Solid state circuit breaker with self-diagnostic, self-maintenance and self-protection functions

Abstract

To provide a solid-state circuit breaker (SSCB) having self-diagnosis, self-maintenance and self-protection functions.SOLUTION: The SSCB100 includes a power semiconductor device 106, an air-gap disconnect unit 108 connected in series with the power semiconductor device, a sensing and driving circuit 104 that switches off the power semiconductor device upon detecting a short-circuit or a long-duration over-load, and a microcontroller unit (MCU) 102 that triggers the air-gap disconnect unit to form an air-gap and isolate the attached load after switching off the power semiconductor device. The MCU monitors the operation of the air gap disconnecting unit, the power semiconductor devices and other critical components of the SSCB and, if applicable, takes corrective measures to prevent damage, destruction of the SSCB and connected loads and to protect people and the environment from being exposed to dangerous electrical conditions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 895,182, filed September 3, 2019. [Background technology]

[0002] Circuit breakers are used in electrical power distribution systems to protect electrical circuits and their loads from short circuits and overloads. Conventional circuit breakers typically have an electromechanical structure that includes an electromagnet that operates to separate the breaker contacts as quickly as possible when a short circuit occurs, and a thermally responsive bimetallic strip that separates the circuit breaker contacts after an overload persists in the circuit for an unacceptably long duration.

[0003] While conventional circuit breakers are effective at isolating faults once they trip, one significant drawback is their slowness, typically requiring several milliseconds to respond to a fault and disconnect it. To circumvent this limitation, efforts have been made in recent years to adapt high-power semiconductors (e.g., "solid-state" devices) for circuit breaker applications. Solid-state devices are attractive because they can be controlled to disconnect a fault in just a few microseconds, compared to the several milliseconds it typically takes a conventional circuit breaker to disconnect a similar fault. Fast response times are advantageous because they reduce the risk of fire, damage to electrical equipment, and the possibility of arc flashes. Furthermore, because the operating characteristics of solid-state devices vary little from part to part, circuit breakers can be constructed from solid-state devices that exhibit precise and well-controlled time-current characteristics. This differs from conventional circuit breakers, which exhibit large variations in time-current characteristics due to thermal, magnetic, and mechanical construction.

[0004] Given their various advantages, solid-state circuit breakers have the potential to replace conventional circuit breakers in the not-too-distant future. However, for that transition to occur, solid-state circuit breakers must be designed to be durable and capable of operating unattended, i.e., for extended periods of time, without the need for excessive human monitoring and maintenance. Consistent with that objective, a solid-state circuit breaker should have the ability to monitor its own critical functions, identify any deviations from its intended operation, diagnose and predict the cause and source of faults, protect itself from hazardous conditions that could otherwise lead to its damage and / or harm to people and the environment, and, when conditions permit, shut itself off to electrically and galvanically isolate its associated loads. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Application No. 16 / 898,538 [Patent Document 2] U.S. Patent Application No. 16 / 898,569 [Patent Document 3] U.S. Patent No. 10,541,530 [Patent Document 4] U.S. Patent No. 10,276,321 Summary of the Invention [Means for solving the problem]

[0006] A self-diagnostic, self-maintaining, and self-protective solid-state circuit breaker (SSCB) is disclosed. An exemplary embodiment of the SSCB includes a power semiconductor device, an air gap disconnection unit connected in series with the power semiconductor device, a sensing and drive circuit that switches off the power semiconductor device upon detecting a short circuit or an overload of unacceptably long duration, and a microcontroller unit (MCU) that triggers the air gap disconnection unit to form an air gap and galvanically isolate an attached load after the sensing and drive circuit switches off the power semiconductor device. The MCU is further configured to monitor the operability of the air gap disconnection unit, the power semiconductor device, and other critical components of the SSCB and take corrective action, if applicable, to prevent damage or destruction of the SSCB and the connected load and / or to protect personnel and the environment from exposure to hazardous electrical conditions.

[0007] Further features and advantages of the present invention, including a detailed description of other exemplary embodiments summarized above, of the present invention, are described in detail with reference to the accompanying drawings, where like reference numbers are used to indicate identical or functionally similar elements. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a solid-state circuit breaker (SSCB) according to one embodiment of the present invention. [Figure 2] 2 is a perspective view of the SSCB shown in FIG. 1 revealing some of its salient components, in accordance with one embodiment of the present invention. [Figure 3] 2 is an exploded view of the SSCB shown in FIG. 1 further revealing some of its salient components, in accordance with one embodiment of the present invention. [Figure 4] 2 is a perspective view of an air gap disconnection unit of the SSCB shown in FIG. 1 in accordance with one embodiment of the present invention. [Figure 5]FIG. 2 is a front perspective view of the SSCB shown in FIG. 1 illustrating how the SSCB is preferably contained within a housing, revealing the SSCB's electronic display, on / off / standby button, and air gap disconnection unit reset and release buttons, in accordance with one embodiment of the present invention. [Figure 6] 2 is a line-side perspective view of the SSCB shown in FIG. 1 revealing the line-in terminal of the SSCB, in accordance with one embodiment of the present invention. [Figure 7] 2 is a load-side perspective view of the SSCB shown in FIG. 1 revealing the line-out terminal of the SSCB, in accordance with one embodiment of the present invention. [Figure 8] 1 is a flowchart illustrating how an MCU of an SSCB monitors core functionality of the SSCB and how the MCU responds when it determines that a core functionality of the SSCB has failed or may have failed, in accordance with one embodiment of the present invention. [Figure 9] 1 is a flowchart illustrating a method performed by an MCU of an SSCB to monitor and diagnose whether an air gap disconnection unit in the SSCB has failed closed or is likely to have failed closed, and the actions taken by the SSCB upon determining that the air gap disconnection unit has failed closed or is likely to have failed closed, in accordance with one embodiment of the present invention. [Figure 10] 1 is a flowchart illustrating a method performed by an MCU of an SSCB to monitor and diagnose whether an air gap disconnection unit in the SSCB has failed open or is likely to have failed open, according to one embodiment of the present invention, and the actions taken by the SSCB when it determines that the air gap disconnection unit has failed open or is likely to have failed open. [Figure 11] 1 is a flowchart illustrating a method performed by an MCU of an SSCB to monitor and diagnose the vitality, effectiveness, and operability of an air gap disconnection capacitor within the SSCB, and the actions taken by the SSCB when it determines that an air gap disconnection capacitor has failed or is failing. [Figure 12]A block diagram showing how, in one embodiment of an SSCB, the MCU of the SSCB is configured to generate a periodic heartbeat signal that is continuously monitored by an external watchdog circuit to verify the vitality and operability of the MCU. [Figure 13] 1 is a flowchart illustrating a method performed by an MCU of an SSCB to monitor the vitality, validity, and operability of an AC / DC converter of the SSCB, which serves as the primary DC power source for the MCU and other DC-powered electronics within the SSCB, and the actions taken by the SSCB upon determining that the AC / DC converter has failed or may be failing, in accordance with one embodiment of the present invention. [Figure 14] 1 is a flowchart illustrating a method performed by an MCU of a field effect transistor (FET) in an SSCB to monitor the vitality, validity, and operability of power FETs of a FET power module in the SSCB, and the actions taken by the MCU upon determining that one or more of the power FETs have failed, may have failed, or have failed, in accordance with one embodiment of the present invention. [Figure 15] 1 is a flowchart illustrating a method performed by an MCU of an SSCB to monitor the vitality, validity, and operability of power FETs of a FET power module of the SSCB, and the actions taken by the MCU upon determining that one or more of the power FETs has failed, is likely to have failed, or has failed, in accordance with one embodiment of the present invention. [Figure 16] 1 is a flowchart illustrating a method performed by an MCU of an SSCB in response to a sensed / measured power FET junction temperature sensed / measured by a thermistor mounted within a FET power module of the SSCB, and the actions taken by the MCU upon determining that the junction temperature, T, of one or more of the FETs in the FET power module has exceeded a predetermined maximum allowable junction temperature, T, in accordance with one embodiment of the present invention. [Figure 17]1 is a flowchart illustrating a method performed by an MCU of an SSCB to detect a failure or potential failure of one or more of the power FETs in a FET power module, and the actions taken by the MCU upon determining that one or more of the power FETs has failed, in accordance with one embodiment of the present invention. [Figure 18] 1 is a flowchart illustrating a method performed by an MCU of a single-phase version of an SSCB to detect a failed or potential failure of a power FET of the SSCB, and the actions taken by the MCU upon determining that a power FET has failed, is potential to have failed, or is potential to have failed, in accordance with one embodiment of the present invention. [Figure 19] 1 is a flowchart illustrating a method performed by an MCU of an SSCB to monitor the performance of and diagnose any failures of the lineout Hall effect sensors in the SSCB, and the actions taken by the MCU upon determining that one or more of the Hall effect sensors has failed, has failed, or is suspected of failing, in accordance with one embodiment of the present invention. [Figure 20] 1 is a flowchart illustrating a method performed by an MCU of an SSCB to verify that an air gap disconnection unit of the SSCB has successfully re-engaged in response to a person pressing a reset button on the SSCB, and the actions taken by the MCU when it determines that the air gap disconnection unit has not successfully re-engaged, in accordance with one embodiment of the present invention. [Figure 21] FIG. 1 is a schematic diagram illustrating the salient components of a FET power module of an SSCB, according to one embodiment of the present invention, highlighting the connectivity of the power FETs and the placement of various surge protection devices (SPDs) within the FET power module, according to one embodiment of the present invention. [Figure 22] 1 is a flowchart illustrating a method performed by an MCU in an SSCB to monitor the health of SPDs in a FET power module, and the actions taken by the MCU when it determines that one or more of the SPDs has failed, in accordance with one embodiment of the present invention. [Figure 23]1 is a flowchart illustrating a method performed by an MCU of an SSCB to monitor the operational status of one or more microswitches configured to indicate the physical displacement of an SSCB release button, according to one embodiment of the present invention, and the actions taken by the MCU upon determining that one or more of the one or more microswitches has failed. [Figure 24] FIG. 1 illustrates, in accordance with one embodiment of the present invention, multiple SSCBs configured in a distribution panel, how the SSCBs are in electrical communication with a communications and control (communications / control) bus having a head-end interface, and how an external, locally or remotely located computer (a tablet computer in the illustration) can be used to perform on-demand SSCB diagnostics and maintenance and to schedule periodic SSCB diagnostics and / or maintenance via a user-interactive graphical user interface (GUI). [Figure 25] FIG. 1 is a block diagram highlighting the salient components of an external, local or remotely controlled computer used to perform on-demand SSCB diagnostics and maintenance and to schedule periodic SSCB diagnostics and / or maintenance via a user-interactive GUI. DETAILED DESCRIPTION OF THE INVENTION

[0009] Referring to FIG. 1, a block diagram of a self-diagnostic, self-maintenance, and self-protection solid-state circuit breaker (SSCB) 100 according to one embodiment of the present invention is shown. The main components of the SSCB 100 include a microcontroller unit (MCU) 102, a sense and drive circuit 104, a field-effect transistor (FET) power module 106, and an air gap disconnection unit 108. The air gap disconnection unit 108 has three air gap contact switches 114, and the FET power module 106 has three power FETs 116, each configured such that its drain-source path is in series with one of the air gap contact switches 114. In other words, the FET power module 106 and the air gap disconnection unit 108 are connected in series between a line-in terminal 110 and a line-out terminal 112. During normal operating conditions, the three air gap contact switches in the air gap disconnection unit 108 are closed, and the three power FETs 116 in the FET power module 106 are on. This allows line current entering the line-in terminal 110 from a power source (e.g., alternating current (AC) distributed from within a distribution panel to the line-in terminal 110 of the SSCB 100) to flow to a load (not shown) connected to the line-out terminal 112 (e.g., via an electrical cable routed to a load in a commercial building or residence). However, if the SSCB 100 detects a short circuit or an overload of unacceptably long duration, the sense and drive circuit 104 switches off the power FET 116 to prevent any further current from flowing to the load. Meanwhile, or shortly after the power FET 116 is switched off, the MCU 102 generates a solenoid trigger signal, and the air gap disconnection unit 108 responds to the solenoid trigger signal to “disengage” and open the air gap contact switch 114, galvanically isolating the load. Note that the exemplary embodiment of the SSCB 100 shown in FIG. 1 and other figures of this disclosure is a three-phase device. It therefore has three line-in terminals 110 , three air-gap contact switches 114 , three power FETs 116 , and three line-out terminals 112 .A single-phase version of the SSCB would have only one of each of these components, as would be recognized and understood by those skilled in the art. It should also be noted that in a preferred embodiment of the present invention, the power FET 116 comprises a silicon carbide (SiC) MOSFET. However, as would be recognized and understood by those skilled in the art, other types of power semiconductor devices (e.g., GaN high electron mobility transistors (HEMTs)) could alternatively be used.

[0010] When the SSCB 100 is in a "tripped" state, the power FET 116 is perfectly capable of disconnecting the load from the input power source by itself. However, because government, regulatory, and certification agencies typically require that the load be galvanically isolated from the input power source when the circuit breaker is in a tripped state, the SSCB 100 preferably (though not necessarily in all embodiments of the invention) includes an air gap disconnection unit 108 that, when "disengaged," forms an air gap between the line-in terminal 110 and the line-out terminal 112. Among other components, the air gap disconnection unit 108 includes a large (i.e., high-capacity) air gap disconnection capacitor 117 (e.g., 10,000 microfarads or more), a solenoid 118, and a switch 120 that selectively couples the terminals of the air gap disconnection capacitor 117 across the coil of the solenoid 118. The physical relationship of the air gap disconnection capacitor 117 and solenoid 118 in one exemplary embodiment of the SSCB 100 can be seen in the perspective and exploded views of the SSCB 100 presented in FIGS. 2 and 3, as well as the perspective view of the air gap disconnection unit 108 alone in FIG. 4.

[0011] In one embodiment of the present invention, the air gap disconnection unit 108 is designed to be triggered to disengage and form an air gap between the line-in terminal 110 and the line-out terminal 112 automatically (by actuating the solenoid 118), manually (in response to a person depressing the release button 122, but without the aid of the solenoid 118), or in response to a command from a local or remote computer configured to interact with the SSCB 100 via a communications and control (com / control) bus 124. Automatic triggering occurs when the sense and drive circuit 104 detects a short circuit or other electrical anomaly (e.g., an overload of unacceptably long duration) in the load circuit of the SSCB 100. When this occurs, the sense and drive circuit 104 generates a gate disable signal and applies it to the gate of the power FET 116 in the FET power module 106, switching the power FET 116 off in just a few microseconds. The power FETs 116 can also be instructed to delay their switch-off to allow for switch-off during a zero-crossing of the current. The ability to switch off during current zero reduces disturbances in the upstream power system. During that time, or shortly after power FET 116 is switched off, MCU 102 generates a solenoid trigger signal that closes switch 120 (see FIG. 1 ) so that the terminals of air gap disconnection capacitor 117 are connected across the coil of solenoid 118. SSCB 100 is designed so that air gap disconnection capacitor 117 remains charged during normal operating conditions. In one embodiment of the present invention, AC / DC converter 126, which serves as the main DC power source for the DC-powered electronics within SSCB 100 (e.g., MCU 102, CRM 103, and DC components on sense and drive circuit board 104), is further configured to charge air gap disconnection capacitor 117 and maintain it in a fully charged state. Thus, when a solenoid trigger signal is applied to switch 120 to close it, and the terminals of air gap disconnect capacitor 117 are then connected across the coil of solenoid 118, a large current begins to flow through the coil of the solenoid.The large coil current, in turn, generates a magnetic field that causes the solenoid 118 to pull its plunger 128 into the solenoid's housing. As the plunger 128 is retracted into the solenoid housing, it engages a latch 130, which rotates about a pivot axis and swings away from an upper lip 132 of a holster 136. (See FIGS. 2-4.) Under normal operating conditions, the latch 130 is positioned to hold down the holster 136 (by depressing the upper lip 132), thereby keeping the air gap contact switch 114 closed. However, when the solenoid 118 is triggered, causing the plunger 128 of the solenoid 118 to rotate the latch 130 and swing it away from the upper lip 132, the latch 130 no longer holds down the holster 136, and the normally compressed breaker spring 138 decompresses, pushing the holster 136 upward. Pushing up on holster 136 opens air gap contact switch 114, resulting in the formation of an air gap between line-in terminal 110 and line-out terminal 112. This air gap galvanically isolates the load from the input power applied to line-in terminal 110, so that with power FET 116 off and air gap disconnection unit 108 disengaged from the air gap formed between line-in terminal 110 and line-out terminal 112, SSCB 100 is fully "tripped."

[0012] In one embodiment of the present invention, the air gap disconnection unit 108 is further designed to be disengaged manually, specifically, in response to a person depressing a release button 122. When a person depresses the release button 122, a coupling member 140 (see FIGS. 2-4 ) presses against a cam surface 142 on the latch 130, rotating the latch 130 and disengaging it from the upper lip 132 of the holster 136, allowing the normally compressed disconnect spring 138 to decompress and lift the holster 136, opening the air gap contact switch 114 and creating an air gap. As the holster 136 is lifted, it also presses against and lifts the reset button 144 to expose a lockout-tagout (LOTO) hole 146 through which a service or maintenance (service / maintenance) worker can insert a padlock or other locking device to complete the LOTO safety procedure. Note that the reset button 144 pops up to reveal the LOTO hole 146 whether the air gap disconnection unit 108 is triggered to automatically disengage (by the MCU 102 actuating the solenoid 118) or manually (by a person pressing the release button 122). Completing the LOTO safety procedure ensures that a service / maintenance worker or other person does not inadvertently or accidentally re-engage the air gap disconnection unit 108. After the service / maintenance is completed, the service / maintenance worker can then re-engage the air gap disconnection unit 108 by removing the padlock or other locking device and pressing the reset button 144. When the reset button 144 is pressed, it engages the holster 136 and recompresses the disconnect spring 138. It also engages the rotary latch 130 to re-engage the top lip 132 of the holster 136 to again hold down the holster 136 and close the air gap contact switch 114.Further details of the SSCB 100, including a similar air gap disconnection unit, can be found in co-pending, commonly assigned U.S. patent application Ser. No. 16 / 898,538, entitled "Solid-State Circuit Breaker with Galvanic Isolation," which is incorporated herein by reference.

[0013] It should be mentioned that the SSCB 100 preferably includes an additional lockout mechanism 160 that can be activated by the SSCB 100 itself (i.e., without any human intervention) to prevent the reset button 144 from being pressed and the air gap disconnection unit 108 from re-engaging, if conditions permit. This additional lockout mechanism 160 can be activated by the SSCB 100 regardless of whether a padlock or other locking device is inserted through the LOTO hole 146 of the reset button 144. In one embodiment of the present invention, the additional lockout mechanism 160 includes a secondary solenoid that is smaller in size compared to the primary solenoid 118 used to disengage the air gap disconnection unit 108. After the MCU 102 determines that a major component or critical function of the SSCB 100 has failed or may have failed and the MCU 102 triggers the primary solenoid 118 to disengage the air gap disconnection unit 108 (e.g., after performing one of the various self-diagnostic, self-maintenance, and self-protection methods described herein), the MCU 102 triggers the secondary solenoid. The plunger of the secondary solenoid is configured to engage the reset button 144 (or engage some other mechanical linkage connected to the reset button 144) and prevent the reset button 144 from being depressed into the housing of the SSCB 100. Thus, the secondary lockout mechanism 160 prevents a person from attempting to re-engage the air gap disconnection unit 108 after the SSCB 100 has determined that a potentially unsafe condition exists and / or that its major component or critical function has failed or may have failed.

[0014] 1 and 2, MCU 102 is mounted on control board 105 along with computer-readable memory (CRM) 103. CRM 103 comprises flash memory and / or electrically erasable read-only memory (EPROM) for storing firmware and software that directs the operation of MCU 102, and random access memory (RAM) utilized by MCU 102 in executing firmware and software instructions. As will be appreciated by those skilled in the art, CRM 103 may be external to MCU 102 (as shown in FIG. 1), embedded within MCU 102, or comprise computer-readable memory that is partially embedded within MCU 102 and partially external to the MCU.

[0015] Preferably, SSCB 100 includes human-depressible on button 107, off button 109, and standby button 111 (on / off / standby), enclosed within a housing (i.e., "enclosure"), as shown in FIGS. 5-7, and electronic display 113. In one embodiment of SSCB 100, electronic display 113 is an electronic ink display, a display technology that allows currently displayed information to remain visible even if power to the display is interrupted or completely removed. (Note that ribbon cable 119 (see FIG. 2) provides electrical connectivity between control board 105 and on / off / standby buttons 107, 109, and 111.) In one embodiment of the present invention, on / off / standby buttons 107, 109, and 111 are translucent and colored green, red, and yellow, respectively, and light-emitting diodes (LEDs) (not shown in the drawings) are configured beneath each button. The LEDs indicate and highlight the current state of SSCB 100, regardless of which LED is lit. Specifically, when the ON button 107 (a green-colored button with an "I" indicator) is pressed ON and the LED below it is lit, the green highlighting indicates that the SSCB 100 is fully operational (the air gap disconnection unit 108 is engaged (the air gap contact switch 114 is closed) and the power FET 116 in the FET power module 106 is ON). When the STANDBY button 109 (a yellow button marked with an "X") is pressed and the LED below it is lit, the yellow highlighting indicates that the SSCB 100 is in a STANDBY state (the air gap disconnection unit 108 is engaged, but the power FET 116 in the FET power module 106 is OFF). (Note that a transition from the STANDBY state to the ON state can be made, if desired, by simply pressing the ON (green) button 107.)11.) Finally, the off red button 111, which is not actually a depressible button in the exemplary embodiment of the SSCB 100 described herein (but could be in alternative designs), is illuminated by an LED located below it both when the air gap disconnection unit 108 is disengaged (when the air gap contact switch 114 is open) and when the power FET 116 in the FET power module 106 is off. The red highlighting indicates that the SSCB 100 is “tripped,” or fully off (the power FET 116 in the FET power module 106 is off and the air gap disconnection unit 108 is disengaged). The reason the off red button 111 does not need to be a depressible button is that its functionality is already provided by the release button 122, which, when pressed, causes the SSCB's electronics and driver circuitry to switch off the power FET 116 in the FET power module 106 and then immediately triggers the air gap disconnection unit 108 to disengage.

[0016] 7, a perspective view of the load side of the encapsulated SSCB 100, shows, in this particular exemplary embodiment, the line-out terminal 112, which includes a load-side connection lug 148 to which a power cable may be connected and routed to the load. FIG. 7 also shows a communication and control (communication / control) bus shield 150, which protects the electrical communication / control bus connector connecting the SSCB 100 to the communication / control bus 124 when the SSCB 100 is installed in a distribution panel, similar to that described in co-pending and commonly assigned U.S. patent application Ser. No. 16 / 898,569, entitled "Distribution Panel for Intelligently Controlled Solid-State Circuit Breakers," which is incorporated herein by reference. The communication / control bus 124, which may be an Inter-IC (I2C) or Controller Area Network (CAN) bus, provides the SSCB 100 with the ability to communicate with and be controlled by a local or remote computer, similar to, for example, those described in commonly assigned U.S. Pat. No. 10,541,530, entitled "Hybrid Air-Gap / Solid-State Circuit Breaker," and commonly assigned U.S. Pat. No. 10,276,321, entitled "Dynamic Coordination of Protection Devices in Electrical Distribution Systems," both of which are incorporated herein by reference. The communication / control bus 124 also provides the SSCB 100 with the ability to report the operational status of the SSCB 100 to a local or remote computer (in real time or non-real time), for example, after running a set of scheduled or on-demand diagnostic tests, as described in more detail below.

[0017] Control board 105 serves as the "brains" of SSCB 100 and, in one exemplary embodiment of SSCB 100, includes MCU 102 and CRM 103. Firmware and other computer program instructions (i.e., software) stored within CRM 103 and retrieved and executed by MCU 102 control the general operation of SSCB 100 and include instructions that determine whether, how, and when MCU 102 interacts with other components within SSCB 100, as well as instructions and protocols that allow MCU 102 to communicate with and be controlled by other devices (e.g., external computers) via communication / control bus 124. In some embodiments of the SSCB 100, the computer program instructions, when executed by the MCU 102, provide: 1) the ability to monitor and diagnose the vitality, validity, and operability of the air gap disconnection unit 108, including determining if the air gap disconnection unit 108 has failed to open or close, when appropriate or necessary; 2) the ability to monitor and diagnose the vitality, validity, and operability of the power FETs 116 in the FET power module 106, and direct the sense and drive circuitry 104 to switch the power FETs 116 off, when conditions permit; and 3) the ability to trigger a solenoid to disengage the air gap disconnection unit 108 and form an air gap between the line-in terminal 110 and the line-out terminal 112, when conditions permit. 4) the ability to monitor the vitality, viability, and operability of the AC / DC converter 126 and instruct the sense and drive circuitry 104 to switch off the power FET 116 (using energy stored in the air gap disconnection capacitor 117, if necessary) if the AC / DC converter 126 is determined to have failed or is failing; 5) the ability to monitor and diagnose the vitality, viability, and operability of the air gap disconnection capacitor 117 and generate a capacitor bypass signal that allows the AC / DC converter 126 to bypass the air gap disconnection capacitor 117 if the MCU 102 determines that the air gap disconnection capacitor 117 has failed or is failing; and 6) the ability to monitor the vitality, viability, and operability of the MCU 102 to generate a capacitor bypass signal that allows the AC / DC converter 126 to bypass the air gap disconnection capacitor 117.7) the ability to monitor and diagnose failures, and possible or probable failures, of the current and voltage sensors 154 and 156 used to sense the line current and voltage at the input and output of the FET power module 106; 8) the ability to monitor the vitality, effectiveness, and operability of surge protection devices (SPDs) that function to prevent the power FETs 116 from being exposed to high voltages, and to shut down the SSCB 100 if one or more of the SPDs fail or degrade beyond their usefulness; and 9) the ability to monitor the vitality, effectiveness, and operability of the SSCB 100 and its various components. The exemplary SSCB 100 further includes instructions to provide the MCU 102 with the following capabilities: 1) the ability to direct and control the electronic display 113 of the SSCB 100 to display information (both real-time and non-real-time) regarding the vitality, effectiveness, and operability of the SSCB 100; 2) the ability to report information (both real-time and non-real-time) regarding the vitality, effectiveness, and operability of the SSCB 100 to a system supervisor (e.g., an electrician, home / building owner, or electric utility) via the communication / control bus 124; and 3) the ability to recommend corrective actions that the system supervisor may take to address or remedy any particular fault or problem that the SSCB 100 may have experienced or is currently experiencing. A recommended corrective action may include, for example, turning off an upstream circuit breaker (which may be an SSCB similar in construction to the exemplary SSCB 100 described herein) based on a fault diagnosed at the downstream SSCB. Taking such corrective action reduces risk to downstream equipment should a fault impair or eliminate the protective function of the downstream SSCB. These and other functions and capabilities of the SSCB 100 are discussed in further detail below.

[0018] 8 is a flowchart illustrating a method 800 executed by the MCU 102 (together with other cooperating components of the SSCB 100) to verify the basic (i.e., "core") functionality of the SSCB 100, and the actions the MCU 102 takes upon determining that the SSCB 100's core functionality has failed or may have failed, specifically, to trip when required. According to this method, the SSCB 100 is assumed to be configured in a power distribution system having an input power source (e.g., AC mains) attached to the SSCB's line-in terminal 110 and a load attached to the line-out terminal 112. First, in step 802, the SSCB 100 is switched on (the power FET is closed and the air gap disconnection unit is engaged (no air gap)). In step 804, the MCU 102 reduces the SSCB 100's trip threshold to and beyond the load's nominal current. If the SSCB's core functionality is operating properly, the SSCB 100 should trip (the power FET 116 opens and the air gap disconnection unit disengages) because the trip threshold is adjusted below the nominal load current. Step 806 is executed to determine whether the SSCB tripped as intended. Specifically, in step 806, the MCU 102 determines the voltage difference ΔV between the line-in terminal 110 and the line-out terminal 112. If, in decision 808, it is determined that ΔV is sufficiently greater than zero to indicate galvanic isolation of the load ("YES" in decision 808), the MCU 102 can properly conclude that the SSCB's core functionality is operating correctly, and in step 810, the trip threshold is returned to normal, and in step 812, the power FET 116 is quickly switched on (thus briefly interrupting current to the load during the test), the air gap disconnection unit 108 is re-engaged to close the air gap, and the method 800 ends.However, if, in decision 808, the MCU 102 determines that the ΔV between the line-in terminal 110 and the line-out terminal 112 is zero or not sufficiently greater than zero to indicate adequate galvanic isolation (“NO” in decision 808), the MCU 102 concludes that the SSCB's core functionality has failed and, in step 814, alerts a system monitor that the SSCB's core functionality has failed. The failure of the SSCB's core functionality may be due, for example, to a damaged power FET 116 in the FET power module 106, a malfunctioning air gap disconnection unit 108, a damaged or destroyed sense and drive circuit 104, damaged current and / or current and voltage sensors 154 and 156, or may be caused by some other damaged or malfunctioning component. In some embodiments of the invention, the MCU 102 reports the failure to a remote computer via the communication / control bus 124 and / or instructs the SSCB to display the failure information on the SSCB's electronic display 113. To further isolate and identify the source of the core functionality failure, some or more diagnostic tests, discussed below, may be performed following a "NO" at decision 808.

[0019] In this illustrated core functionality diagnostic method 800, the air gap disconnection unit 108 must be re-engaged (e.g., by the user pressing the reset button 144) after the core functionality of the SSCB 100 is verified (i.e., following a "YES" at decision 808). In an alternative method, the MCU 102 does not trigger the air gap disconnection unit 108 to disengage during the core functionality diagnostic check, but instead maintains the air gap disconnection unit 108 in the engaged position (no air gap between the line-in terminal 110 and the line-out terminal 112) throughout the test. According to this alternative approach, if, at decision 808, the MCU 102 determines that ΔV is zero or not sufficiently greater than zero (“NO” at decision 808), the MCU 102 can appropriately conclude that one or more of the power FETs 116 has failed and / or one or more of the current / voltage sensors 154 and 156 has failed or may have failed, and then, at step 814, a system monitor is alerted to the failure or possible failure. One advantage of this alternative core functionality diagnostic check is that a person (i.e., a “user”) does not need to re-engage the air gap disconnection unit 108 following the diagnostic check (because the MCU 102 does not trigger the air gap disconnection unit 108 to disengage during the check). Another advantage is that the speed of the diagnostic check is much faster, thereby causing an almost imperceptible effect on current flow to the load, compared to an approach in which the air gap disconnection unit 108 is disengaged and then re-engaged. It should also be pointed out that this alternative core function diagnostic check may also be advantageously used in embodiments of the SSCB 100 that do not include the air gap disconnection unit 108, i.e., those that include only power semiconductors between the line-in terminal 110 and the line-out terminal 112, and therefore rely solely on the power semiconductors to disconnect the load in the event of a fault or overload.

[0020] FIG. 9 (including FIGS. 9A and 9B) is a flowchart of a method 900 that the MCU 102 (along with other cooperating components of the SSCB 100) performs to monitor and diagnose the vitality, effectiveness, and operability of the air gap cutting unit 108, specifically, to monitor and diagnose whether the air gap cutting unit 108 has failed closed (presumably because one or more of the air gap contact switches 114 have closed and failed without the ability to open again), and how the SSCB 100 responds after the MCU 102 determines that the air gap cutting unit 108 has actually failed closed. According to this method 900, the MCU 102 is also provided with the ability to detect possible failures of the line-in current / voltage sensor 154 and / or the line-out current / voltage sensor 156. In step 902, the MCU 102 commands the air gap cutting unit 108 to disengage and form an air gap (by closing the switch 120, connecting the air gap cutting capacitor 117 across the coil of the solenoid 118, and generating a solenoid trigger signal to open the air gap contact switch 114 as described above), and after the air gap is formed, commands the sense and drive circuit 104 to switch the power FET 116 on. In steps 904 and 906, the input and output voltages for all three phases are measured on both the line-in side and the line-out side of the FET power module 106. The sensed / measured line-in voltage and line-out voltage are directed to the MCU 102, and in step 908, the MCU 102 compares the line-in voltage V(line-in) with the line-out voltage V(line-out) for each phase, or calculates the difference between them. Then, in decision 910, if the MCU 102 determines that V(line-in) < V(line-out) for any given phase (''YES'' in decision 910), the MCU 102 can appropriately conclude that the air gap cutting unit 108 has failed closed and / or that one or more of the line-in current / voltage sensor 154 and the line-out current / voltage sensor 156 have failed.To rule out the possibility that one or more of the line-out current / voltage sensors 156 have failed, steps 912 and determination 914 are executed. Specifically, in step 912, the MCU 102 instructs the sense and drive circuit 104 to switch off the power FET 116 in the phase where V(line-in) < V(line-out) has been determined. Next, the line-out current / voltage sensor 156 measures V(line-out) at the output of the power FET 116 that has just been switched off, and in determination 914, the MCU 102 determines whether V(line-out) has gone low. If V(line-out) has gone low, the MCU 102 can conclude that the air-gap disconnection unit 108 is closed and malfunctioning, and that one or more of the line-in current / voltage sensors 154 may have failed. Since both are serious problems, in step 916, the MCU 102 instructs the sense and drive circuit 104 to switch off the remaining power FETs 116, preventing any further attempts to switch the power FETs 116 on, and in step 918, reports to the system monitor that the air-gap disconnection unit 108 is closed and malfunctioning, and that one or more of the line-in current / voltage sensors 154 may also have failed. The MCU 102 may also report the failure or potential failure, as indicated by step 918, to a remote computer via the communication / control bus 124, and / or instruct the display of the SSCB 100 to display the failure information on its electronic display 113.

[0021] If V(lineout) does not go low at decision 914 (“NO” at decision 914), the MCU 102 can conclude that the air gap disconnection unit 108 is closed and not faulty, but that one or more of the lineout current / voltage sensors 156 may have failed. Accordingly, at step 922, the MCU 102 instructs the sense and drive circuit 104 to switch off the remaining power FETs 116, inhibiting the air gap disconnection unit 108 from re-engaging and preventing any further attempts to switch on the power FETs 116. In this state, the SSCB 100 is locked down until it can be serviced / repaired by a qualified electrician or engineer. Finally, at step 924, the MCU 102 reports the likely failure of one or more of the lineout current / voltage sensors 156 to a system supervisor and / or instructs the SSCB 100 to indicate on its electronic display 113 that one or more of the lineout current / voltage sensors 156 may have failed.

[0022] If, at decision 910, the MCU 102 determines that V(line in) is greater than or equal to V(line out) for any of the three phases (“NO” at decision 810), the MCU 102 can properly conclude that the air gap disconnection unit 108 is closed and not faulted, and that the line-in current / voltage sensors 154 are operating as intended. However, that determination does not, in itself, rule out the possibility that one or more of the line-out current / voltage sensors 156 have failed. To ensure that the line-out current / voltage sensors 156 are operating as intended, decision 920 is performed, specifically querying whether V(line in) > V(line out) for any given phase. If V(line-in) > V(line-out) for any given phase ("YES" at decision 920), the MCU 102 can properly conclude that the air gap disconnection unit 108 is closed and not faulted, the line-in current / voltage sensor 154 is operating as intended, but one or more of the line-out current / voltage sensors 156 may have failed. Accordingly, step 922 is performed to shut down the SSCB 100, and finally, in step 924, the MCU 102 reports the likely failure of one or more of the line-out current / voltage sensors 156 to a system monitor and / or instructs the SSCB 100 to indicate on its electronic display 113 that one or more of the line-out current / voltage sensors 156 may have failed.

[0023] In addition to being programmed to monitor and diagnose whether the air gap disconnection unit 108 has failed closed, in one embodiment of the present invention, the MCU 102 is also programmed to monitor and diagnose whether the air gap disconnection unit 108 has failed open. Figure 10 (including Figures 10A and 10B) is a flowchart of a method 1000 performed by the MCU 102 (along with other cooperating components of the SSCB 100) in this regard. Prior to the start of method 1000, it is assumed that all of the power FETs 116 are on and the air gap disconnection unit 108 is engaged (air gap contact switch 114 is closed). Then, in steps 1002 and 1004, the input and output voltages for all three phases are measured on both the line-in and line-out sides of the FET power module 106. At decision 1006, using the current / voltage measurements received from the line-in current / voltage sensor 154 and the line-out current / voltage sensor 156, the MCU 102 determines whether there is no measurable voltage on both the line-in and line-out sides of the FET power module 106 for any given phase. If there is (“YES” at decision 1006), the MCU 102 can conclude that one or more phases of the air gap disconnection unit 108 have failed open. Accordingly, at step 1008, the MCU 102 reports to a system monitor via the communication / control bus 124 that one or more phases of the air gap disconnection unit 108 have failed open.

[0024] If the MCU 102 determines that there is not a measurable voltage on both the line-in and line-out sides of the FET power module 106 for each of the three phases (“NO” at decision 1006), it may still be possible that one or more of the line-in current / voltage sensors 154 and line-out current / voltage sensors 156 have failed or are failing. Steps 1010-1022 are performed to further identify and isolate any failed or potentially failing line-in current / voltage sensors 154 or line-out current / voltage sensors 156. Specifically, at decision 1010, the MCU 102 determines whether a voltage mismatch exists between the line-in and line-out voltages on any of the three phases from the line-in and line-out voltage measurements taken by the line-in current / voltage sensors 154 and line-out current / voltage sensors 156. If "NO," the MCU 102 may conclude that all of the line-in and line-out voltage sensors 154 and 156, and the air gap disconnection unit 108, are all working properly, and method 1000 ends. On the other hand, if, at decision 1010, the MCU 102 determines that a voltage mismatch exists between the line-in and line-out voltages in any of the three phases ("YES" at decision 1010), the MCU 102 may appropriately conclude that one or more of the voltage sensors 154 and / or 156 has failed or may be failing. To determine whether the failed or failing voltage sensor in any faulty phase is the line-in current / voltage sensor 154 or the line-out voltage sensor 156, in step 1012, the MCU 102 instructs the sense and drive circuit 104 to switch off the power FET 116 in each phase in which one or more of the voltage sensors 154 and / or 156 were determined to have failed or may have failed in decision 1010, and then in decision 1014, the MCU 102 determines whether V(line-out) goes low or remains high in each of these phases.If V(lineout) does not go low on any of the phases (“NO” at decision 1014), the MCU 102 concludes that one or more of the lineout voltage sensors 156 has failed or may have failed and / or one or more of the power FETs 116 has failed, and in accordance with that determination, prevents any further attempts to switch on the power FETs 116 at step 1016. Then, at step 1018, the MCU 102 reports to a system monitor that one or more of the lineout voltage sensors 156 has failed or may have failed and / or that one or more of the power FETs 116 has failed, and / or instructs the electronic display 113 of the SSCB 100 to indicate that one or more of the lineout voltage sensors 156 has failed or may have failed and / or that one or more of the power FETs 116 has failed. On the other hand, if the MCU 102 determines in decision 1014 that V(line out) went low on all phases after the power FETs 116 were switched off in step 1012 (“YES” in decision 1014), the MCU 102 concludes that one or more of the line-in voltage sensors 154 has failed or may be failing. Pursuant to that determination, in step 1020, the MCU 102 prevents any further attempts to switch on the power FETs 116. Finally, in step 1022, the MCU 102 reports to a system monitor that one or more of the line-in current / voltage sensors 154 has failed or may be failing and / or instructs the electronic display 113 of the SSCB 100 to indicate that one or more of the line-in voltage sensors 154 has failed or may be failing.

[0025] The solenoid 118 in the air gap disconnection unit 108 requires a significant amount of energy to drive the air gap disconnection unit 108 open. To avoid undesirable dips in the DC voltage VDC generated by the AC / DC converter 126 (which, as described above, serves as a DC power source for the DC electronics in the SSCB 100, including the MCU 102, CRM 103, and DC components on the sense and drive circuitry 104), a large air gap disconnection capacitor 117 is used as the energy source to trigger the solenoid 118. (Note: In some embodiments of the present invention, the air gap disconnection capacitor 117 is also configured to function as a backup DC power source for short durations, providing a backup DC voltage VDC (backup) in the event that the DC voltage VDC generated by the AC / DC converter 126 is lost.) In one embodiment of the present invention, the MCU 102 is programmed to monitor and diagnose the vitality, availability, and operability of the air gap disconnection capacitor 117, and to generate a capacitor bypass signal that enables the AC / DC converter 126 to bypass the air gap disconnection capacitor 117 when the air gap disconnection capacitor 117 has failed or is determined to be failing. FIG. 11 is a flowchart illustrating this method 1100. Method 1100 is performed as the air gap disconnection capacitor 117 charges, and in particular, each time the SSCB activates and each time it recharges after being discharged by the firing of the solenoid 118 in the air gap disconnection unit 108. During a first step 1102, as the air gap disconnection capacitor 117 charges, the MCU 102 measures the charge voltage rate dV / dt (measured). In step 1104, MCU 102 compares the measured charge rate dV / dt (measured) with the expected (predetermined) charge rate dV / dt (expected), and then in decision 1106 determines whether dV / dt (measured) significantly exceeds or significantly falls below the expected charge rate dV / dt (expected).If not (“NO” at decision 1106), the MCU 102 can conclude that the air gap disconnection capacitor 117 is operating properly, and method 1100 ends. On the other hand, if, at decision 1106, the MCU 102 determines that the measured charge rate dV / dt (measured) is significantly greater than or significantly less than the expected charge rate dV / dt (expected) (“YES” at decision 1106), then at step 1108, the MCU 102 concludes that the air gap disconnection capacitor 117 has failed or may be failing, and the MCU 102 generates and applies a cap bypass control signal that closes the cap bypass switch 123 (see FIG. 1 ) to bypass the air gap disconnection capacitor 117. In this bypass configuration, the AC / DC power converter 126 is used to trigger the air gap disconnection unit 108. Because this is not the preferred configuration (it is instead preferable to use the energy stored in the air gap disconnection capacitor 117 to trigger the air gap disconnection unit solenoid 118), in step 1110 the MCU 102 reports to the system monitor that the air gap disconnection capacitor 117 has failed or may have failed and needs to be replaced. Additionally (or alternatively), the MCU 102 may also instruct the electronic display 113 of the SSCB 100 to indicate that the air gap disconnection capacitor 117 has failed or may have failed.

[0026] Since the MCU 102 is the "brains" of the SSCB 100, it is important that it does not fail, but if it does fail, it is preferable to have some way to trip the SSCB 100 without the necessary assistance of the MCU 102. To achieve this goal, as shown in Figure 12, in one embodiment of the present invention, the MCU 102 is programmed to generate a periodic "heartbeat" (e.g., a 10 kHz square wave) at one of its outputs. The heartbeat is fed to the input of an external "watchdog" 1202, which generates an output signal that switches off the power FET 116 (or is used to instruct the sense and drive circuit 104 to switch off the power FET 116). Additionally, the watchdog 1202 generates a solenoid trigger signal that triggers the air gap disconnection unit 108 to disengage (open the air gap contact switch 114), similar to how the MCU 102 generates a solenoid trigger signal that triggers the air gap disconnection unit 108 to disengage when the MCU 102 is operating properly. Alternatively, the watchdog 1202 is configured to first attempt to reset the MCU 102 before switching off the power FET 116 and before triggering the air gap disconnection unit 108. The watchdog 1202 may be constructed in a variety of ways. In one embodiment of the present invention, the watchdog 1202 comprises a counter and a flip-flop that together monitor the heartbeat of the MCU 102 and generate a disable signal to switch off the power FET 116 and disengage the air gap disconnection unit 108 when the heartbeat flattens or becomes irregular or aperiodic.

[0027] In an exemplary embodiment of the SSCB100 described herein, the AC / DC converter 126 (see FIG. 1) functions as a primary DC power source for the MCU 102, the CRM 103, the sensing and driving circuit 104, and other DC-driven electronics within the SSCB100. In one embodiment of the present invention, the AC input power to the AC / DC converter 126 is the AC main power supply power supplied by the AC main power supply. Therefore, it is important to monitor the presence of the AC main power supply power and the vitality and operability of the AC / DC converter 126 to ensure the intended proper operation of the SSCB100 and to take appropriate measures when the AC input power is lost and / or the AC / DC power converter 126 fails. In one embodiment of the present invention, the presence of the AC input power is continuously monitored, and the vitality, effectiveness, and operability of the AC / DC converter 126 are also monitored. If it is determined that there is no AC input power and / or it is determined that the AC / DC converter 126 has failed or may have failed, the MCU 102 instructs the sensing and driving circuit 104 to switch off the power FET 116 (using, if necessary, the energy stored in the air gap cut-off capacitor 117). FIG. 13 is a flowchart further illustrating this method 1300. While monitoring the DC output voltage VDC of the AC / DC converter 126 in step 1302, in determination 1304, the MCU 102 determines whether VDC is less than a certain low DC threshold VDC (threshold), that is, determines whether VDC < VDC (threshold). If the MCU 102 determines that VDC has dropped below the threshold VDC (threshold) (''YES'' in determination 1304) and remains below the threshold for a duration longer than a certain predetermined duration, and in determination 1306, if the MCU 102 also determines that AC power is present at the input of the AC / DC converter 126, the MCU 102 can appropriately conclude that the AC / DC converter 126 has failed or may have failed.Thus, in step 1312, the MCU 102 instructs the sense and drive circuit 104 to switch the power FET 116 off and generates a solenoid trigger signal that causes the air gap disconnection unit 108 to disengage and open the air gap contact switch 114, preventing any further attempts to switch the power FET 116 on and re-engage the air gap disconnection unit 108 until an electrician or engineer can be dispatched to replace the SSCB 100 or remove the faulty or failing AC / DC converter 126 and replace it with a functioning one. If, in decision 1306, the MCU 102 determines that AC power is not present at the input of the AC / DC converter 126, the MCU 102 cannot conclude that a faulty or failing AC / DC converter 126 has caused VDC to drop below the threshold VDC(threshold). In step 1312, the current state of the SSCB 100 may be stored in the flash memory portion of the CRM 103 of the SSCB 100 so that the SSCB 100 can resume its normal operation when AC power is restored.

[0028] The air gap disconnection unit 108 is designed to galvanically isolate the load when the SSCB 100 detects an unacceptably long-duration fault or overload. To prevent arcing across the air gap, the power FETs 116 are preferably switched off before the air gap disconnection unit 108 completes forming the air gap between the line-in terminal 110 and the line-out terminal 112. To achieve this safety feature, in one embodiment of the present invention, the MCU 102 is programmed to continuously monitor the vitality, validity, and operability of the power FETs 116. If the MCU 102 then determines that one or more of the power FETs 116 have failed (or may be failing), it is inhibited from generating a solenoid trigger signal that triggers the air gap disconnection unit 108 to open the air gap contact switch 114. FIG. 14 is a flowchart illustrating this method 1400 in more detail. First, in step 1402, the power FETs 116 in the FET power module are switched off. Then, in steps 1404 and 1406, the current / voltage sensors 154 and 156 sense / measure the voltage for each phase on both the line-in and line-out sides of the FET power module 106. Then, using the measured voltages, in step 1408, the MCU 102 determines whether there is a voltage drop ΔV across the drain-source terminals of any one of the power FETs 116. Because the power FETs 116 were switched off in step 1402, a voltage ΔV should be present. If it is determined that a voltage ΔV is present (“YES” at decision 1410), the MCU 102 can properly conclude that the power FET 116 is indeed switched off and operating as intended, and method 1400 ends.However, if the MCU 102 determines that no voltage drop ΔV or only a very small voltage drop ΔV appears across any one of the drain-source terminals of any one of the power FETs 116 (“NO” at decision 1410), the MCU 102 may conclude that one or more of the power FETs 116 has failed closed (or may have failed closed or has failed closed). Following this determination at step 1412, the MCU 102 then prevents the air gap disconnection unit 108 from disengaging (so that arcing cannot occur between the line-in terminal 110 and the line-out terminal 112) and prevents any further attempts to switch on the power FETs 116. Finally, in step 1414, the MCU 102 reports to a system monitor that one or more of the power FETs 116 have failed (or may have failed or have failed) and / or instructs an electronic display on the SSCB 100 to indicate that one or more of the power FETs 116 have failed (or may have failed or have failed).

[0029] As an alternative to the method 1400 shown in Figure 14, after determining in decision 1410 that ΔV is equal to or slightly greater than zero, the MCU 102 is programmed to instruct the air gap disconnection unit 108 to trigger and form an air gap only if the air gap disconnection unit 108 has not yet exceeded some predetermined maximum number of air gap arc exposures. In this manner, an air gap may be beneficially formed between the line-in terminal 110 and the line-out terminal 112 to galvanically isolate the load if one or more of the power FETs 116 fail closed and as long as the maximum number of air gap arc exposures has not been reached. Figure 15 is a flowchart illustrating this alternative method 1500. First, after determining in decision 1410 that ΔV is not greater than zero, the MCU 102 determines in decision 1502 whether the predetermined maximum number of air gap arcs has been reached. If not ("NO" at decision 1502), then in step 1504, MCU 102 commands air gap disconnection unit 108 to form an air gap between line-in terminal 110 and line-out terminal 112, despite the fact that one or more of power FETs 116 may have failed closed, and despite the possibility of arcing occurring between line-in terminal 110 and line-out terminal 112. Then, in step 1506, MCU 102 reports the likely power FET failure to a system monitor and / or instructs electronic display 113 of SSCB 100 to indicate that one or more of power FETs 116 have failed or may have failed. On the other hand, if, at decision 1502, the MCU 102 determines that the predetermined maximum number of air gap arcs has been reached (“YES” at decision 1502), then, at step 1508, the MCU 102 triggers the mechanical lockout mechanism 160 to ensure that the air gap disconnection unit 108 cannot be re-engaged.

[0030] In a preferred embodiment of the SSCB 100, a positive temperature coefficient (PTC) thermistor 152 (see FIG. 1) is mounted within the FET power module 106 as close as possible to each of the power FETs 116. The thermistor 152 is configured to measure and report the real-time operating temperature of the power FETs 116, and the MCU 102 is configured to receive and respond to the temperature measurements according to a method 1600 shown in FIG. 16. Specifically, in response to the sensed / measured power FET junction temperature sensed / measured by thermistor 152 and reported to the MCU 102 (step 1602), the MCU 102, in step 1604, calculates the sensed / measured junction temperature T J is the maximum allowable junction temperature T MAX Is it higher than T? J >T MAX If not (“NO” at decision 1604), the method 1600 loops back to step 1602. However, if the MCU 102 detects a sensed / measured junction temperature T J is the maximum allowable junction temperature T MAX ("YES" at decision 1604), the MCU 102 may conclude that a possible thermal runaway condition is occurring in one or more of the power FETs 116. To prevent damage to the power FETs 116 and / or possibly other components within the SSCB 100, in step 1606 the MCU 102 commands the air gap disconnection unit 108 to disengage and interrupt current flow through the power FETs 116, and in step 1608 the MCU 102 reports to a system monitor that a thermal runaway condition may have occurred and / or instructs the electronic display 113 of the SSCB 100 to indicate that a probable thermal runaway condition may have occurred. Additionally (or alternatively), the MCU 102 may also instruct the sense and drive circuit 104 to switch off the power FETs 116.

[0031] In an exemplary embodiment of the SSCB 100 disclosed herein, line-in and line-out current and voltage (current / voltage) sensors (e.g., Hall-effect sensors) 154 and 156 are configured near or at the input and output of the FET power module 106. These measurements enable the MCU 102 to determine whether any one of the power FETs 116 has failed closed (as described above). In one embodiment of the present invention, the MCU 102 is further programmed to determine that one or more of the power FETs 116 has failed (or may be failing) by determining whether there is an imbalance in V across one power FET compared to the other power FETs. Under normal operating conditions, the RMS value of the line voltage should be substantially the same, so at any given time, the RMS value of V across all three power FETs 116 should also be substantially the same. Any significant imbalance in V among the three phases provides an indication that one or more of the power FETs 116 has failed or possibly is failing. 17 is a flowchart highlighting a method 1700 performed by the MCU 102 to detect such an imbalance and the steps taken when it is determined that an imbalance in Vdrop exists. First, with all power FETs 116 on, in steps 1702 and 1704, the line-in and line-out current / voltage sensors sense / measure and report the line-in and line-out voltages present at the input and output of the FET power module 106 for all three power FETs 116. Then, using the sensed / measured voltages, in step 1706, the MCU 102 calculates Vdrop across each power FET 116. In decision 1708, if the value of Vdrop is the same for all three power FETs 116 (“NO” at decision 1708), the method 1700 returns to step 1702.However, if the MCU 102 determines that there is a significant imbalance in Vdrop at one power FET 116 compared to the other power FETs 116 (“YES” at decision 1708), the MCU 102 may conclude that one or more of the power FETs 116 has failed or may be failing. Accordingly, at step 1710, the MCU 102 instructs the sense and drive circuit 104 to switch the power FETs 116 off and commands the air gap disconnection unit 108 to create an air gap between the line-in terminal 110 and the line-out terminal 112. Then, at step 1712, the MCU 102 reports to a system monitor that one or more of the power FETs 116 has failed or may be failing and / or instructs the electronic display 113 of the SSCB 100 to indicate that one or more of the power FETs 116 has failed or may be failing.

[0032] In this method 1700 described with reference to FIG. 17, the MCU 102 is programmed to determine that one or more of the power FETs 116 has failed (or may have failed) when it determines that there is a Vdrop imbalance among the three power FETs 116. In a single-phase version of the SSCB 100 in which only a single power FET is used, the MCU 102 is programmed to calculate Vdrop (again from real-time line-in and line-out voltage measurements, but across the single power FET) and determine whether the single power FET has failed based on Vdrop. This method 1800 is illustrated in the flowchart presented in FIG. 18. First, in steps 1802 and 1804, current / voltage sensors on both the line-in and line-out sides of the power FETs 116 sense / measure and report to the MCU 102. Then, in step 1806, the MCU 102 calculates Vdrop across the single power FET 116 and, in decision 1808, determines whether Vdrop>Vds(expected) based on the measured current through the single power FET 116 and the known operating characteristics of the power FET (e.g., obtained from the characteristics of the power FET during the design of the SSCB 100 and / or from operating characteristics provided by the power FET manufacturer). If Vdrop is close to Vds(expected), method 1800 returns to step 1802. However, if the MCU 102 determines in decision 1708 that Vdrop is significantly different from Vds(expected), the MCU 102 can appropriately conclude that the single power FET 116 has failed or may be failing. Thus, in step 1810, the MCU 102 instructs the sense and drive circuit 104 to switch off the power FET 116 and / or commands the air gap disconnection unit 108 to disengage it to form an air gap between the line in and line out terminals.Finally, in step 1812, the MCU 102 alerts a system supervisor that the power FET 116 has failed or may be failing so that an electrician or engineer can then be dispatched to the site to either replace the SSCB 100 with a new SSCB or remove the defective power module 106 and replace it with a new power module 106 having a properly functioning power FET 116. Additionally (or alternatively), the MCU 102 can instruct an electronic display on the SSCB 100 to indicate that the power FET 116 has failed or may be failing.

[0033] In a preferred embodiment of the SSCB 100, the lineout current / voltage sensor 156 includes a Hall effect sensor that generates a Hall voltage proportional to the magnetic field formed around each of the lineout conductors due to the current flowing through the conductor. Because the strength of the magnetic field is directly proportional to the magnitude of the current flowing through the lineout conductors, the Hall voltage represents the magnitude of the current flowing through the SSCB 100 when the power FET 116 is switched on and the air gap disconnection unit 108 is engaged (the air gap contact switch 114 is closed). Because accurate Hall effect measurements are essential to the proper operation of the SSCB 100, in one embodiment of the present invention, the MCU 102 is programmed to monitor performance and diagnose any current sensing faults. An exemplary method 1900 performed by the SSCB 100 and MCU 102 in this regard is shown in FIG. 19. First, with all power FETs 116 on and the air gap disconnection unit 108 engaged, in step 1902, a Hall effect sensor in the line-out current / voltage sensor 156 senses / measures the line current flowing out of the line-out terminal 112. Preferably, the Hall effect measurement (Hall voltage) is performed in real time, amplified if necessary, and reported to the MCU 102. In decision 1904, the MCU 102 determines, based on the Hall voltage, whether the RMS of any one of the three sensed / measured currents is significantly different from the other two. If “YES,” the MCU 102 can conclude that one of the Hall effect sensors has failed or is failing, and therefore, in step 1906, instructs the sensing and drive circuit 104 to switch off the power FETs 116 and / or generates a solenoid trigger signal for the air gap disconnection unit 108 to trigger the air gap disconnection unit 108 to disengage and form an air gap between the line-in terminal 110 and the line-out terminal 112. Then, in step 1908, the MCU 102 reports the current sensor failure to a system supervisor and / or causes the electronic display 113 of the SSCB 100 to indicate that one or more of the current sensors has failed or may be failing.If, at decision 1904, the MCU 102 determines that the three sensed / measured currents are balanced (all three sensed / measured currents are substantially the same) (“NO” at decision 1904), that determination does not completely rule out the possibility that one or more of the line-in and / or line-out current / voltage sensors 154 and 156 may have failed or possibly failed, so steps 1910 through 1914 and decision 1916 are performed. Specifically, at steps 1910 and 1912, the line-in and line-out voltages are measured for all three phases at the input and output of the FET power module 106. Then, at step 1914, the MCU 102 calculates Vdrop=V(line-in)−V(line-out) for all three phases. Finally, at decision 1916, if the MCU 102 determines that, for any given phase, both V (line in) and V (line out) are high while current is low and Vdrop is higher than expected (“YES” at decision 1916), the MCU 102 may conclude that one or more of the line in and / or line out current / voltage sensors 154 and 156 has failed or may be failing, and steps 1906 and 1908 are performed. Otherwise (“NO” at decision 1916), the method returns to step 1902.

[0034] The exemplary embodiment of the SSCB 100 described herein includes a reset button 144 that a person can press to manually re-engage the air gap disconnection unit 108 and close the air gap between the line-in terminal 110 and the line-out terminal 112. After the reset button 144 is pressed and the air gap contact switches 114 are closed, a person can then press the green ON button 107 to switch on the power FET 116, thereby placing the SSCB 100 in a fully ON state. If, for any reason, pressing the reset button 144 does not successfully re-engage the air gap disconnection unit 108 and a person then presses the ON button 107 to switch on the power FET 116, undesirable arcing may occur across one or more of the air gap disconnection switches 114 when the mechanism is released. To avoid this problem, in one embodiment of the present invention, the MCU 102 and other cooperating components of the SSCB 100 are configured to execute an air gap engagement verification method 2000, an exemplary embodiment of which is shown in FIG. 20 . This air gap engagement verification method 2000 operates on the fact that whenever a person presses the reset button 144 to engage the air gap disconnection unit 108, the movement of the solenoid's plunger 128 generates a small electrical pulse in the coil of the solenoid 118 as the plunger 128 is pushed out of the solenoid's housing to latch and re-engage the air gap disconnection unit 108. The presence and shape of this pulse is used by the MCU 102 in the air gap engagement verification method 2000 to verify that the air gap disconnection unit 108 has actually been properly engaged. Specifically, in step 2002, when the reset button 144 is pressed, the pulse appearing at the terminals of the coil of the solenoid 118 is amplified, filtered, and directed to an input of the MCU 102. The received pulse is then compared by the MCU 102 to an expected pulse in decision 2004.If the received pulse matches the expected pulse ("YES" at decision 2004), the MCU 102 can conclude that the air gap disconnection unit 108 has properly engaged, and as a result, allows the ON button 107 to be pressed to switch on the power FET 116. On the other hand, if the received pulse does not match the expected pulse (or if no pulse is received by the MCU 102 when the reset button 144 is pressed) ("NO" at decision 2004), then in step 2008 the MCU 102 prevents any pressing of the ON button 107 to switch on the power FET 116. In this way, arcing is prevented from occurring across the air gap contact switch 114 when the power FET 116 could otherwise be switched on. Finally, in step 2010, the MCU 102 reports to a system monitor that the air gap disconnection unit 108 may have opened and failed, and / or instructs the electronic display 113 of the SSCB 100 to indicate that the air gap disconnection unit 108 may have opened and failed.

[0035] In one embodiment of the present invention, each of the three phases of the SSCB 100 includes a pair of back-to-back power FETs 116, rather than just a single power FET, as shown in FIG. 21. A back-to-back power FET configuration, similar to that mentioned above and described in commonly assigned U.S. Pat. No. 10,541,530, is desirable in some applications because it facilitates, among other attributes, soft starting of an inductive motor load. During an instantaneous trip condition (e.g., when one or more of the line currents exceed the rated current I of the SSCB 100), RATED some multiple of (for example, I RATEDWhen the voltage across the back-to-back power FETs 116 exceeds 1 / 6 of the threshold voltage (exceeding 1 / 6 of the threshold voltage), the sense and drive circuit 104 switches the power FETs 116 off. When the power FETs 116 are switched off in this situation, high voltage ringing can occur across the SSCB 100, specifically across the drain-to-drain of one or more of the back-to-back power FETs 116. In the version of the FET power module 106 shown in FIG. 21 , a surge protection device (SPD) 2102, e.g., a metal oxide varistor (MOV) or transient voltage suppression (TVS) diode, is connected across each pair of back-to-back power FETs 116 in each phase. The SPD 2102 turns on during an instantaneous trip condition if the voltage developed across the SPD 2102 exceeds a predetermined threshold. When turned on, the SPD 2102 clamps the voltage across the drain-to-drain of each back-to-back power FET configuration to prevent high voltage ringing. However, the SPDs 2102 can only withstand so many such high-voltage suppressions before they begin to degrade and ultimately fail. In one embodiment of the present invention, the MCU 102 is configured to perform a method 2200 for monitoring the health of the SPDs 2102 and to shut down the SSCB 100 if one or more of the SPDs 2102 fail or degrade sufficiently so that an electrician or engineer can then be dispatched to the site to service the SSCB 100 (e.g., by replacing one or more failed or degraded SPDs 2102) or replace the SSCB 100 with a new SSCB 100 having new SPDs 2102. FIG. 22 is a flowchart illustrating an exemplary embodiment of this SPD health monitoring method 2200. First, in step 2202, the MCU 102 constantly monitors the line-in and line-out voltages at the input and output of the SSCB 100. Next, upon determining at decision 2204 that an instantaneous trip condition has occurred (“YES” at decision 2204 ), the sense and drive circuit 104 switches off the power FET 116 at step 2206 .Once the power FETs 116 are switched off, in decision 2208, the MCU 102 determines whether the voltage drop Vdrop across any pair of back-to-back power FETs 116, i.e., the voltage drop Vdrop across any SPD 2102 (based on voltage measurements taken by the line-in and line-out current / voltage sensors 154 and 156), is less than some predetermined minimum voltage threshold (in one exemplary embodiment, less than 60% of the nominal voltage drop of the SPD). (Note that because each SPD 2102 is connected drain-to-drain of its associated back-to-back power FET 116, Vdrop across each pair of back-to-back power FETs 116 is the same as the voltage dropped across its associated SPD 2102.) In one embodiment of the present invention, Vdrop for each phase is the average voltage drop Vdrop(average) determined based on a series of instantaneous voltage drop measurements taken during the instantaneous trip condition event. For each phase, an absolute instantaneous voltage drop measurement is taken during each execution cycle of the MCU 102, and the MCU 102 looks for a plateau by checking the instantaneous value against the previous value. To determine the average voltage drop Vdrop(average) for each pair of back-to-back power FETs 116, the absolute instantaneous voltage drop measurement within the plateau region is added to an accumulator for a given voltage level. This loop also counts the time period of the plateau. Then, using the counted time period and the accumulator value, the average voltage drop Vdrop(average) is calculated for a defined current. This is repeated for all three phases, resulting in the average clamp voltage levels and time periods of the plateau region for the three phases. Due to the nature of a three-phase system, two of the SPDs 2102 are affected in a similar manner during an instantaneous trip condition event. When decision 2208 is being performed, the two affected phases are identified by measuring the current, and once identified, the MCU 102 determines whether Vdrop(average) for either of the two identified phases has fallen below a predetermined minimum voltage threshold.If the MCU 102 determines in decision 2208 that all of the SPDs 2102 are still operating as intended (i.e., “NO” in decision 2208), then in step 2210 the MCU 102 causes the air gap disconnection unit 108 to disengage and form an air gap between the line-in terminal 110 and the line-out terminal 112, thereby generating a solenoid trigger signal to respond to the instantaneous trip condition previously detected in decision 2204. On the other hand, if the MCU 102 determines in decision 2208 that Vdrop(average) in any of the three phases has fallen to a level below a predetermined minimum voltage threshold (i.e., “YES” in decision 2208), the MCU 102 can appropriately conclude that one or more of the SPDs 2102 may have failed or have degraded sufficiently (due to suppressing too many voltage surges) that they should be replaced. Thus, if a "YES" at decision 2208 results, in step 2212, the MCU 102 generates a solenoid trigger signal to disengage the air gap disconnection unit 108 and create an air gap between the line-in terminal 110 and the line-out terminal 112. Finally, in step 2214, the MCU 102 alerts a system monitor that one or more of the SPDs 2102 in the SSCB 100 have deteriorated sufficiently to the point that they may have failed or need to be replaced, and / or causes the electronic display 113 of the SSCB 100 to indicate that one or more of the SPDs 2102 have deteriorated sufficiently to the point that they may have failed or need to be replaced.

[0036] As explained in detail above, it is preferable to first turn off the power FETs 116 in the FET power module 106 before forming the air gap to prevent arcing across the air gap. To facilitate this operation, in one embodiment of the present invention, the release button 122 (see FIGS. 1-3 and 5) includes a microswitch that opens and closes in response to the physical displacement of the release button 122. (In a preferred embodiment of the SSCB 100, two tactile mechanical switches 115 (see FIG. 3) are used (two for redundancy).) The microswitch is in electrical communication with the MCU 102, allowing the MCU 102 to monitor its state, i.e., whether it is open or closed. As long as the release button 122 is in its natural state (not pressed), the microswitch remains closed. However, if a person presses the release button 122 and the release button moves into the SSCB housing, the microswitch opens. When the MCU 102 detects this change in the state of the microswitch, it immediately responds by instructing the sense and drive circuit 104 to switch off the power FET 116 in the FET power module 106. The power FET 116 is switched off very quickly in this process, well before the air gap disconnection unit 108 can complete forming the air gap. In this way, arcing across the air gap is prevented.

[0037] In one embodiment of the present invention, the computer program instructions stored within CRM 103 and retrieved and executed by MCU 102 not only enable MCU 102 to monitor the operational status of one or more microswitches 115, but they also include instructions that enable MCU 102 to determine whether one or more microswitches 115 have failed, respond to any determined failure by, for example, shutting down SSCB 100, and notify a system monitor of any failure. Figure 23 is a flowchart illustrating a method 2300 performed by MCU 102 according to this particular aspect of the present invention. First, immediately after the voltage at the input of SSCB 100 collapses but the power at the DC power of the internal power supply does not collapse (step 2302), MCU 102 determines, in decision 2304, whether it has received a change in the status signal from one or more microswitches 115 indicating that a person has pressed release button 122. If decision 2304 is "YES," the MCU 102 can properly conclude in step 2306 that the release button 122 was actually pressed and enter a fault state in step 2308 (the power FET 116 is switched off and the air gap disconnection unit 108 is disengaged). On the other hand, if the MCU 102 does not receive a signal from one or more microswitches 115 ("NO" at decision 2304), it remains possible that a person pressed the release button 122 but that for some reason the MCU 102 did not receive a signal indicating that the release button 122 was pressed. Decision 2310 is performed to determine whether the release button 122 was actually pressed but one or more microswitches 115 may have failed. Specifically, in decision 2310, the MCU 102 inquires as to whether the SSCB 100 initiated a command to trigger the air gap disconnection unit 108 (automatically by triggering the solenoid 118) when the line-in voltage sensor 154 detected a voltage collapse at the SSCB input.If so (“YES” at decision 2310), then in step 2312, the MCU 102 concludes that the SSCB 100 automatically responded to the fault (without a human pressing the release button 122) and commands the SSCB 100 to enter a fault state (the power FET 116 is switched off and the air gap disconnection unit 108 is disengaged) in step 2314. On the other hand, if the MCU 102 did not receive a state change signal from one or more microswitches 115 (“NO” at decision 2304) and the MCU 102 did not initiate a command to trigger the air gap disconnection unit 108 (“NO” at decision 2310), then in step 2316, the MCU 102 concludes that a human did in fact press the release button 122, but that for some reason, the MCU 102 did not receive a signal from one or more microswitches 115 when the release button 122 was pressed. In other words, in step 2216, the MCU 102 can properly conclude that a person did in fact press the release button 122, but that one or more of the microswitches 115 may have failed. After making this determination, in step 2318, the MCU 102 instructs the sense and drive circuit 104 to switch off the power FET 116, trigger the air gap disconnection unit 108 to disengage, and indicate on the SSCB 100's electronic display 113 that one or more of the microswitches 115 may have failed. Finally, in step 2320, the MCU 102 reports to a system monitor (via the communication / control bus 124) that one or more of the microswitches 115 may have failed and need to be replaced.

[0038] In the exemplary embodiments of the invention described above, the SSCB 100 is designed to be capable of performing various diagnostic, maintenance, and self-protection methods without any human intervention. In some embodiments of the invention, the SSCB 100 is designed so that many of the various methods described above can also (or alternatively) be performed on-demand, i.e., initiated by a user, for example, an electrician, engineer, or electric utility. To facilitate this on-demand capability when the SSCB 100 is installed in a distribution board 2402 (see FIG. 24), the SSCB 100, and particularly its MCU 102, is programmed to communicate with an external user computer 2406 via a wired (or wireless) head-end interface 2404 configured in the distribution board 2402. FIG. 25 is a diagram illustrating the major components of the user computer 2406, which may comprise a server, desktop computer, laptop computer, tablet computer, smartphone, or any other type of computing device. As shown in the drawing ( FIG. 25 ), the user computer 2406 includes a microprocessor 2502, a CRM 2504, a human-machine interface (HMI) 2506 through which a user can interact with the user computer 2406, an electronic display 2508, and an optional mass storage device 2510 (e.g., a magnetic hard drive or solid-state drive). The CRM 2504 is configured to store computer program instructions that direct how the microprocessor 2502 operates. These computer program instructions include instructions and protocols that provide the microprocessor 2502 with the ability to communicate with the MCUs 102 in the various SSCBs 100 via the head-end interface 2404 over the communication / control bus 124, instructions that allow the microprocessor 2502 to individually address each of the SSCBs 100, and instructions that control when the microprocessor 2502 communicates with the MCUs 102 in the various SSCBs 100.In one embodiment of the present invention, the user interaction capabilities provided by user computer 2406 are presented in the form of a user-interactive graphical user interface (GUI), and computer program instructions stored within CRM 2504 of user computer 2406 include instructions that direct microprocessor 2502 to generate and display one or more GUI windows or pages on the user computer's electronic display 2508. Preferably, electronic display 2508 is equipped with touchscreen technology that allows a user of user computer 2406 to interact with the GUI windows or pages by touching the screen of electronic display 2508 or by using a stylus. Using simple or multi-touch gestures using one or more fingers, a user can scroll, zoom, input information, etc., and control the GUI windows or pages and content displayed on electronic display 2508. The GUI and electronic display 2508 may alternatively (or additionally) be configured to allow a user to interact with the GUI windows or pages and content using a mouse, touchpad, or other non-touchscreen input device. To facilitate user interactivity, the GUI window or page preferably includes icons and widgets such as radio buttons, sliders, spinners, drop-down lists, menus, combo and text boxes, scroll bars, etc. The computer program instructions executed by the microprocessor 2502 to generate the GUI preferably include an app hosted on the local gateway, but may alternatively include a web service installed on a local server or remotely (e.g., in the cloud). Preferably, the GUI includes a calendar that allows the user to schedule periodic occurrences of diagnostics and / or maintenance, and user-interactive icons and / or widgets that allow the user to initiate on-demand diagnostics and / or maintenance.Whether scheduled or on-demand, the microprocessor 202 of the user computer 2406 is preferably programmed to report a GUI window or page displaying the results of any diagnostic and / or maintenance execution, any failures (or predicted failures) and recommended corrective actions of any of the various components of any given SSCB 100. To further facilitate on-demand diagnostics and / or maintenance, in one embodiment of the present invention, the SSCB 100 further includes an on-demand diagnostic button (e.g., labeled "Test"), or alternatively, the standby button 111 is configured to function as a dual-purpose button that, when pressed, initiates an on-demand diagnostic and / or maintenance process.

[0039] While various embodiments of the present invention have been described, they have been presented by way of example, and not limitation. It will be apparent to those skilled in the art that various changes in form and detail can be made to the illustrative embodiments without departing from the true spirit and scope of the invention. Therefore, the scope of the present invention should not be limited by the details of the illustrative embodiments, but should instead be determined by the appended claims, including the full range of equivalents to which such claims are entitled. [Explanation of symbols]

[0040] 100 Solid State Circuit Breaker (SSCB) 102 Microcontroller Unit (MCU) 103 CRM, Computer Readable Memory (CRM) 104 Sensing and driving circuit, sensing and driving circuit board, air gap contact switch 105 Control board 106 Field Effect Transistor (FET) Power Module, Power FET 107 On button, On (green) button 108 Air Gap Cutting Unit 109 Off button, Standby button 110 Line-in terminal 111 Standby button, off red button 112 Line out terminal 113 Electronic Display 114 Air gap contact switch, air gap disconnect switch 115 Microswitch 116 Power FET 117 Air Gap Disconnect Capacitor 118 Solenoid, Primary Solenoid, Air Gap Disconnecting Unit Solenoid 119 ribbon cable 120 Switch 122 release button 123 Cap Bypass Switch 124 Communication and Control (Communication / Control) Bus 126 AC / DC converter, AC / DC power converter 128 Plunger 130 Latch, Rotating Latch 132 Upper lip 136 Holster 138 Cutting spring 140 Connecting member 142 Cam surface 144 Reset Button 146 Lockout-Tagout (LOTO) Hole 150 Communication and Control (Communication / Control) Bus Shield 152 Positive Temperature Coefficient (PTC) Thermistor 154 Current and Voltage Sensor, Line-in Current / Voltage Sensor, Voltage Sensor, Line-in Voltage Sensor 156 Current and Voltage Sensors, Voltage Sensors, Line-out Current / Voltage Sensors, Line-out Voltage Sensors 160 Lockout mechanisms, secondary lockout mechanisms, mechanical lockout mechanisms 1202 External "Watchdog", Watchdog 2102 Surge Protection Device (SPD) 2402 Distribution board 2404 Headend Interface 2406 External User Computers 2502 microprocessor 2504 CRM 2506 Human Machine Interface (HMI) 2508 Electronic Display 2510 Mass Storage Device

Claims

1. a line-in terminal and a line-out terminal; a power semiconductor device arranged between the line-in terminal and the line-out terminal; a sense and drive circuit for monitoring current through said power semiconductor device and for switching off said power semiconductor device upon detecting a short circuit or an overload of unacceptably long duration; a microcontroller unit (MCU) configured to monitor the operability of the power semiconductor device when the power semiconductor device is on during normal operating conditions, and to generate an alert indicating that the power semiconductor device has failed or is likely to have failed upon determining that the power semiconductor device has failed or is likely to have failed; Solid-state circuit breaker (SSCB).

2. 2. The SSCB of claim 1, further comprising an air gap disconnection unit connected in series with the power semiconductor device between the line-in terminal and the line-out terminal, the air gap disconnection unit configured to form an air gap between the line-in terminal and the line-out terminal after the sensing and drive circuitry switches the power semiconductor device off, wherein during a normal operating condition, when the power semiconductor device is on and no air gap is formed between the line-in terminal and the line-out terminal, the MCU is further configured to monitor the operability of the air gap disconnection unit and, upon determining that the air gap disconnection unit has failed or is likely to have failed, instruct the sensing and drive circuitry to switch the power semiconductor device off.

3. 3. The SSCB of claim 2, wherein the MCU is operable to determine whether the air gap disconnection unit has failed open or is likely to have failed open, and is also operable to determine whether the air gap disconnection unit has failed closed or is likely to have failed closed.

4. 4. The SSCB of claim 3, wherein the MCU is configured to instruct the sensing and drive circuitry to switch the power semiconductor device off and prevent the power semiconductor device from being switched on when the MCU determines that the air gap disconnection unit has failed.

5. 3. The SSCB of claim 2, further comprising a reset button that a person can press to re-engage the air gap disconnection unit and close the air gap after the SSCB trips, and wherein the MCU is configured to verify that the air gap disconnection unit has successfully re-engaged in response to the reset button being pressed before allowing the sensing and drive circuitry to switch on the power semiconductor device.

6. 6. The SSCB of claim 5, wherein the reset button includes a lock-out-tag-out (LOTO) hole into which a padlock or other locking device may be inserted to lock the reset button and prevent the reset button from being depressed to re-engage the air gap disconnection unit.

7. 7. The SSCB of claim 6, further comprising: a secondary lockout mechanism that is triggered by the MCU when the MCU determines that one or more of the SSCB's primary components or primary functions have failed, may have failed, or may be failing, and that, when triggered, prevents the reset button from being depressed to re-engage the air gap disconnection unit, regardless of whether the padlock or other locking device is inserted through the LOTO hole.

8. 3. The SSCB of claim 2, further comprising: a line-in current / voltage sensor configured between the air gap disconnection unit and a power semiconductor device; and a line-out current / voltage sensor coupled to the line-out terminal; and wherein the MCU is further configured to monitor operability of the line-in current / voltage sensor and the line-out current / voltage sensor, and, upon determining that the line-in current / voltage sensor has failed or is likely to fail, or upon determining that the line-out current / voltage sensor has failed or is likely to fail, instruct the sensing and drive circuitry to switch off the power semiconductor device and / or trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

9. 3. The SSCB of claim 2, wherein the MCU is configured to determine whether the power semiconductor device has failed closed or is likely to have failed closed, and, when determining that the power semiconductor device has failed closed or is likely to have failed closed, trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

10. 3. The SSCB of claim 2, wherein the MCU is further configured to trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal when a short circuit or an overload of unacceptably long duration occurs, regardless of whether the sensing and drive circuitry successfully switched off the power semiconductor device.

11. 10. The SSCB of claim 1, further comprising an electronic display configured to alert a person when the power semiconductor device has failed or may have failed.

12. 3. The SSCB of claim 2, further comprising an electronic display configured to alert a person when the air gap disconnection unit has failed or may have failed.

13. 10. The SSCB of claim 1, wherein the SSCB further comprises a direct current (DC) power supply configured to provide DC power to the MCU and other DC components of the SSCB, and wherein the MCU is configured to monitor an output voltage of the DC power supply and to instruct the sensing and drive circuitry to switch off the power semiconductor device when the MCU determines that the output voltage has dropped below a predetermined threshold voltage.

14. 3. The SSCB of claim 2, wherein the SSCB further comprises a direct current (DC) power supply configured to provide DC power to the MCU and other DC components of the SSCB, and wherein the MCU is configured to monitor an output voltage of the DC power supply and to instruct the sensing and drive circuitry to switch off the power semiconductor device when the MCU determines that the output voltage has dropped below a predetermined threshold voltage.

15. 15. The SSCB of claim 14, wherein the MCU is further configured to trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal when the MCU determines that the output voltage of the DC power supply has dropped below the predetermined threshold voltage.

16. 16. The SSCB of claim 15, wherein the air gap disconnection unit comprises a solenoid that triggers the air gap disconnection unit and an air gap disconnection capacitor that provides current to operate the solenoid, and wherein the MCU is configured to monitor operability of the air gap disconnection capacitor and, upon determining that the air gap disconnection capacitor has failed or is likely to fail, enable a bypass circuit that bypasses the air gap disconnection capacitor and temporarily configures the DC power supply to provide current to operate the solenoid instead of the air gap disconnection capacitor.

17. 16. The SSCB of claim 15, wherein the air gap disconnection unit comprises an air gap disconnection capacitor, and wherein the air gap disconnection capacitor is configured to temporarily function as a power source for the MCU in place of the DC power source when the MCU determines that the output voltage of the DC power source has dropped below the predetermined threshold voltage.

18. 10. The SSCB of claim 1, wherein the SSCB further comprises a thermistor proximate to the power semiconductor device, and wherein the MCU is further configured to monitor the thermistor and, upon detecting a possible thermal runaway condition in the power semiconductor device, instruct the sense and drive circuitry to switch off the power semiconductor device.

19. 10. The SSCB of claim 1, further comprising: a watchdog circuit external to the MCU configured to monitor the operability of the MCU and to switch off the power semiconductor device or to instruct the sensing and drive circuitry to switch off the power semiconductor device when the watchdog circuit determines that the MCU has failed or is likely to fail.

20. 20. The SSCB of claim 19, further comprising an air gap disconnection unit connected in series with the power semiconductor device between the line-in terminal and the line-out terminal, and further configured to trigger the air gap disconnection unit to form an air gap between the line-in terminal and the line-out terminal when the watchdog circuit determines that the MCU has failed or is likely to fail.

21. 3. The SSCB of claim 2, further comprising a surge protection device (SPD) configured to prevent the power semiconductor device from being exposed to an excessively high voltage, and wherein the MCU is configured to monitor the operability of the SPD and, when the MCU determines that the SPD has failed or has sufficiently deteriorated beyond its expected predetermined lifespan, trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

22. 3. The SSCB of claim 2, further comprising a release button in mechanical communication with the air gap disconnection unit, the release button, when depressed by a person, manually disengaging the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

23. 23. The SSCB of claim 22, wherein the release button comprises a microswitch that opens and closes in response to physical displacement of the release button, and wherein the MCU is configured to monitor the operability of the microswitch and, upon determining that the microswitch has failed or is likely to fail, instruct the sensing and drive circuitry to switch off the power semiconductor device and / or instruct the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

24. The SSCB of claim 1 , wherein the MCU is further configured to generate and provide operational status and diagnostic information regarding the SSCB.

25. 25. The SSCB of claim 24, wherein the MCU is configured to generate and provide the operational status and diagnostic information automatically, alternatively on-demand or according to a predetermined schedule.

26. 25. The SSCB of claim 24, further comprising a communications / control bus connector configured to connect to a communications and control (communications / control) bus over which the MCU can transmit the operating status and diagnostic information to a local or remotely located computer.

27. 25. The SSCB of claim 24, wherein the SSCB further comprises an electronic display configured to display the operating status and diagnostic information.

28. a line-in terminal and a line-out terminal; a power semiconductor device arranged between the line-in terminal and the line-out terminal; an air gap disconnection unit connected in series with the power semiconductor device between the line-in terminal and the line-out terminal; a microcontroller unit (MCU) configured to monitor the operability of the power semiconductor device when the power semiconductor device is on during a normal operating state, and to trigger the air gap disconnection unit to form an air gap between the line-in terminal and the line-out terminal when it determines that the power semiconductor device has failed or is likely to have failed; Solid-state circuit breaker (SSCB).

29. 30. The SSCB of claim 28, wherein the MCU is operable to determine whether the air gap disconnection unit has failed open or is likely to have failed open, and is also operable to determine whether the air gap disconnection unit has failed closed or is likely to have failed closed.

30. 30. The SSCB of claim 29, wherein the SSCB further comprises a sense and drive circuit, and wherein the MCU is configured to instruct the sense and drive circuit to switch the power semiconductor device off and prevent the power semiconductor device from being switched on when the MCU determines that the air gap disconnection unit has failed closed.

31. 29. The SSCB of claim 28, wherein the SSCB further comprises a reset button that a person can press to reengage the air gap disconnection unit and close the air gap after the SSCB trips, and the MCU is configured to verify that the air gap disconnection unit has successfully reengaged in response to the reset button being pressed before allowing the power semiconductor device to be switched on.

32. 32. The SSCB of claim 31 , wherein the reset button includes a lock-out-tag-out (LOTO) hole into which a padlock or other locking device may be inserted to lock the reset button and prevent the reset button from being depressed to re-engage the air gap disconnection unit.

33. 33. The SSCB of claim 32, further comprising: a secondary lockout mechanism that is triggered by the MCU when the MCU determines that one or more of the SSCB's primary components or primary functions have failed, may have failed, or may be failing, and that, when triggered, prevents the reset button from being depressed to re-engage the air gap disconnection unit, regardless of whether the padlock or other locking device is inserted through the LOTO hole.

34. 29. The SSCB of claim 28, wherein the SSCB further comprises sensing and drive circuitry, a line-in current / voltage sensor configured between the air gap disconnection unit and the power semiconductor device, and a line-out current / voltage sensor coupled to the line-out terminal, wherein the MCU is further configured to monitor operability of the line-in current / voltage sensor and the line-out current / voltage sensor, and, upon determining that the line-in current / voltage sensor has failed or is likely to fail, or upon determining that the line-out current / voltage sensor has failed or is likely to fail, instruct the sensing and drive circuitry to switch off the power semiconductor device and / or trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

35. 29. The SSCB of claim 28, wherein the SSCB further comprises sensing and drive circuitry and a direct current (DC) power supply configured to supply DC power to the MCU and other DC components of the SSCB, wherein the MCU is configured to monitor an output voltage of the DC power supply and, when the MCU determines that the output voltage has dropped below a predetermined threshold voltage, instruct the sensing and drive circuitry to switch off the power semiconductor device and / or trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

36. 36. The SSCB of claim 35, wherein the air gap disconnection unit comprises a solenoid that triggers the air gap disconnection unit and an air gap disconnection capacitor that provides current to operate the solenoid, and wherein the MCU is configured to monitor the operability of the air gap disconnection capacitor and, upon determining that the air gap disconnection capacitor has failed or is likely to fail, enable a bypass circuit that bypasses the air gap disconnection capacitor and temporarily configures the DC power supply to provide current to operate the solenoid instead of the air gap disconnection capacitor.

37. 36. The SSCB of claim 35, wherein the air gap disconnection unit comprises an air gap disconnection capacitor, and wherein the air gap disconnection capacitor is configured to temporarily function as a power source for the MCU in place of the DC power source when the MCU determines that the output voltage of the DC power source has dropped below the predetermined threshold voltage.

38. 29. The SSCB of claim 28, wherein the SSCB further comprises a thermistor proximate to the power semiconductor device, and wherein the MCU is further configured to monitor the thermistor and, upon detecting a possible thermal runaway condition in the power semiconductor device, instruct sensing and drive circuitry to switch off the power semiconductor device.

39. 29. The SSCB of claim 28, further comprising a watchdog circuit external to the MCU configured to monitor the operability of the MCU and generate a signal to switch off the power semiconductor device upon determining that the MCU has failed or is likely to fail.

40. 40. The SSCB of claim 39, wherein the watchdog circuit is further configured to trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal when the watchdog circuit determines that the MCU has failed or may be failing.

41. 29. The SSCB of claim 28, further comprising a surge protection device (SPD) configured to prevent the power semiconductor device from being exposed to an excessively high voltage, and wherein the MCU is configured to monitor the operability of the SPD and, upon determining that the SPD has failed or has sufficiently deteriorated beyond its expected predetermined lifespan, trigger the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

42. 30. The SSCB of claim 28, further comprising a release button in mechanical communication with the air gap disconnection unit, the release button, when depressed by a person, manually disengaging the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

43. 43. The SSCB of claim 42, wherein the SSCB further comprises sensing and drive circuitry, the release button comprising a microswitch that opens and closes in response to physical displacement of the release button, and the MCU is configured to monitor the operability of the microswitch and, upon determining that the microswitch has failed or is likely to fail, instruct the sensing and drive circuitry to switch off the power semiconductor device and / or instruct the air gap disconnection unit to form the air gap between the line-in terminal and the line-out terminal.

44. 30. The SSCB of claim 28, further comprising an electronic display configured to display information regarding the viability and operating status of the SSCB, including the air gap disconnection unit and the power semiconductor device.

45. 45. The SSCB of claim 44, wherein the electronic display comprises display technology that allows the electronic display to continue to display the information even after power to the electronic display is removed.

46. 30. The SSCB of claim 28, wherein the MCU is further configured to provide operational status and diagnostic information regarding the SSCB.

47. 47. The SSCB of claim 46, wherein the MCU is configured to generate and provide the operational status and diagnostic information automatically, alternatively on-demand or according to a predetermined schedule.

48. 47. The SSCB of claim 46, further comprising a communications / control bus connector configured to connect to a communications and control (communications / control) bus over which the MCU can transmit the operating status and diagnostic information to a local or remotely located computer.

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