Patent ID: 12237661

DESCRIPTION OF THE PREFERRED EMBODIMENTS

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 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.

FIG.1is a diagram of a solid state circuit breaker10in accordance with an example embodiment of disclosed concept. The solid state circuit breaker10may be part of a larger system including additional circuit breakers, solid state and/or mechanical circuit breakers, such as the system shown inFIG.2.

The solid state circuit breaker10is structured to be electrically connected between a power source and a load12via LINE and LOAD conductors2,4. An upstream circuit breaker may be disposed between the power source and the solid state circuit breaker10. The solid state circuit breaker10is structured to trip open or switch open to interrupt current flowing to the load12in the case of a fault condition (e.g., without limitation, an overcurrent condition) to protect the load12, circuitry associated with the load12, as well as the components within the solid state circuit breaker10.

The solid state circuit breaker10includes a solid state switch100, an electronic trip unit200, an operating mechanism300, a sensor400, and mechanical contacts500. The solid state switch100includes solid state switching elements (e.g., without limitation, metal-oxide-semiconductor-field-effect-transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs)) that are structured to turn-on and turn-off (i.e., open and close) to allow or interrupt current flowing to the load12. The solid state switch100is electrically coupled to the load12and the electronic trip unit200.

The electronic trip unit200is structured to control the solid state switch100to open and close and also controls the operating mechanism300to trip open the mechanical contacts500based on a signal from the sensor400. The electronic trip unit200may include a processing unit that may include a processor and a memory. The processor may be, for example and without limitation, a microprocessor, a microcontroller, or some other suitable processing device or circuitry. The memory can be any of one or more of a variety of types of internal and/or external storage media such as, without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the like that provide a storage register, i.e., a machine readable medium, for data storage such as in the fashion of an internal storage area of a computer, and can be volatile memory or nonvolatile memory. The memory may store a firmware solution for solid state interlocking (SSI) where a first solid state circuit breaker, e.g., a downstream circuit breaker, fails to open its solid state switch, e.g., due to a short circuit of a solid state switch therein. The SSI is performed by the first solid state circuit breaker and a second circuit breaker, e.g., an upstream circuit breaker to the first solid state circuit breaker. The second circuit breaker may or may not be a solid state circuit breaker. An SSI-enabled downstream circuit and SSI-enabled upstream circuit breaker may together monitor and respond to interruption capability of their power semiconductors. The SSI is discussed further with reference toFIG.2.

The electronic trip unit200is structured to determine a fault condition (e.g., without limitation, an overcurrent fault) and control the solid state switch100to open in response to the fault condition. Opening the solid state switch100interrupts current flowing to the load12.

The operating mechanism300is structured to open the mechanical contacts500in response to a signal from the electronic trip unit200. Opening the mechanical contacts500provides galvanic isolation between the power source and the load12. For example and without limitation, the operating mechanism300is structured to cause mechanical contacts500to open by, for example and without limitation, moving a movable arm to cause the mechanical contacts500to separate. The electronic trip unit200is structured to control the operating mechanism300to open the mechanical contacts500only after the solid state switch100has been opened to interrupt current flowing through the solid state circuit breaker10. In some example embodiments, the mechanical contacts500are not designed to interrupt a rated current flowing through the solid state circuit breaker10, and the solid state circuit breaker10may lack components, such as an arc chute, to deal with the effects of the mechanical contacts500interrupting a rated current. As such, the mechanical contacts500should only be opened when the current flowing through the solid state circuit breaker10has dropped to a level where it is safe to open the mechanical contacts500.

The sensor400may be a current sensor (e.g., without limitation, a current transformer, a Hall-Effect sensor, etc.) structured to sense the current flowing through the solid state circuit breaker10. The output of the sensor400may be provided to the electronic trip unit200.

The electronic trip unit200is structured to detect a failure mode of the solid state circuit breaker10. The failure mode is a failure of the solid state switch100to open. In response to detecting the failure mode, the electronic trip unit200is structured to output a request to an upstream circuit breaker. In response to the request, the upstream circuit breaker is structured to interrupt current flowing to the solid state circuit breaker10, which results in the current flowing through the solid state circuit breaker10dropping. The electronic trip unit200is structured to monitor the current flowing through the solid state circuit breaker10while it is dropping and to determine when the current drops to a predetermined level. The predetermined level is a level where it is safe to open the mechanical contacts500. An example predetermined level is5A. However, the predetermined level may be modified without departing from the scope of the disclosed concept. Once the current reaches the predetermined level, the electronic trip unit200controls the operating mechanism300to open the mechanical contacts500. After opening the mechanical contacts500, the electronic trip unit200sends a clear request to the upstream circuit breaker. The clear request indicates that the upstream circuit breaker can stop interruption of current flowing to the solid state circuit breaker10. The drop in current flowing through the solid state circuit breaker10allows safe opening of the mechanical contacts500. The clear request allows the upstream circuit breaker to quickly restore current so that interruption to other loads downstream of the upstream circuit breaker is minimized. In some example embodiments, the duration of the interruption may be on the order of microseconds and will have little effect on the other loads downstream of the upstream circuit breaker.

FIG.2is a diagram of a system1in accordance with an example embodiment of the disclosed concept. The system1may include one or more solid state circuit breakers10. InFIG.2, the system1includes a plurality of circuit breakers, e.g., an upstream circuit breaker10A and downstream solid state circuit breakers10B-N, where N is an integer. The upstream circuit breaker10A may or may not be a solid state circuit breaker.

The circuit breakers10A-N are electrically coupled to one another, and communicate with one another via any suitable communications protocols. For example, the circuit breakers10A-N may be structured to communicate through wired or wireless communication. In wired communication, the circuit breakers10A-N may communicate via powerline communication or via control lines. It will be appreciated that any suitable manner of communication may be employed between the circuit breakers10A-N without departing from the scope of the disclosed concept. The circuit breakers10A-N may communicate with one another to, e.g., request or perform a solid state interlocking (SSI) when a failure mode, e.g., a failure to open a solid state switch, is detected and one or more of the solid state circuit breakers fail to open. For example, if a solid state switch100of a downstream solid state circuit breaker10B is short-circuited100A, the solid state switch100of the downstream solid state circuit breaker10B may not open. When the solid state switch100is unable to open and current continues flowing through the downstream solid state circuit breaker10B, it is unsafe to open the mechanical contacts500A. In response to the failure mode, the downstream circuit breaker10B transmits a request (e.g., an SSI request) to the upstream circuit breaker10A.

The SSI is both a hardware and firmware solution to one of the failure modes associated with the power semiconductor devices in a solid state circuit breaker. The SSI offers a firmware solution in that it provides a communication scheme and allows an upstream circuit breaker to recognize and react to a downstream circuit breaker with a failure mode, e.g., when the solid state circuit breaker is unable to open during a short-circuit event. For example, when an SSI enabled solid-state circuit breaker senses a short circuit failure in one or more of its semiconductor devices, it sends an SSI request to the closest upstream circuit breaker, and responsively, the closest upstream circuit breaker interrupts current flowing to the downstream circuit breaker. The SSI request may indicate that there was a failure to open the solid state switch of the downstream circuit breaker10B and request the upstream circuit breaker10A to interrupter current flowing to the downstream circuit breaker10B. The SSI may be performed via an interruption logic embedded in the circuit breakers.

The downstream circuit breaker10B is structured to monitor the current dropping due to interruption and then open its mechanical contacts500A when the current reaches a predetermined level. The predetermined level may be a current level in which the requesting circuit breaker's mechanical contacts can safely open in all phases. The upstream circuit breaker10A may create the interrupt current flowing to the downstream circuit breaker10B by temporarily turning off its semiconductor device, e.g., an SiC MOSFET, IGBT, etc. The duration of the current interruption by the upstream circuit breaker may be tuned for a minimal impact on other loads downstream of the upstream circuit breaker10A. The duration of the current zero may be microseconds (μs). In examples in which the upstream circuit breaker is a non-solid state circuit breaker (non-SSCB), the non-SSCB upstream circuit breaker may interrupt current by opening its mechanical contacts. As such, the non-SSCB may also require an additional action to reclose itself. In some example embodiments, though, the non-SSCB may be able to reclose its mechanical contacts.

Once the current is interrupted, the downstream solid state circuit breaker10B detects the drop in current flowing through it reaching the predetermined level via a current sensor (e.g., the current sensor400described with reference toFIG.1) and opens its mechanical contacts500A. Upon opening the mechanical contacts500A, the downstream circuit breaker10B may send a clear request to the upstream circuit breaker10A. The clear request may indicate that the failure mode is now remedied, e.g., the mechanical contacts of the downstream circuit breaker10B are now open, and thus, it is clear for the upstream circuit breaker10A to terminate the SSI mechanism and resume its normal operations.

Upon receiving the clear request, the upstream circuit breaker10A may terminate the SSI, e.g., by closing its mechanical contacts or solid state switch. The upstream circuit breaker10A then resumes its normal operations.

FIG.3includes waveforms for the current flowing through downstream and upstream circuit breakers in accordance with an example embodiment of disclosed concept. A is a waveform for the current flowing through a downstream circuit breaker, e.g., an SSI enabled downstream solid state circuit breaker. B is a waveform for the current flowing through an upstream circuit breaker, e.g., an SSI-enabled upstream circuit breaker.

At time t1, both the downstream circuit breaker and the upstream circuit breaker are closed.

Subsequent to time t1and prior to time t2, a failure mode (i.e., a failure to open the solid state switch) of the downstream circuit breaker, occurs. The downstream circuit breaker detects this failure mode.

At time t2, the downstream circuit breaker transmits a request to the upstream circuit breaker. In response to the request, the upstream circuit breaker interrupts current flowing to the downstream circuit breaker, causing the current flowing through the downstream circuit breaker to drop. The downstream circuit breaker then waits for the current flowing through it to drop to a predetermined level where it is safe to open its mechanical contacts.

At time t3, the current flowing through the downstream circuit breaker reaches the predetermined level. In one example, the predetermined level may be5A or less for a100A solid state circuit breaker. However, it will be appreciated that other predetermined levels may be used without departing from the scope of the disclosed concept. At time t3, the downstream may begin the process of opening its mechanical contacts. Since this process takes an amount of time, the mechanical contacts may not actually be opened until t4. Once the mechanical contacts are open, the downstream circuit breaker sends a clear request to the upstream circuit breaker, indicating that the upstream circuit breaker can stop interruption of current flowing to the downstream circuit breaker.

At time t5, the upstream circuit breaker may receive the clear request from the downstream circuit breaker and stop interruption of current to the downstream circuit breaker by, for example, closing its solids state switch or mechanical contacts.

Between time t5, when the upstream circuit breaker stops interruption of current, and time t6, the current flowing through the upstream circuit breaker rises to its normal level, which it reaches at time t6.

FIG.4is a flow chart for a method400in accordance with an example embodiment of the disclosed concepts. The method may be performed by an upstream circuit breaker and a downstream circuit breaker of the circuit interrupter and respective processing units as described with reference toFIGS.1-3.

At410, the first circuit breaker detects a failure mode (i.e., a failure to open the solid state switch) The first circuit breaker may be a downstream circuit breaker as described with reference toFIG.2.

A request may indicate that there was a failure to open the solid state switch of the first circuit breaker and request the second circuit breaker to interrupt current flowing to the first circuit breaker. At420, the first circuit breaker transmits the request to a second circuit breaker. The second circuit breaker may be an upstream circuit breaker as described with reference toFIG.2. There may be one or more upstream circuit breakers within the circuit interrupter, and the downstream circuit breaker transmits the SSI request signal to the closest upstream circuit breaker. The upstream circuit breaker may be either a solid state circuit breaker or non-solid state circuit breaker.

At430, the second circuit breaker receives the request from the first circuit breaker.

At440, the second circuit breaker interrupts current flowing to the first circuit breaker The second circuit breaker may interrupt the current by temporarily turning off its semiconductor device, e.g., an SiC MOSFET, IGBT, etc., via an interruption logic embedded within the memory of the upstream circuit breaker. The duration of the interruption by the second circuit breaker may be tuned for a minimal impact on the downstream breaker's loads. The duration be microseconds (μs).

At450, the first circuit breaker opens the mechanical contacts when the current flowing through it drops to a predetermined level. The second circuit breaker waits for a clear request signal from the first circuit breaker. The clear request signal may indicate that the mechanical contacts of the first circuit breaker have been opened, and thus, it is clear for the second circuit breaker to stop interruption and resume its normal operations.

At460, the first circuit breaker transmits the clear request to the second circuit breaker.

At470, the second circuit breaker stops interruption of current to the first circuit breaker based at least in part on the clear request received. The second circuit then resumes normal operation.

FIG.5is another flow chart for a method500in accordance with an example embodiment of the disclosed concepts. The method may be performed by an upstream circuit breaker and a downstream circuit breaker of the circuit interrupter and respective processing units coupled to respective memories therein as described with reference toFIGS.1-3.

At510, both the downstream circuit breaker and the upstream circuit breaker are closed and perform normal operations.

At512, a fault event within the downstream circuit breaker occurs. The fault event may include an overcurrent event.

At514, the downstream circuit breaker detects that a failure mode occurred. That is, the downstream circuit breaker detects that its solid state switch has failed to open.

At516, the downstream circuit breaker transmits a request signal to the upstream circuit breaker

At518, the upstream circuit breaker receives the request from the downstream circuit breaker.

At520, the upstream circuit breaker opens its solid state switch to interrupt current flowing to the downstream circuit breaker.

At522, the downstream circuit breaker detects the level of current flowing through it and when it detects that the level of current has dropped to a predetermined level, the method proceeds to526. The downstream circuit breaker may detect the current zero via a current sensor (e.g., a current sensor400discussed with reference toFIG.1). The predetermined level is a level at which it is safe for the downstream circuit breaker to open its mechanical contacts

At524, the downstream circuit breaker opens its mechanical contacts.

At526, the downstream circuit breaker transmits the clear request to the upstream circuit breaker.

At528, the upstream circuit breaker receives the clear request from the downstream circuit breaker.

At530, the upstream circuit breaker stops interrupting current flowing to the downstream circuit breaker by, for example, opening its solid state switch.

At532, the upstream circuit breaker resumes normal operations.

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.