Patent Description:
Circuit interrupters, such as for example and without limitation, circuit breakers, are typically used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition, a short circuit, or another fault condition, such as an arc fault or a ground fault. Circuit breakers typically include separable contacts. The separable contacts may be operated either manually by way of an operator handle or automatically in response to a detected fault condition. Typically, such circuit breakers include an operating mechanism, which is designed to rapidly open and close the separable contacts, and a trip mechanism, such as a trip unit, which senses a number of fault conditions to trip the breaker automatically. Upon sensing a fault condition, the trip unit causes the operating mechanism to trip open the separable contacts.

Circuit breaker accessories such as shunt trip, spring release, and under voltage release devices can be operatively connected to a circuit breaker and used to open and close the separable contacts. A shunt trip assembly typically includes a conductive coil and armature operating mechanism that is coupled to the circuit breaker operating mechanism by a mechanical linkage such that movement in the shunt trip operating mechanism causes corresponding movement in the circuit breaker operating mechanism. The shunt trip assembly is additionally operatively coupled to a remote power source that is structured to energize the coil and actuate the shunt trip operating mechanism such that an operator at a remote location can open the circuit breaker separable contacts. An under voltage release device includes a conductive coil connected to a spring, wherein the coil requires a continuous power supply to maintain the spring in a position that keeps the separable contacts of circuit breaker closed and consequently trips the circuit breaker open when supply voltage to the under voltage release device drops below a threshold voltage. A spring release device comprises a coil and armature operating mechanism that causes a compressed spring to expand when the coil is energized by a voltage input and can remotely cause the operating mechanism of a circuit breaker to close the separable contacts by expanding the compressed spring.

As with any electrical or mechanical components, the components of circuit breaker accessory devices such as shunt trip, spring release, and under voltage release devices can malfunction and/or wear down. Malfunctioning and wearing down of the accessory devices can in turn prevent the circuit breaker from operating properly. When a circuit breaker fails to operate properly, determining whether the issue lies within the components of the circuit breaker or the components of a connected accessory device can be time-consuming and inefficient.

There is thus room for improvement in diagnostics systems for circuit breaker accessory devices.

Attention is also drawn to <CIT> which discloses an accessory device according to the preamble of claim <NUM>, and which is directed toward optimizing the operation and various functions of an undervoltage device by monitoring a solenoid for the purpose of activating an alarm (or de-energizing the device, if the user prefers) to alert the user when the solenoid fails to meet threshold requirements,.

Further, <CIT> is directed toward performing a signature analysis of the waveform of current passing through a DC trip coil of a circuit breaker in order to detect changes in the trip coil of the circuit breaker.

In accordance with the present invention, an accessory device and a method as set forth in claims <NUM> and <NUM>, respectively, are provided. Further embodiments are inter alia disclosed in the dependent claims.

A full understanding of the disclosed concept can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:.

Directional phrases used herein, such as, for example, left, right, front, back, top, bottom and derivatives thereof, relate to the orientation of the elements shown in the drawings and are not limiting upon the claims unless expressly recited therein.

As used herein, the singular form of "a", "an", and "the" include plural references unless the context clearly dictates otherwise.

As used herein, the statement that two or more parts or components are "coupled" shall mean that the parts are joined or operate together either directly or indirectly, i.e., through one or more intermediate parts or components, so long as a link occurs. As used herein, "directly coupled" means that two elements are directly in contact with each other. As used herein, "fixedly coupled" or "fixed" means that two components are coupled so as to move as one while maintaining a constant orientation relative to each other. As used herein, "movably coupled" means that two components are coupled so as to allow at least one of the components to move in a manner such that the orientation of the at least one component relative to the other component changes.

As employed herein, the term "number" shall mean one or an integer greater than one (i.e., a plurality).

As employed herein, the term "processor" shall mean a programmable analog and/or digital device that can store, retrieve and process data; a controller; a control circuit; a computer; a workstation; a personal computer; a microprocessor; a microcontroller; a microcomputer; a central processing unit; a mainframe computer; a mini-computer; a server; a networked processor; or any suitable processing device or apparatus.

<FIG> shows a schematic depiction of a smart accessory <NUM> structured to be operatively coupled to a protective relay or trip unit <NUM> of a circuit breaker according to an exemplary embodiment of the disclosed concept. For economy of disclosure, the protective relay or trip unit <NUM> will be referred to hereinafter as the trip unit <NUM>, but it will be appreciated that the trip unit <NUM> can instead or additionally comprise a protective relay without departing from the scope of the disclosed concept. The trip unit <NUM> trips open the separable contacts of the associated circuit breaker (not pictured) upon detection of a fault condition. Accessory <NUM> can be, for example and without limitation, a shunt trip, spring release, or under voltage release device structured to be used with the circuit breaker associated with the trip unit <NUM>.

Accessory <NUM> comprises a power section <NUM> and a control section <NUM>, the power section <NUM> and the control section <NUM> each containing electrical circuitry and being in electrical communication with and operatively coupled to one another. The control section <NUM> further comprises a processor <NUM>, which performs diagnostic functions for the accessory <NUM> as described in more detail herein with respect to <FIG> and <FIG>. In addition, circuit breaker accessory devices such as accessory <NUM> are often powered by external power sources, and the power section <NUM> is in direct electrical communication with an external power source <NUM>, while the control section <NUM> is in direct electrical communication with a communication bus <NUM> that enables communication between the accessory <NUM> and any other entity connected to the bus <NUM>.

Non-limiting examples of entities that can be connected to the bus <NUM> include the trip unit <NUM> (including the supervisory intelligence of the trip unit or protective relay) and a diagnostic interface <NUM> through which a user can receive information provided by the accessory <NUM> about the state of the accessory <NUM>. It will be appreciated that the schematic depiction of the accessory <NUM>, the trip unit <NUM>, and the diagnostic interface <NUM> in <FIG> is meant to be illustrative and is not intended to be limiting on the scope of the disclosed concept. For example, the diagnostic interface <NUM> is depicted as being a separate component from the trip unit <NUM>, but both the diagnostic interface <NUM> and the trip unit <NUM> can be included in the same physical structure housing the associated circuit breaker without departing from the scope of the disclosed concept.

For economy of disclosure, the power section <NUM> and the control section <NUM> are depicted in a simplified manner in <FIG>, as are the elements of the power section <NUM> schematically shown in <FIG>, and it will be appreciated that the elements of the power section <NUM> shown in <FIG> are illustrative and not intended to limit the scope of the disclosed concept. In particular, a current sensor <NUM> and a voltage sensor <NUM> are included in the power section <NUM> so that the control section <NUM> can monitor the current through and the voltage across the internal components of the power section <NUM>, but the specific implementations of the current sensor <NUM> and voltage sensor <NUM> shown in <FIG> are illustrative in nature and intended to be non-limiting. For example, the current sensor <NUM> is depicted as being in series between the power source <NUM> and an input terminal of an inductor L1 (which also represents an actuator <NUM> of the accessory <NUM> as described with respect to <FIG> herein), but the current sensor <NUM> can be placed elsewhere in the power section <NUM> and more than one current sensor can be included in the power section <NUM> without departing from the scope of the disclosed concept. In another example, the voltage sensor <NUM> is depicted as being in parallel with the series-connected actuator <NUM> (inductor L1) and MOSFET Q1, but the voltage across the actuator <NUM> can be measured using elements other than a MOSFET in series with the actuator <NUM> without departing from the scope of the disclosed concept.

Still referring to <FIG>, the actuating mechanism of the shunt trip, spring release, and under voltage release devices of accessory <NUM> includes a solenoid and plunger arrangement, such as the actuator <NUM> shown in <FIG>. Referring now to <FIG>, which show a cross-sectional view of a solenoid <NUM> and a plunger <NUM>, the solenoid <NUM> comprises a coil <NUM> of conductive wire wound around a bobbin and enclosed by a magnetic frame (the bobbin and frame not being numbered), with the ends of the coil structured to be electrically connected to a power source, such as the external power source <NUM>. The plunger <NUM> is produced from ferromagnetic material and is mechanically coupled to the solenoid <NUM>. When power is provided to the solenoid <NUM> and current flows through the coil <NUM>, a magnetic field is generated and actuates the plunger <NUM> to move in the direction indicated by the arrow <NUM>.

A load <NUM> can be coupled to the plunger <NUM>, such that the plunger <NUM> either acts as a pull-type plunger (shown in <FIG>) or a push-type plunger (shown in <FIG>) when actuated. For example, a solenoid <NUM> used in an under voltage release device is generally coupled to a pull-type plunger <NUM> as shown in <FIG>, while a solenoid <NUM> used in a shunt trip or spring release device is generally coupled to a push-type plunger <NUM> as shown in <FIG>. However, whether the type of plunger <NUM> coupled to a solenoid <NUM> included in an accessory <NUM> is a pull-type or push-type is not intended to limit the scope of the disclosed concept. In addition, an optional spring is sometimes coupled to the solenoid frame as well (as shown in <FIG>), particularly in under voltage release devices. In the context of circuit breaker accessory devices, if the accessory <NUM> is a shunt trip or under voltage release device, the load <NUM> coupled to the plunger <NUM> is generally a component that actuates the circuit breaker operating mechanism to open the separable contacts, and if the accessory <NUM> is a spring release device, the load <NUM> coupled to the plunger <NUM> is generally a component that actuates the circuit breaker operating mechanism to close the separable contacts.

The accessory <NUM> can only actuate the circuit breaker operating mechanism if the actuator <NUM> is operating properly, and a solenoid-based actuator such as actuator <NUM> can only operate properly if current is able to properly flow through the solenoid coil <NUM> and the plunger <NUM> is able to move in response to the magnetic field generated when current flows through the coil <NUM>. However, various conditions can cause a solenoid coil <NUM> to create a short circuit or conversely, to burn out and open such that current cannot flow through the coil <NUM>. In addition, in a solenoid-based actuator, a plunger <NUM> can become stuck and unable to move even when current is able to properly flow through the solenoid coil <NUM>. For example, solenoid bobbins can be produced from plastic, and if a high current flows through the solenoid coil <NUM> for too long, the heat of the current can melt the plastic of the bobbin and cause the plunger <NUM> to become stuck. In another example, if the shunt trip device is installed within the parent circuit breaker, the mechanical shock and/or vibration to which the parent breaker is subjected can cause the plunger to become stuck.

It is therefore an object of the present disclosure to provide diagnostic mechanisms (described in more detail with respect to <FIG> herein) that can alert a user in real time if any component of an actuator <NUM> is non-operational or failing (i.e. approaching a non-operational condition). The actuator <NUM> of the accessory <NUM> is depicted in <FIG> as comprising a solenoid <NUM> and a plunger <NUM>.

Referring to <FIG>, <FIG>, and in accordance with an exemplary embodiment of the disclosed concept, the processor <NUM> shown in <FIG> continually monitors the current flow through the actuator <NUM> while power is being supplied to the accessory <NUM> by executing a coil diagnostic <NUM>, represented by the flow chart shown in <FIG>, to determine the operating condition of the solenoid coil <NUM> at any given time and whether the coil <NUM> is failing or non-operational. At step <NUM> of diagnostic <NUM>, the external power source <NUM> applies power to the accessory <NUM>. At step <NUM>, the processor <NUM> checks whether the solenoid coil <NUM> has become open. <FIG> shows the accessory <NUM> shown in <FIG> with a coil <NUM> that has opened, and the processor <NUM> can detect an open circuit condition such as that shown in <FIG> when a current Icoil through the solenoid coil <NUM> (detected by the current sensor <NUM>) is less than a certain predetermined threshold current IopenTh deemed to be indicative of an open coil. When the coil <NUM> is open, the actuator <NUM> will never trip the circuit breaker since current is unable to flow through the coil <NUM> to actuate the plunger <NUM>, so if the processor <NUM> detects an open coil condition at step <NUM> of diagnostic <NUM>, the processor <NUM> reports the open coil condition by triggering an alarm at step <NUM>. The alarm can comprise, for example and without limitation, a sound notification such as a beep, a visual notification such as a toggled sticker display or an illuminated LED, or a notification sent to a remote device via wireless communication. It will be appreciated that the trip unit <NUM> can be programmed with software to have wireless communication (or other communication) capability, and that a trip unit <NUM> so programmed transmits a notification to the remote device after receiving a message from the processor <NUM> on the bus <NUM> indicating that an alarm condition exists.

Referring again to <FIG>, if an open coil condition was not detected at step <NUM>, then diagnostic <NUM> proceeds to step <NUM> and the processor <NUM> checks whether the solenoid coil <NUM> has shorted. <FIG> shows the accessory <NUM> shown in <FIG> with a coil <NUM> that has shorted, and the processor <NUM> can detect a short circuit condition such as that shown in <FIG> when the current Icoil through the solenoid coil <NUM> exceeds a certain predetermined threshold current IshortTh deemed to be indicative of a shorted coil. When the coil <NUM> is shorted, current flow through the coil <NUM> can reach levels damaging to the actuator <NUM>, so if the processor <NUM> detects a shorted coil condition at step <NUM> of diagnostic <NUM>, the processor <NUM> cuts off power to the actuator <NUM> and reports the shorted coil condition by triggering an alarm at step <NUM>.

Referring again to <FIG>, if a shorted coil condition was not detected at step <NUM>, then diagnostic <NUM> proceeds to step <NUM> and the processor <NUM> checks whether any individual turns of the solenoid coil <NUM> have shorted such that the coil <NUM> is partially shorted (as opposed to checking at step <NUM> whether the entire coil <NUM> has shorted). <FIG> shows the accessory <NUM> shown in <FIG>, with a coil <NUM> that has partially shorted. A partial short circuit condition occurs when only some of the turns of the coil <NUM> have shorted, rather than the entire coil <NUM>. In operation, sometimes only a few turns of a coil <NUM> fail at a time with successively more turns of the coil <NUM> failing over time, rather than all of the turns of the entire coil <NUM> shorting all at once. The current draw of the coil <NUM> increases as more turns short. The processor <NUM> can detect a partial short circuit condition such as that shown in <FIG> when the current Icoil through the solenoid coil <NUM> has increased relative to a previously executed cycle of diagnostic <NUM>. If the processor <NUM> detects a partially shorted coil condition at step <NUM> of diagnostic <NUM>, the processor <NUM> reports the shorted coil condition by triggering an alarm at step <NUM> so that a user can replace the coil <NUM> before enough turns become shorted to draw a damaging amount of current. If the processor <NUM> does not detect an open coil, shorted coil, or partially shorted coil after iterating through steps <NUM>, <NUM>, and <NUM> of diagnostic <NUM>, that cycle of diagnostic <NUM> is complete. The diagnostic <NUM> then returns to step <NUM> to execute another cycle until power to the accessory <NUM> is cut off.

Even if the coil <NUM> is in good operating condition as determined by running the coil diagnostic <NUM>, the accessory actuator <NUM> can still fail to trip the circuit breaker if the plunger <NUM> becomes stuck and cannot move when the coil <NUM> is energized. Referring to <FIG>, the processor <NUM> is configured to execute a plunger diagnostic <NUM> in the event that the accessory <NUM> fails to trip the circuit breaker when it should. The processor <NUM> determines that the accessory <NUM> failed to trip the circuit breaker when it should have based on information received from the circuit breaker over the communication bus <NUM>, and based on readings of the current sensor <NUM> and voltage sensor <NUM> indicating that power was provided to the accessory <NUM> for the purpose of tripping the circuit breaker.

Still referring to <FIG>, at step <NUM> of diagnostic <NUM>, the external power source <NUM> applies power to the accessory <NUM>. At step <NUM>, the processor <NUM> receives information from the circuit breaker, the current sensor <NUM>, the voltage sensor <NUM>, and/or other information sources indicating that the accessory <NUM> should have tripped the circuit breaker, and the processor <NUM> checks whether the accessory <NUM> initiated the required trip. If the processor <NUM> determines that the accessory <NUM> did trip the circuit breaker, the diagnostic <NUM> ends at step <NUM>. If the processor <NUM> determines that the accessory <NUM> failed to trip the circuit breaker, the diagnostic <NUM> proceeds to step <NUM> and checks whether the most recent measurement of Icoil through the solenoid coil <NUM> falls within a normal operating range. It will be appreciated that the processor can refer to the information being gathered during the concurrently running coil diagnostic <NUM> previously described with respect to <FIG> to determine whether Icoil falls within the normal operating range. If the processor <NUM> determines at step <NUM> that Icoil falls outside of the normal operating range, then the processor <NUM> reports the abnormal coil condition by triggering an alarm at step <NUM> that corresponds to the particular coil condition as detected according to the coil diagnostic <NUM>.

If the processor <NUM> determines at step <NUM> that Icoil falls within the normal operating range, then the diagnostic <NUM> proceeds to step <NUM> and the processor <NUM> checks whether the current signature of the solenoid coil <NUM> is indicative of movement by the plunger <NUM> in order to determine the operating condition of the plunger <NUM>, i.e. whether or not the plunger <NUM> is stuck and unable to move relative to the solenoid <NUM>. For example and without limitation, the magnitude of Icoil is greatest when a plunger stroke to pull the plunger <NUM> into the solenoid <NUM> is initiated. After a plunger stroke is initiated, Icoil decreases significantly due to the interaction between the magnetic flux created by the movement of the plunger <NUM> and the magnetic flux of the coil <NUM>. An increase in Icoil to initiate a plunger stroke that is not followed by a decrease in Icoil can be indicative of the plunger <NUM> being stuck and unable to move relative to the solenoid <NUM>.

Accordingly, at step <NUM> of the plunger diagnostic <NUM>, the processor <NUM> checks the current signature of the coil <NUM> from the time interval when the accessory <NUM> should have tripped the circuit breaker to determine whether an initial increase of Icoil (to initiate a plunger stroke) was followed by a significant decrease (indicative of the plunger <NUM> moving into the solenoid <NUM>). If the processor <NUM> determines at step <NUM> that the current signature of the coil <NUM> does not indicate movement of the plunger <NUM>, then the processor <NUM> triggers an alarm at step <NUM> notifying the user to check whether the plunger <NUM> is stuck. If, however, the processor <NUM> determines at step <NUM> that the current signature of the coil <NUM> indicates that there was movement of the plunger <NUM> at the time interval of the necessary trip, then the processor <NUM> triggers an alarm at step <NUM> notifying the user to check the circuit breaker because a necessary trip did not occur and the accessory <NUM> is functioning properly. The plunger diagnostic then concludes at step <NUM>.

Including self-diagnostic functionality in the accessory <NUM> with regard to the internal components of the accessory <NUM> enables the accessory <NUM> to immediately alert a user of the associated circuit breaker if any of the internal components of the accessory <NUM> are failing or no longer operational. This functionality presents several advantages. First, it alerts the user that there is an issue with the accessory <NUM>, as opposed to the circuit breaker, or vice versa, in the event that a necessary trip fails to occur. Second, it alerts the user as to which particular internal actuating component of the accessory <NUM> is failing. Third, the continuous evaluation of the sufficiency of the accessory <NUM> internal components alerts the user of any operating issues in a timely manner, so that the failing or nonoperational component can be replaced before the accessory <NUM> fails to operate as needed or in enough time to minimize the damage from a failure of the accessory <NUM>.

Claim 1:
An accessory device (<NUM>) structured to be operatively connected to an operating mechanism of a circuit breaker, the operating mechanism being operatively connected to separable contacts of the circuit breaker, the accessory device (<NUM>) comprising:
a power section (<NUM>) structured to be electrically connected to a power source (<NUM>), the power section (<NUM>) comprising:
an actuator (<NUM>) structured to actuate the operating mechanism of the circuit breaker, the actuator (<NUM>) comprising:
a solenoid (<NUM>) comprising a conductive coil (<NUM>); and
a ferromagnetic plunger (<NUM>) coupled to the solenoid (<NUM>) and structured to move relative to the solenoid (<NUM>) in response to current flowing through the solenoid;
a current sensor (<NUM>) structured to sense a current flowing through the power section (<NUM>); and
a control section (<NUM>) electrically and operatively connected to the power section (<NUM>), the control section (<NUM>) comprising a processor (<NUM>),
characterized in that:
the processor (<NUM>) is configured to communicate with a trip unit (<NUM>) of the circuit breaker;
the processor (<NUM>) is configured to continually execute a coil diagnostic to determine an operating condition of the coil (<NUM>) whenever the accessory device (<NUM>) is receiving power from the power source (<NUM>),
the processor (<NUM>) is configured to determine the operating condition of the coil (<NUM>) based on a measurement of current Icoil flowing through the coil (<NUM>),
upon receiving information from the trip unit (<NUM>) indicating that the separable contacts failed to trip open under conditions in which the accessory device (<NUM>) should have tripped the separable contacts open, the processor (<NUM>) is configured to:
check a most recent measurement of the current Icoil to determine if the coil (<NUM>) is operating normally, and issue an alarm to a user if the most recent measurement of the current Icoil indicates that the coil (<NUM>) is not operating normally,
determine an operating condition of the plunger (<NUM>) based on a current signature of the coil (<NUM>) if the coil diagnostic indicates that the coil (<NUM>) is operating normally, and issue an alarm to the user if the current signature of the coil (<NUM>) indicates that the plunger (<NUM>) is not operating normally, and
issue an alarm to the user indicating that the circuit breaker should be checked if the current signature indicates that the plunger (<NUM>) is operating normally.