1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as remote control subminiature circuit breakers with embedded arc fault protection. The disclosed concept also relates to systems employing remote control subminiature circuit breakers with embedded arc fault protection.
2. Background Information
Electrical switching apparatus include, for example, circuit switching devices; circuit interrupters, such as circuit breakers; network protectors; contactors; motor starters; motor controllers; and other load controllers.
One use of miniature or subminiature circuit breakers, for example, is in devices or environments with limited space and/or weight limitations, such as, for example and without limitation, aircraft electrical systems, where they not only provide overcurrent protection, but also serve as switches for turning equipment on and off. As such, they are subjected to heavy use and, therefore, must be capable of performing reliably over many operating cycles.
Subminiature circuit breakers have the typical circuit breaker components, such as a non-conductive housing, an external actuator, at least two external terminals structured to be coupled to a line and a load, a pair of separable contacts including a first, stationary contact electrically coupled to one external terminal and a second, movable contact couple to the other external terminal, an operating mechanism structured to move the separable contacts between a first, closed position wherein the contacts engage and electrically connect each other, and a second position wherein the contacts are separated, and a trip device structured to latch the operating mechanism in the first position until an over-current condition occurs. The operating mechanism includes a bias element (e.g., without limitation, spring) biasing the separable contacts toward the second position. Thus, when the trip device is actuated, the latch releases the operating mechanism and the separable contacts move to the second position. The operating mechanism is also coupled to the external actuator. The external actuator is structured to move the separable contacts to the first position after a trip event, or may be used to manually separate the contacts.
Known circuit breakers having arc fault protection include a trip device with at least two tripping mechanisms; one mechanism for an over-current situation and one mechanism for an arc fault on the load side of the circuit breaker. The over-current mechanism typically includes an elongated bimetal element that bends in response to temperature changes. The act of bending actuates the latch, thereby allowing the operating mechanism to separate the separable contacts. Heat is created in response to current passing through the bimetal element. Thus, the greater the amount of current, the greater the degree of bending. The electronic arc fault mechanism of such breakers includes an electronic arc fault detector and a solenoid assembly. When the electronic arc fault detector sensed an arc, a the solenoid sends a pulse and actuates the trip device. Among other disadvantages, such designs were relatively large occupying a significant amount of space.
Additionally, under certain circumstances, it would be may be desirable to provide remote control operation of subminiature circuit breakers.
There is, therefore, room for improvement in electrical switching apparatus, such as subminiature circuit breakers, and in systems employing the same.
These needs and others are met by embodiments of the disclosed concept, which are directed to a remote control electrical switching apparatus, such as a subminiature circuit breaker, having embedded arc fault protection, and to systems employing the same.
As one aspect of the disclosed concept, an electrical switching apparatus comprises: a housing assembly; separable contacts enclosed by the housing assembly; an operating mechanism for opening and closing the separable contacts, the operating mechanism includes an actuator device and a latching assembly; a first trip device structured to trip open the separable contacts in response to an overcurrent condition; a second trip device structured to trip open the separable contacts in response to an arc fault, a ground fault or a remotely transmitted signal; a first solenoid operatively coupled to the actuator device; and a second solenoid operatively coupled to the latching assembly.
The separable contacts may include a fixed contact and a movable contact, wherein the separable contacts are movable between a first position corresponding to the movable contact and the fixed contact being electrically connected, and a second position corresponding to the movable contact and the fixed contact being spaced apart and not electrically connected. The operating mechanism may further include a biasing element, wherein the biasing element biases the separable contacts toward the second position. The latching assembly may include a catch lever and a mechanical linkage, the biasing element may be a spring, and the actuator device may be a reset button, wherein the reset button is structured to compress the spring and reset the catch lever of the latching assembly.
The first trip device may include a bi-metallic element, wherein the mechanical linkage cooperates with the catch lever and the bi-metallic element and wherein, in response to the overcurrent condition, the bi-metallic element heats up causing the bi-metallic element to bend, thereby moving the mechanical linkage and the catch lever to release the spring and trip open the separable contacts. The first solenoid may be a reset solenoid, wherein the reset solenoid includes a coil, and wherein the coil is operable to electrically reset the separable contacts. The second solenoid may be a trip solenoid, wherein the trip solenoid includes a coil, and wherein the coil of the trip solenoid is operable to move the catch lever, thereby electrically tripping open the separable contacts.
In accordance with another aspect of the disclosed concept a system comprises: a mechanism control module; an arc fault detection module; a communications interface; a power supply; a controller; and an electrical switching apparatus comprising: a housing assembly; separable contacts enclosed by the housing assembly; an operating mechanism for opening and closing the separable contacts, the operating mechanism including an actuator device and a latching assembly; a first trip device structured to trip open the separable contacts in response to an overcurrent condition; a second trip device structured to trip open the separable contacts in response to an arc fault, a ground fault or a remotely transmitted signal; a first solenoid operatively coupled to the actuator device; and a second solenoid operatively coupled to the latching assembly.
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:
The disclosed concept is described in association with remote control subminiature aircraft circuit breakers, although the disclosed concept is applicable to a wide range of electrical switching apparatus.
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 employed herein, the term “fastener” refers to any suitable connecting or tightening mechanism expressly including, but not limited to, screws, bolts and the combinations of bolts and nuts (e.g., without limitation, lock nuts) and bolts, washers and nuts.
As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts.
As employed herein, the term “number” shall mean one or an integer greater than one (i.e., a plurality).
The circuit breaker 2 includes a housing assembly 4, made from a non-conductive material such as, for example and without limitation, plastic, a pair of separable contacts 6, an operating mechanism 8, and a number of trip devices 10,12. An actuator device (e.g., without limitation, reset button 14) is movably coupled to the housing assembly and structured to travel in the vertical direction to actuate (e.g., reset) the separable contacts. The separable contacts 6 include a first, fixed contact 16, and a second, movable contact 18. Both the first and second contact 16,18 each are coupled to, or are integral with, a corresponding terminal 20,22, respectively, that extends outside said housing 4. The external terminals 20,22 are structured to be coupled to either a line or a load.
The operating mechanism 8 is coupled to, and structured to move, the separable contacts 6 between a first, closed position (
The thermo-mechanical mechanism 30 includes a bi-metallic element 32. Load circuit current is passed through a bi-metallic element 32 causing it to heat up proportional to I2t, which correlates to the power dissipated in the power distribution wires. The bi-metallic element 32 is designed such that its bending displacement is closely proportional to its temperature, and is mechanically coupled to a spring-loaded latching assembly 40 in the circuit breaker 2. The latching assembly 40 includes a catch lever 42, which is structured to hold the separable contacts 6 closed. In operation, at a predetermined temperature, the bi-metallic element 32 displaces the catch lever 42 via a mechanical linkage 44 (shown in simplified form as a broken line, in
The subminiature circuit breaker 2 can be reset by moving the reset button 14, which is coupled to the separable contacts 6. That is, depressing the reset button 14 (e.g., without limitation, downward in the direction of arrow 80, from the perspective of
In the non-limiting example shown in
The first solenoid 50 is energized via the MCM 200, and is structured to electrically reset the circuit breaker 2 (i.e., contact closure). The second solenoid 60 is mechanically coupled to the latching assembly 40 in a similar manner as the bi-metallic element 32, previously discussed hereinabove. The second solenoid 60 is also controlled by the MCM 200, and functions to trip the latching assembly 40 when circuit current interruption is desired. Such interruption may, for example and without limitation, be in response to the detection of an arcing fault, a ground fault, or it may be in response to a remotely transmitted signal for control of electrical power to the load.
A current sensor 70 is employed to directly monitor the load circuit current, as shown in
As previously discussed, the primary purpose of the MCM 200 is to coordinate energizing of the first and second solenoids 50,60 to trip (i.e. open) or reset (i.e. close) the circuit breaker 2. In performing this coordination, the MCM 200 may retain knowledge on the closed versus open state of the circuit breaker 2 based on memory of previous commanded operations. Since manual reset using the reset button 14 is possible, independent of control from the MCM 200, memory alone may not be sufficient to know breaker contact state. It will, therefore, be appreciated that additional diagnostics may be used employing additional sensors (not shown). For example and without limitation, voltage sensors (not shown) may be used in conjunction with the current sensor 70 by the MCM 200 to determine the state of the circuit breaker separable contacts 6, thereby providing additional information for logical control of the solenoids 50,60. By way of example, without limitation, if such sensors identify the presence of voltage on the line and load terminals 20,22, this would indicate that the separable contacts 6 are closed and the latching assembly 40 is in the latched position. Similarly, if unequal voltages are detected on the terminals 20,22, the separable contacts 6 are in the open state. Non-zero current flow through the load terminal 22 of the circuit breaker 2 may also be used as an indication that the circuit breaker 2 is closed. It will be appreciated that further diagnostics of breaker status may also be employed. For example and without limitation, the MCM 200 could utilize a pair of auxiliary contacts (not shown) mechanically linked to the main circuit breaker contacts 6, as a method to determine the state of the circuit breaker 2.
The solenoids 50,60 are energized by a power supply 400 (shown in simplified form in
A Communications Interface (CI) circuit 500 (shown in simplified form in
In addition to communicating the status of the circuit breaker 2, the CI 500 also receives open and close commands from the controller 600 and passes them on to the MCM 200 to facilitate remote operation. The CI 500 may be comprised of electronic circuitry such as, for example and without limitation, analog devices, discrete logic, programmable logic devices (PLD), field-programmable gate arrays (FPGA), or microprocessor-based circuitry.
By monitoring the breaker open/close status from the MCM 200 in combination with fault indications from the AFDM 300, the cause of a breaker trip can be deduced either in the internal processor, or external to the breaker in the PDU or master controller 600. For example and without limitation, if the MCM 200 detects a breaker trip that is non-coincident with an arc or ground fault having been detected by the AFDM 300 or Ground Fault Detection Module (GFDM)(not shown) or an open command from the controller 600, the trip must be the result of the thermal trip mechanism (e.g., thermo-mechanical mechanism 30) responding to an overcurrent fault. This condition status can be transmitted to the controller 600 via the CI 500.
The power supply 400 is employed to power the MCM 200, AFDM 300, and CI 500 electronic circuitry. By way of example, without limitation, the power may be derived off the input line voltage with respect to vehicle chassis ground (not shown), parasitically off the current flowing through the circuit breaker 2, or from an energy storage element (e.g., without limitation, batteries (not shown); capacitors (not shown)). The power supply 400 also provides voltage transient protection to the electronics in case of source power surges (e.g., without limitation, lightning strikes).
It will be appreciated that it is within the scope of the disclosed concept to integrate the functions of the MCM 200, AFDM 300, and CI 500 into a single electronics assembly with shared central processing elements (e.g., without limitation, microcontroller). Among other benefits, with would serve to leverage advantages in cost, size, and weight.
As best shown in
In the non-limiting example of
It will, therefore, be appreciated that the threaded portion 130 (partially shown in hidden line drawing in
Accordingly, it will be appreciated that the disclosed remote controlled subminiature circuit breaker 2 provides size, weight and manufacturing cost improvements over known remote control circuit breaker designs. Among other benefits, the circuit breaker 2 can trip/open upon thermal overload and be reset manually, can be remotely opened or closed without the presence of a thermal or AFCI fault, can detect and trip/open if a thermal or arcing even is sensed, can be manually reset or remotely (i.e., electrically) reset, and can indicate if the fault was thermal or an arcing event.
While specific embodiments of the disclosed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.
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European Patent Office, “Internationai Search Report and Written Opinion” for International Application No. PCT/US2013/029479, Jun. 12, 2013. |
Number | Date | Country | |
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20130242450 A1 | Sep 2013 | US |