Patent Application
20100066470
Embodiments of the invention disclosed herein relate to circuit interrupters or circuit breakers. More specifically, embodiments of the invention relate to lowering the force required of sensors, such as fault detectors, in trip apparatus for circuit interrupters or circuit breakers.
Circuit interrupters or circuit breakers use various trip devices to detect a fault and open a circuit to which they are connected. The trip devices include sensors and activate an operating mechanism of the breaker that moves a movable contact out of engagement with a fixed contact when the fault is detected. Some circuit breakers are also configured to trip other circuit breakers remotely.
One type of trip device used in circuit breakers is an electromagnetic trip device, which is generally used to open the breaker during a surge event. An example of an electromagnetic trip device is a solenoid serially connected to a line conductor of the breaker and arranged to activate the operating mechanism when current in the line conductor exceeds a predetermined level.
Another type of trip device used in circuit breakers is a thermal trip device, which is generally used to open the breaker during an overload event. An example of a thermal trip device is a thermal element, typically a bimetallic element (bimetal), serially connected to a line conductor of the breaker and arranged to activate the operating mechanism when current in the line conductor has exceeded a predetermined level for a predetermined amount of time. This type of bimetal trip device is known in the art as a directly-heated bimetal. Other bimetal trip devices may be thermally connected to a line conductor through a heating element that itself is serially connected to the line conductor. This type of bimetal/heater trip device is known in the art as an indirectly-heated bimetal.
Many circuit breakers employ both electromagnetic and thermal trip devices in a so-called thermal-magnetic trip unit. In a thermal-magnetic trip unit, the electromagnet or the thermal element or both may be required to provide or overcome a relatively high trip force. The amount of force required to trip the mechanism of some breakers can be as much as 4 Newtons (N), and larger breakers can have much higher trip forces. Additionally, some arrangements have a trip bar, which is what the trip device is arranged to move, directly attached to the mechanism. This couples the mechanism and trip device(s).
Some designs use a secondary latching system, such as is used in many interchangeable trip unit designs, which can reduce the force required by the trip device(s) to trip the mechanism. In an interchangeable trip unit configuration, the trip device contacts a trip bar that is part of a secondary latching system containing stored energy in the form of springs. The electromagnetic or thermal trip device, or both, can then release this secondary latching system, which then trips the mechanism. This configuration reduces coupling between the trip device and the mechanism, but does not eliminate the coupling and adds a significant amount of complication to the design. The second latching system also adds cost. Additionally, though the force required to release the latching system is reduced, the required force is still somewhat large. For example, in a breaker requiring about 4 N to trip the mechanism, the second latching system can still require a relatively large force of about 2.5 N.
There is thus a need for a trip apparatus that decouples the apparatus from the operating mechanism and reduces the amount of force required from the fault detector(s) to trip the mechanism.
Many circuit breakers also use auxiliary trip systems. Auxiliary trip systems can be used in several ways, but are typically used to trip a breaker more rapidly than a primary trip device of the breaker. For example, a typical primary electromagnetic trip device can have an intentional delay, such as one cycle, to give a downstream breaker an opportunity to trip and eliminate a fault danger to the upstream breaker. This intentional delay may be disadvantageous in higher current surge events, and thus an auxiliary trip device can be employed to trip the breaker more rapidly under such circumstances.
Prior art auxiliary trip systems include, for example, pressure powered auxiliary trip systems and magnetic trip systems. Several design constraints make auxiliary trip systems particularly difficult to design. Most auxiliary trip systems must harvest residual energy in the breaker to create mechanical energy to trip the breaker. For example, in pressure powered auxiliary trip systems, breaker exhaust gas pressure is used as an energy source, and in magnetic trip auxiliary systems, magnetic force generated by current flow is used. In both example types, the auxiliary trip system must harvest enough energy to trip the mechanism and convert the residual energy to a relatively high amount of mechanical force, which may be difficult to accomplish, particularly for pressure powered auxiliary trip systems.
There is thus a need for an auxiliary trip system that requires less energy for operation and that is easier to tune.
A circuit interrupter trip apparatus operably connected to an operating mechanism of a circuit interrupter includes a sensor, such as a fault detector, and a switch operably connected and responsive to the sensor. The sensor is configured to change the operating state of the switch in response to detection of a predetermined condition, such as an electrical fault. A controller is operably connected to the switch and is configured to activate the operating mechanism in response to a change in the operating state of the switch.
In addition, a circuit interrupter including a first electrical contact and a second electrical contact disposed in separable communication with the first electrical contact has an operating mechanism disposed and configured to selectively open and close the first and second electrical contacts. A first trip device is operably connected to the operating mechanism to activate the operating mechanism in response to at least one first condition being met, and a second trip device is operably connected to the operating mechanism to activate the operating mechanism in response to at least one second condition being met. The second trip device includes a controller configured to issue a trip command, a switch having at least two operating states, the switch being in electrical communication with the controller, and a sensor disposed and configured to change the operating state of the switch in response to detecting a predetermined electrical condition, the predetermined electrical condition being an at least one second condition. An actuator operably connected to the controller and the operating mechanism is disposed and configured to activate the operating mechanism in response to the trip command from the controller. The controller is configured to issue the trip command to the actuator in response to the change in the operating state of the switch.
A circuit interrupter trip method includes providing a sensor, providing a switch, and providing a controller. The method also includes connecting the switch to controller, configuring the sensor such that when a predetermined condition is detected it changes an operating state of the switch. In embodiments, the method continues by monitoring the operating state of the switch with the controller and activating an operating mechanism of a circuit interrupter with the controller when the operating state of the switch changes.
With reference to the accompanying Figures, examples of a trip apparatus according to embodiments of the invention are disclosed as a unit unto itself, as part of a typical thermal-magnetic circuit breaker, and as an auxiliary trip apparatus. For purposes of explanation, numerous specific details are shown in the drawings and set forth in the detailed description that follows in order to provide a thorough understanding of embodiments of the invention. It will be apparent, however, that embodiments of the invention may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.
As seen in
While embodiments of the invention are herein disclosed having a movable and a fixed contact, a solenoid as an example electromagnetic trip device, and a bimetal as a thermal trip device, it will be appreciated that the scope of the invention is not so limited. For example, embodiments of the invention may also employ a pair of contacts where both are movable, or may employ more than one pair of contacts, such as in a double-break system. Other embodiments may employ non-solenoid electromagnetic trip devices such as a magnet/armature arrangement, and may employ other thermal elements such as shape memory devices for the thermal trip device, for example. All such alternative embodiments are contemplated and considered within the scope of the invention disclosed herein.
As seen in
The switch 220 is in electrical communication with a controller 230 that is also in electrical communication with an actuator 240. The controller 230 monitors the operating state of the switch 220 and/or responds to a change in the operating state of the switch 220 and activates the actuator 240 when appropriate. In an embodiment, a power source 250 is included to provide power to the controller 230, the actuator 240, and/or the switch 220. The power source 250 can be a current transformer (CT), battery, or other suitable power source.
The controller 230 of an embodiment is a printed circuit board (PCB) or board computer in electrical communication with the switch 220 and the actuator 240 and configured to issue or send a trip signal to the actuator 240 in response to a change in the switch operating state. In alternative embodiments, the controller can include a microprocessor in electrical communication with the switch 220 and the actuator 240 and is equipped with logic that activates the actuator 240 in response to a change in the operating state of the switch that also performs other functions.
While the controller 230 has been described in the example embodiment as a board computer, it can be any suitable electronic device that can receive data and computer executable instructions, execute the instructions to process the data, and present results. The controller 230 can also be, but is not limited to, a microprocessor, microcomputer, a minicomputer, an optical computer, a board computer, a complex instruction set computer, an application specific integrated circuit, a reduced instruction set computer, an analog computer, a digital computer, a solid-state computer, a single-board computer, or a combination of any of these. Instructions can be delivered to the controller 230 via an electronic data card, voice activation, manual selection and control, electromagnetic radiation, and electronic or electrical transfer.
An embodiment of the invention can include computer-implemented processes and apparatus for practicing such processes, such as the controller 230. Additionally, an embodiment can include a computer program product including computer code, such as object code, source code, or executable code, on tangible media, such as magnetic media (floppy diskettes, hard disc drives, tape, etc.), optical media (compact discs, digital versatile/video discs, magneto-optical discs, etc.), random access memory (RAM), read only memory (ROM), flash ROM, erasable programmable read only memory (EPROM), or any other computer readable storage medium on which the computer program code is stored and with which the computer program code can be loaded into and executed by a computer. When the computer executes the computer program code, it becomes an apparatus for practicing the invention, and on a general purpose microprocessor, specific logic circuits are created by configuration of the microprocessor with computer code segments. A technical effect of the executable instructions is to activate an actuator when a fault is detected by a fault detector.
The computer program code is written in computer instructions executable by the controller, such as in the form of software encoded in any programming language. Examples of suitable programming languages include, but are not limited to, assembly language, VHDL (Verilog Hardware Description Language), Very High Speed IC Hardware Description Language (VHSIC HDL), FORTRAN (Formula Translation), C, C++, C#, Java, ALGOL (Algorithmic Language), BASIC (Beginner All-Purpose Symbolic Instruction Code), APL (A Programming Language), ActiveX, HTML (HyperText Markup Language), XML (eXtensible Markup Language), and any combination or derivative of one or more of these.
As seen in
As seen in the exemplary embodiment of
As seen in
In
By using switches, and especially microswitches, in trip apparatus to trigger an actuator to trip, embodiments significantly reduce the amount of force a sensor, such as a fault detector, must produce to trip a breaker. The sensor need only produce enough force to change the state of the switch, which results in the actuator tripping the breaker. The actuator provides the force previously required of the sensor to trip the breaker. Sensors in embodiments can thus be much smaller than those in prior art devices, which can result in cost reductions and size reductions, but can also produce a more easily calibrated trip apparatus.
While the instant disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope thereof. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiment(s) disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
