUM> and toward a drive element 135b of the trip linkage. The drive element 135b is the section of the trip linkage that the trip actuator's plunger <NUM> previously pushed downward. Pulling the linkage <NUM> to the left in <FIG> rotates the axle <NUM>, which rotates the moveable arm <NUM> and causes the free end of the moveable contact <NUM> to move upward.

In <FIG>, the moveable contact <NUM> has moved into the fully open position and directly or indirectly caused the drive element 135b of the trip linkage to move up to reset the plunger <NUM> into the trip actuator <NUM>. At this point, if the closing spring <NUM> has not yet been recharged, it may be recharged by motor-driven or manual operation to end up in the position originally shown above in <FIG>. The opening latch <NUM> will also be moved to latch the breaker in the open position in preparation for the next closing operation as shown in <FIG>.

In the prior art embodiments shown in <FIG>, if the close latch <NUM> receives a command to release from a controller, the command can be overridden by circuitry or programming logic so that the close latch does not in fact release in certain conditions. However, prior art systems are not capable of stopping manual operation of the close latch. To address this, referring to <FIG> this disclosure proposes an enhanced close block method and mechanism in which the circuit breaker includes a full open sensor <NUM> that is electrically connected to the electronic trip unit (ETU) <NUM>. The ETU <NUM> may be a conventional ETU or a customized ETU. For example, the ETU may be a programmable device such as a processor that receives signals from one or more external components and uses those signals to determine whether to trip the trip actuator <NUM>. Alternatively, in this disclosure the term ETU also may refer to an electromechanical trip unit that includes current-sensitive and thermal-sensitive devices that determine when to actuate the trip actuator <NUM> and open the breaker. Optionally, the circuit breaker also may include a full close sensor <NUM>. As shown in <FIG>, the full open sensor <NUM> and full close sensor <NUM> may be switches, pressure sensitive or other sensors positioned near the axle <NUM> to which the moveable arm <NUM> is operably connected.

As shown in <FIG>, the axle <NUM> may be equipped with a rotatable extended member such as a pin, lever or cam <NUM> that is positioned to be detected by, and thus change the condition of (i.e., turn on or turn off), the full open sensor <NUM> when the shaft position rotates to the circuit breaker's fully-open position. It may change the condition of the full close sensor <NUM> when the axle <NUM> rotates to the circuit breaker's fully-closed position. The extended member may be positioned over the sensor when the breaker is in the fully-open position as shown in <FIG>. Alternatively, the extended member may be configured so that it is always positioned over the full open sensor unless the breaker is in the fully-open position. Either configuration will enable the sensor to quickly identify when the circuit breaker begins to move out of the fully-open position. The configuration of a full open sensor shown in <FIG> is only an example. As an alternative, a rotational position sensor <NUM> may detect the rotational position of the axle. Alternatively, the sensor may be a sensor that is positioned in a location where it can directly detect the location of the moveable contact, or where it may detect the length of the opening spring. Other sensor configurations are possible.

Returning to <FIG>, in this position the circuit breaker is ready to close. Under normal conditions (i.e., no detection of overcurrent, ground fault, power mismatch or other unsafe conditions) this breaker will operate according to the procedures discussed above for <FIG> and <FIG>. However, the ETU <NUM> in the example of <FIG> is operating to require close blocking, meaning that it will block the circuit breaker from closing and keep it open. The ETU <NUM> may do this in response to, for example, a current detector detecting an overcurrent condition, a thermal sensor detecting an overheated condition, or detection of a phase mismatch across two sides of a trip breaker of a main-tie-main system. If a human attempts to manually release the closing latch <NUM> when the ETU is requiring close blocking, the output of the full open sensor <NUM> will change (such as changing from an on signal to an off signal or no signal) as shown in <FIG>.

Upon detecting this change of condition of the full open sensor <NUM>, as illustrated in <FIG> the ETU will immediately send a signal to actuate the trip actuator <NUM>. As illustrated in <FIG> this signal causes the plunger <NUM> of the trip actuator to extend from a retracted position (as in <FIG>) to an extended position (as in <FIG>), which in turn moves the trip linkage elements 135a, 135b to release the opening latch <NUM>. Releasing the opening latch <NUM> releases the tension in the opening spring <NUM> and causes the opening spring <NUM> to retract toward an unextended position. The release of the linkage by the opening latch will decouple the closing spring from the linkage elements 135a, 135b, allowing the opening spring to open. Thus, even though the closing spring <NUM> began to expand and apply a force to close the breaker, the opening spring <NUM> will immediately contract and pull the breaker open and prevent it from fully closing, thus maintaining a gap between the moveable contact <NUM> and the fixed contact <NUM>.

The breaker may then return to the fully open position as shown in <FIG>. although the closing spring <NUM> will be fully discharged at this point (as shown in <FIG>). At this point the moveable contact <NUM> will reset the trip actuator <NUM>, the full open switch <NUM> may return to delivering a full open signal to the ETU <NUM>, the ETU <NUM> may cease signaling the trip actuator <NUM> to actuate, and the closing spring <NUM> may be recharged.

Thus, the incorporation of a full open switch into a stored energy (i.e., spring release) circuit breaker provides an improved closing prevention capability that can override not only an electronic signal, but also manual operation of the breaker's closing mechanism.

It should be noted that the incorporation of the embodiments described above will not necessarily prevent the moveable contact from starting to move in response to a manual close operation. However, it will prevent the moveable contact from touching the stationary contact and closing the circuit when the ETU is operating in a close block condition. An example sequence of operation is explained with reference to <FIG>. At position <NUM>, the circuit breaker is in a fully open position. When the breaker's closing latch is released, the moveable contact will move toward the stationary contact, and at position <NUM> the two contacts will touch, eventually coming to rest at a fully closed position at <NUM>. However, the fully open sensor will change its output when the moveable contact reaches position <NUM>, very shortly after the fully open condition is released and well before the contacts touch at <NUM>. For, example, the fully open sensor will actuate before the moveable contact moves halfway through its mechanical range of motion of the closing operation, and in many configurations it will actuate well before that point. By way of example, the fully open sensor may actuate when the moveable contact reaches approximately <NUM>% of its mechanical range of motion, approximately <NUM>% of its mechanical range of motion, approximately <NUM>% of its mechanical range of motion, approximately <NUM>% of its mechanical range of motion, or some other set position. Thus, there will be a short period of movement by the moveable contact between positions <NUM> and <NUM>. When the ETU detects the fully open sensor's change in signal at position <NUM>, the ETU will trigger the trip actuator, which releases the opening latch and causes the moveable contact to return to the fully open position at <NUM> rather than continue to move to positions <NUM> and <NUM>.

It should also be noted that the description above, and in particular the figures, describe only an example circuit breaker operation, with only the functional elements of a circuit breaker that are necessary to describe the invention shown. In practice, other arrangements may be used, and the figures' illustrations that show certain components as interconnected does not necessarily mean that the components physically contact each other. The use of the word "operably" connected in the description and claims denotes, as defined below, that the parts need not physically touch each other.

In this document, when terms such "first" and "second" are used to modify a noun, such use is simply intended to distinguish one item from another, and is not intended to require a sequential order unless specifically stated. The term "approximately," when used in connection with a numeric value, is intended to include values that are close to, but not exactly, the number. For example, in some embodiments, the term "approximately" may include values that are within +/- <NUM> percent of the value.

In this document, the term "connected", when referring to two physical structures, means that the two physical structures touch each other. Devices that are connected may be secured to each other, or they may simply touch each other and not be secured.

In this document, the term "operably connected", when referring to two physical structures, means operation (i.e., movement) of one structure will cause the other structure to responsively move. Operably connected structures may be physically connected to each other, or they may be indirectly connected via one or more intermediate structures.

In this document, the term "electrically connected", when referring to two electrical components, means that a conductive path exists between the two components. The path may be a direct path, or an indirect path through one or more intermediary components.

Claim 1:
A circuit breaker comprising:
a moveable arm (<NUM>) operably connected to a moveable contact (<NUM>);
a fixed contact (<NUM>);
a closing spring (<NUM>) operably connected to one or more linkages (105a, 105b) that are operably connected to the moveable arm (<NUM>) and configured to move the moveable contact (<NUM>) toward or away from the fixed contact (<NUM>);
an opening spring (<NUM>) that is operably connected to the moveable contact (<NUM>); and
a sensor (<NUM>) that is operable to exhibit a first output condition when the moveable contact (<NUM>) is in a fully open position and a second output condition when the moveable contact leaves the fully open position;
characterized by:
an opening latch (<NUM>) that, when in a latched position, will hold the one or more linkages (105a, 105b) in a position which allows closing of the moveable contact (<NUM>) and the opening spring (<NUM>) to reach a loaded position;
a trip actuator (<NUM>) coupled to a trip linkage (135a, 135b) and including a plunger (<NUM>) configured to drive the trip linkage, the plunger having a retracted position and an extended position, the trip actuator operably connected to the opening latch (<NUM>) when the plunger in the extended position; and
an electronic trip unit (<NUM>) that is electrically connected to the sensor (<NUM>) and that is configured to block the circuit breaker from closing by, in response to detecting that the sensor is in the second output condition indicating that the moveable contact (<NUM>) has left the fully open position, generating and sending a signal to actuate the trip actuator (<NUM>) immediately, the signal causing the plunger (<NUM>) to extend from the retracted position to the extended position and move the trip linkage (135a, 135b) to release the opening latch (<NUM>), wherein:
releasing the opening latch (<NUM>) releases tension in the opening spring (<NUM>) and causes the opening spring to return to a relaxed condition,
the releasing the opening latch (<NUM>) also removes constraints on the one or more linkages (105a, 105b) and decouples the closing spring (<NUM>) from the one or more linkages, and
the decoupling the closing spring (<NUM>) from the one or more linkages (105a, 105b) allows the opening spring (<NUM>) to retract and rotate the moveable arm (<NUM>) to open the moveable contact into the fully open position, thereby preventing the moveable contact from fully closing.