System and method for protecting a circuit

Abstract

A system includes a circuit protection device (CPD) having an input coupled to an aircraft power generator and an output coupled to an aircraft electrical load. A shorted switch is coupled to an input of the CPD. The shorting switch, when closed, provides a fault current path back to the aircraft power generator and avoids through the CPD and aircraft electrical loads. The controller selectively opens and closes one or more of the CPD and the shorted switch based on voltage measurements from the one or more voltage sensors and current measurements from the at least one current sensor.

Description

Technical Field

[0001] The present disclosure generally relates to approaches for protecting circuits, such as switching circuits. Background Art

[0002] Switching circuits are used to switch current, voltage, and power within a circuit. For example, these types of circuits are used in aircraft to switch current, voltage, and power between voltage sources and aircraft systems and components. Occasionally, electrical shorts occur within an aircraft, and these can generate voltage or current surges that can damage switches within the switching circuits. To prevent this damage, circuit protection devices can be used. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Various needs are at least partially met by providing methods and apparatus for protecting electrical devices such as switches, particularly when studied in conjunction with the accompanying drawings. A complete and enabling disclosure of aspects of the present disclosure, including the best mode thereof, to one of ordinary skill in the art is set forth in the specification with reference to the accompanying drawings, wherein:

[0004] Figure 1 depicts a circuit diagram of a system including a circuit protection device according to various embodiments of the present disclosure;

[0005] Figure 2 depicts a circuit diagram of a system including a circuit protection device that has been actuated according to various embodiments of the present disclosure;

[0006] Figure 3 depicts a circuit diagram of a system including a circuit protection device according to various embodiments of the present disclosure;

[0007] Figure 4 depicts a circuit diagram of a system including a circuit protection device that has been actuated according to various embodiments of the present disclosure;

[0008] Figure 5 depicts a flow chart of an approach for providing circuit protection according to various embodiments of the present disclosure;

[0009] Figure 6 depicts a waveform diagram showing fault current used in accordance with various embodiments of the present disclosure;

[0010] Figure 7 depicts a flow chart illustrating the operation of a controller according to various embodiments of the present disclosure;

[0011] Figure 8 depicts a system diagram showing how various embodiments according to the present disclosure may be deployed in an aircraft; and

[0012] Figure 9Depicted is a circuit diagram of another circuit protection system according to various embodiments of the present disclosure.

[0013] The elements in the drawings are shown for simplicity and clarity and are not necessarily drawn to scale. For example, the size and / or relative positioning of some elements in the drawings may be exaggerated relative to other elements to help improve understanding of the various embodiments of the present teachings. In addition, common but well-known elements that are useful or necessary in commercially feasible embodiments are generally not depicted to facilitate less obscure understanding of these various embodiments of the present teachings. Certain actions and / or steps may be described or depicted in a particular order of occurrence, and those skilled in the art will understand that such specificity with respect to order is not actually required. DETAILED DESCRIPTION

[0014] The approaches provided herein provide circuit protection devices and structures that prevent damage to sensitive switching devices deployed within power supply systems, sometimes referred to herein as primary switching devices or circuit protection devices (CPDs). In these aspects, and as will be described herein, a shorting switch is used to divert a rupture or fault current away from the primary switching device or CPD during a short circuit event.

[0015] In many power distribution systems, each load is typically protected by a CPD. These can be simple electromechanical circuit breakers, contactors, relays, SSPCs (solid-state power controllers), or microelectromechanical system (MEMS) switches, to name a few. During a fault condition (such as a short circuit), the CPD interrupts the fault current, which can be several orders of magnitude greater than its rated operating current. This operation leads to rapid component wear. A characteristic of these fault events is that the di / dt (change in current over time) can be very high, for example, when the loop inductance is low or when the pre-existing current in the circuit is high. Consequently, when the CPD trips, the current amplitude can reach extremely high peaks and damage the CPD.

[0016] In one example, a CPD (e.g., an electromechanical circuit breaker, contactor, relay, SSPC, or MEMS device or switch) is connected in series to an aircraft electrical load. The CPD protects the aircraft electrical load from a short circuit event. A shorting switch is electrically connected in parallel to the CPD and the aircraft electrical load and provides a path for rupture and short circuit currents to be directed away from the CPD during a short circuit event.

[0017] In another example, a CPD can include a bypass switch (sometimes referred to herein as a hybrid switch or CPD) electrically connected in parallel to the MEMS device. During a short circuit event, the bypass switch diverts a certain amount of current away from the MEMS device. The short circuit switch is used to temporarily divert other amounts of current away from the MEMS device and the bypass switch during the short circuit event. This structure and operation reduces the amount of rupture or short circuit current experienced by the entire CPD (bypass switch and MEMS device) during the short circuit event, and thereby reduces the corresponding voltage drop across the MEMS device when the MEMS device trips open. Because the magnitude of this voltage drop is significantly reduced, the resulting damage or wear to the MEMS device is prevented, reduced, or minimized.

[0018] The main switching element or CPD provides a balance of low on-resistance and high break current capability. In contrast, the short-circuiting switch has a high break current capability and an "on" resistance (together with the resistance of the optional fuse) that is less than or at least equivalent to the resistance of the main switching element or CPD, so as to divert most of the fault current in the event of a short circuit.

[0019] It will be appreciated that a single shorting switch may be provided per CPD or for a group of CPDs. For example, an electronic circuit breaker panel may have a single switch, or a group may have a single switch.

[0020] Advantageously, the approaches provided herein reduce wear on CPDs during short-circuit faults, extending their lifespan. These approaches contribute to the feasibility of novel switchgear that would otherwise struggle to handle extreme short-circuit faults. While a short-circuiting switch can, in some cases, be physically larger and more highly rated than a bypass switch, it allows the bypass switch to have a lower rating, thereby reducing cost. Thus, in systems where one short-circuiting switch serves multiple parallel switches, there can be significant overall savings in both the physical size and cost of the system.

[0021] Additionally, these approaches provide shorting action of the shorting switch (which need only be temporary) that protects the CPD (eg, MEMS device and bypass switch) from excessive transient voltages and / or currents during load switching, surge, and overload / fault conditions.

[0022] A short-circuiting switch can protect multiple switches, allowing the latter to be derated, thereby reducing the weight and size of the entire system. In addition, due to a fault, high short-circuit currents can pass through the short-circuiting switch for a longer period of time, and this can be used to more reliably trigger upstream protective devices.

[0023] As mentioned above, these approaches are particularly advantageous when the CPD is or includes a MEMS device. MEMS devices have very low on-resistance (e.g., 10 milliohms for a 10A-rated device) and are well-suited for carrying current, but cannot switch current without risk of damage unless the voltage across the MEMS device is kept very low during the switching action. In contrast to contactors, which have considerable thermal capacity to withstand arcing at the contacts during switching, MEMS devices cannot and will be damaged by such operation. Therefore, they are used in conjunction with a solid-state switching device (bypass switch) to form a hybrid switch. The voltage drop across the switch and / or the current through the switch during a short circuit can still be sufficient to damage the MEMS device. The present approach provides mitigation by introducing an additional shorting switch that diverts a majority (e.g., approximately 85%) of the fault current away from the MEMS device during a short circuit event, significantly reducing the chance of damage to the MEMS device.

[0024] In many of these embodiments, a system includes a circuit protection device (CPD) having an input coupled to an aircraft power generator and an output coupled to an aircraft electrical load. The system also includes a short-circuiting switch connected to the input of the CPD. When closed, the short-circuiting switch provides a fault current path back to the aircraft power generator and avoids passing through the CPD and the aircraft electrical load. The system also includes a controller coupled to the CPD, the short-circuiting switch, one or more voltage sensors, and a current sensor. The controller is configured to receive voltage measurements from the voltage sensors and current measurements from the current sensors. In one aspect, one voltage sensor is coupled to the input of the CPD, and another voltage sensor is coupled between the input and output of the CPD. The current sensor is coupled to the output of the CPD. Based on the voltage and current measurements, the controller can selectively open and close one or more of the CPD and the short-circuiting switch.

[0025] In one aspect, the CPD includes a bypass switch and a microelectromechanical system (MEMS) device. In other aspects, the CPD includes a metal oxide semiconductor field effect transistor (MOSFET) switch.

[0026] In an example, the aircraft power generator is an aircraft engine, a converter, or a battery. Other examples are possible.

[0027] In other examples, the aircraft electrical load is a pump, a heating element, or power distribution equipment.Other examples are also possible.

[0028] In other embodiments of these embodiments, a system includes a microelectromechanical system (MEMS) device, a bypass switch, a shorting switch, and a controller. The MEMS device has an input coupled to an aircraft power generator and an output coupled to an aircraft electrical load. The bypass switch is electrically connected in parallel with the MEMS device. When closed, the bypass switch provides a first alternative current path around the MEMS device. The shorting switch is connected to the input of the MEMS device and the input of the bypass switch. When closed, the shorting switch provides a second alternative current path that returns to the aircraft power generator and avoids the CPD and the aircraft electrical load. The controller is coupled to the bypass switch, the shorting switch, one or more voltage sensors, the MEMS device, and one or more current sensors. The controller is configured to receive voltage measurements from the voltage sensors and current measurements from the current sensors. In one aspect, one voltage sensor is coupled to the input of the MEMS device, and another voltage sensor is coupled between the input of the CPD and the output of the CPD. The current sensor is coupled to the output of the MEMS device; based on the voltage and current measurements, one or more of the MEMS device, the bypass switch, and the shorting switch are selectively opened and closed.

[0029] In an example, the bypass switch is a MOSFET. In other examples, the shorting switch is an insulated gate bipolar transistor (IGBT).

[0030] In some aspects, the aircraft power generator is a generator that draws power from the aircraft engine via an accessory gearbox, a power converter, or a battery. In other aspects, the aircraft electrical load is a pump, a heating element, or a power distribution device.

[0031] In some examples, the controller also selectively opens and closes the MEMS device. In yet other aspects, the controller compares the measured current to a first threshold and a second threshold in determining whether to open or close the bypass switch and the shorting switch. In still other aspects, the controller compares the measured voltage to various thresholds in determining whether to open or close the bypass switch and the shorting switch.

[0032] In some other examples, the controller compares the measured current to a first threshold and a second threshold in determining whether to open or close the bypass switch and the shorting switch, and wherein the controller compares the measured voltage to various thresholds in determining whether to open or close the bypass switch and the shorting switch.

[0033] In still other examples, the fuse is electrically connected in series with the shorting switch.

[0034] In yet other embodiments of these embodiments, a method is provided in which a bypass switch is electrically connected in parallel with a microelectromechanical system (MEMS) device. The bypass switch provides a first alternative current path around the MEMS device when closed. The MEMS device has an input coupled to an aircraft power generator and an output coupled to an aircraft electrical load; a shorting switch is provided connected to the input of the MEMS device and the input of the bypass switch. The shorting switch provides a second alternative current path when closed, which returns to the aircraft power generator and avoids the CPD and the aircraft electrical load. At a controller, voltage measurements are received from one or more voltage sensors and current measurements are received from current sensors. At the controller, based on the voltage measurements and current measurements, one or more of the MEMS device, the bypass switch, and the shorting switch are selectively opened and closed.

[0035] The terms and expressions used herein have the common technical meanings consistent with such terms and expressions as those described by those skilled in the art, unless a different specific meaning has been set forth herein. Unless otherwise specifically indicated, the word "or" when used herein should be interpreted as having a separate structure rather than a connected structure. The terms "coupled," "fixed," "attached," and the like refer to direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment through one or more intermediate components or features, unless otherwise indicated herein.

[0036] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0037] As used herein, approximating language may be applied throughout the specification and claims to modify any quantitative representation that is capable of variation without resulting in a change in the basic function to which it is related. Thus, a value modified by one or more terms such as "about," "approximately," and "substantially" is not intended to be limited to the precise value specified. In at least some instances, approximating language may correspond to the precision of an instrument used to measure a value, or the precision of a method or machine used to construct or manufacture a component and / or system. For example, approximating language may mean within a 10% margin.

[0038] The foregoing and other benefits will become more apparent upon a thorough review and study of the following detailed description.

[0039] Now refer to Figure 1, describes an example of a circuit protection system 100. System 100 includes or has an aircraft power source 102, a source resistor 104, a circuit protection device (CPD) 113, an upstream resistor 106, an upstream inductor 108, a shorting switch 110, a first voltage sensor 116, a second voltage sensor 117, a current sensor 118, a resistor 120, a downstream resistor 122, a downstream inductor 124, a return resistor 126 and a return inductor 128, an aircraft electrical load 130, and a controller 132.

[0040] Aircraft power source 102 may be an aircraft engine, a battery, or other energy, voltage, current, and / or power source. Aircraft power source 102 may also be a converter, such as a transformer rectifier unit (TRU), an automated TRU, or a DC-DC converter (e.g., to provide battery output regulation or DC bus conversion). Source resistor 104 represents the resistance of the aircraft power source and, in one example, is 3 milliohms.

[0041] CPD 113 includes switches and potentially circuit protection devices that protect system 100 from short circuits. In examples, CPD 113 may be an electromechanical circuit breaker, contactor, relay, SSPC, or MEMS device or switch. CPD 113 protects aircraft electrical loads 130 from short circuit events.

[0042] In another example, the CPD 113 includes a bypass switch (sometimes referred to herein as a hybrid switch) electrically connected in parallel to the MEMS device. During a short circuit event, the bypass switch diverts some current away from the MEMS device. Figure 3 and Figure 4 This particular structure is described in more detail.

[0043] Shorting switch 110 is electrically connected in parallel to CPD 113 and aircraft electrical loads 130 and provides a path for rupture and short-circuit current to flow away from CPD 113 during a short-circuit event. In some aspects, and when shorting switch 110 is accidentally activated or fails to open in a timely manner (within a predetermined time limit), it may cause upstream protection devices to trip, thereby removing power from multiple outputs (e.g., various outputs on a power distribution unit or distribution panel). To this end, an inline fuse is provided in shorting switch 110 to trip in the event of a short-circuit failure of shorting switch 110, isolating the fault to a single output. In other words, the fuse prevents accidental closing of shorting switch 110. When used to protect CPD 113, shorting switch 110 only needs to be active (closed) for a very short period of time, which will not cause the fuse to blow.

[0044] First voltage sensor 116 is any type of voltage sensing device, such as a voltmeter that measures the voltage at the input of CPD 113. Second voltage sensor 117 is any type of voltage sensing device that measures the voltage between the input of CPD 113 and the output of CPD 113. Current sensor 118 is any type of current sensing device that measures the current at the output of CPD 113 through resistor 120. Separate current monitors or sensors may be provided for CPD 113 and any switches or devices in shorting switch 110 to adequately protect them and provide fault detection / isolation in the event of a fault within one of the switches.

[0045] Upstream resistor 106, downstream resistor 122, and return resistor represent resistances in the electrical path of the illustrated circuit. For example, these elements represent the resistance of electrical wiring or aircraft structures when they provide an electrical path. Similarly, upstream inductor 108, downstream inductor 124, and return inductor 128 represent inductances in the electrical path of the illustrated circuit. For example, these elements represent the inductance of electrical wiring or aircraft structures when they provide an electrical path.

[0046] Aircraft electrical loads 130 are indicated in the figure by resistors and represent any type of system or component in the aircraft that is supplied with voltage, current, and / or power from aircraft power source 102 via CPD 113. For example, aircraft electrical loads 130 may be pumps, heaters, power distribution equipment, or any other aircraft element requiring current, voltage, or power. Other examples of components and combinations of components are possible.

[0047] The controller 132 can be any microcontroller, computer, or processor-based device having a processor, memory, and programmable input / output peripherals, which is generally designed to manage the operation of other components and devices. It is also understood that common auxiliary accessory devices are included, including memory, transceivers for communicating with other components and devices, etc. These architectural options are well known and understood in the art and need not be further described here. The controller 132 can be configured to perform one or more steps, actions, and / or functions described herein (e.g., by using a corresponding program stored in memory, as will be well understood by those skilled in the art). The controller 132 may include a memory that includes computer instructions that implement any of the functions described herein.

[0048] The controller 132 is configured to obtain voltage readings from the first voltage sensor 116 and the second voltage sensor 117, and current readings from the current sensor 118, and use one or more of these readings to determine when to actuate the shorting switch 110. In one example, when the voltage and / or current as measured by these devices exceeds a given value, the controller 132 sends a control signal to actuate the shorting switch 110. The control signal may actuate it for a predetermined period of time, or until a specific voltage and / or current reading is sensed by the first voltage sensor 116, the second voltage sensor 117, and / or the current sensor 118.

[0049] Now refer to Figure 2 , describes when the short-circuit switch 110 has been actuated Figure 1 An example of a circuit. Figure 2 The circuit has the Figure 1 The circuits have the same elements as those in the previous embodiment, and their descriptions will not be repeated here.

[0050] like Figure 2 As shown in FIG, a short circuit 129 has occurred. As a result, the controller 132 has actuated the CPD 113 and the shorting switch 110. The actuation may have occurred because the voltage sensed by the first voltage sensor 116, the second voltage sensor 117, and / or the current sensed by the current sensor 118 exceeds a predetermined value.

[0051] Short circuit 129 and the actuation of CPD 113 and shorting switch 110 generate fault currents. More specifically, a first fault current 138 flows through CPD 113 and short circuit 129. A second fault current 140 flows through shorting switch 110. Consequently, a total fault current 142 is generated, which is the sum of first fault current 138 and second fault current 140. In one example, second fault current 140 is 85% of total fault current 142. Because a significant amount of total fault current 142 is diverted away from CPD 113, this reduces wear on CPD 113 and / or reduces the chance that CPD 113 will fail.

[0052] Now refer to Figure 3 , another example of a circuit protection system 100 is described. System 100 includes or has an aircraft power source 102, a source resistor 104, a CPD 113, an aircraft electrical load 130 and a controller 132, an upstream resistor 106, an upstream inductor 108, a shorting switch 110, a first voltage sensor 116, a second voltage sensor 117, a current sensor 118, a resistor 120, a downstream resistor 122, a downstream inductor 124, a return resistor 126, and a return inductor 128. These components have been described with reference to FIG. Figure 1 is described, and that description will not be repeated here.

[0053] CPD 113 includes a microelectromechanical system (MEMS) device 112 and a bypass switch 114. MEMS device 112 can be a single MEMS device or multiple MEMS devices or switches (e.g., configured in an array). MEMS device 112 functions to selectively allow current, voltage, and power to flow to aircraft electrical loads 130 when closed (e.g., during normal operation) and to disconnect current, voltage, and power to aircraft electrical loads 130 when open (due to a fault event such as a short circuit). Bypass switch 114 (along with shorting switch 110) is selectively actuated by controller 132 to divert current away from MEMS device 112 during a short circuit event occurring in system 100, thereby allowing MEMS device 112 to open. Separate current monitors or sensors can be provided for bypass switch 114, MEMS device 112, and shorting switch 110 to adequately protect them and provide fault detection / isolation in the event of a fault within one of the switches.

[0054] As described above, these approaches are particularly advantageous when the CPD is or includes a MEMS device, such as MEMS device 112. MEMS device 112 has a very low on-resistance (e.g., 10 milliohms for a 10A-rated device) and is well-suited for carrying current, but cannot switch current without risk of damage unless the voltage across MEMS device 112 remains very low during the switching action. For example, when MEMS device 112 is open, the voltage drop across CPD 113 during a short circuit may still be sufficient to damage MEMS device 112. Therefore, bypass switch 114 is used to divert some current away from MEMS device 112, and in addition, shorting switch 110 diverts other fault current generated by the short circuit. As will be appreciated, during a short circuit event, a significant portion (e.g., approximately 85%) of the total fault current is directed away from MEMS device 112 by shorting switch 110, significantly reducing the chance of damage to MEMS device 112.

[0055] Now refer to Figure 4 , describes when the shorting switch 110 and the bypass switch 114 have been actuated Figure 3 An example of a circuit. Figure 4 The circuit has Figure 3 The circuits have the same elements as those in the previous embodiment, and their descriptions will not be repeated here.

[0056] like Figure 4 As shown in FIG, a short circuit 129 has occurred. As a result, the controller 132 has actuated the bypass switch 114 and the short circuit switch 110 of the CPD 113. Figure 4The MEMS device 112 is also shown to be open. Actuation of the bypass switch 114 and the shorting switch 110 may have occurred because the voltage sensed by the first voltage sensor 116, the second voltage sensor 117 and / or the current sensed by the current sensor 118 exceeds a predetermined value. Figure 5 and Figure 7 Examples of manners for determining when to open and close the bypass switch 114 and / or the shorting switch 110 are described.

[0057] Short circuit 129 and the actuation of bypass switch 114 and shorting switch 110 direct the fault current through system 100. More specifically, a first fault current 138 flows through bypass switch 114 and across short circuit 129. A second fault current 140 flows through shorting switch 110. Thus, a total fault current 142 is generated, which is the sum of first fault current 138 and second fault current 140. In one example, second fault current 140 is 85% of total fault current 142. Because a significant amount of total fault current 142 is diverted away from MEMS device 112, this reduces wear on MEMS device 112 and / or reduces the chance that MEMS device 112 will fail due to the short circuit event.

[0058] Now refer to Figure 5 , describes an example of a way to operate a CPD. In this example, it is assumed that the reference Figure 3 and Figure 4 The system described is in operation. Initially, the MEMS device is closed and delivering current normally to the aircraft electrical loads. The bypass switch and the shorting switch are open.

[0059] At step 502, a short circuit or other fault condition occurs. In this example, the short circuit occurs in the aircraft electrical system.

[0060] At step 504 , the bypass switch 114 is closed and the shorting switch 110 is closed. Closing of the bypass switch 114 and the shorting switch 110 may occur simultaneously or approximately simultaneously. Current is diverted away from the MEMS device 112 by both the shorting switch 110 and the bypass switch 114 .

[0061] At step 506, the MEMS device 112 is turned on. Due to the current diversion, no high voltage is generated across the MEMS device 112. Therefore, the MEMS device 112 can be turned on.

[0062] At step 508, the bypass switch 114 is opened. This may occur some predetermined time after the MEMS device 112 has been opened, such as approximately 5 microseconds after the MEMS device 112 is opened.

[0063] At step 510, the shorting switch 110 is opened. This may occur some predetermined time after the MEMS device 112 has been opened, such as approximately 6 microseconds after the MEMS device 112 is opened.

[0064] Now refer to Figure 6 , depicts an example waveform showing a first fault current 138 passing across a short circuit 129. This example shows Figure 4 The first fault current 138 in the circuit.

[0065] The first fault current 138 is shown along the y-axis and time 139 is shown along the x-axis. In the absence of the shorting switch 110, the fault current waveform 180 rises to a peak at time T2 (172) and falls back to a nominal value at time (T3) 174.

[0066] In contrast, when shorting switch 110 is present in the circuit, waveform 182 is generated. As a result of the inclusion of shorting switch 110, the current through CPD 113 initially rises, but at time (T1) 170, waveform 182 flattens to a stable or nearly stable value before returning to a nominal value at time (T3) 174. The current through CPD 113 should eventually drop to zero because CPD 113 has opened in response to the fault.

[0067] Now refer to Figure 7 , describes the closing under fault conditions Figure 3 and Figure 4 The bypass switch 114 and the shorting switch 110 are each configured as an example of a method of controlling the bypass switch 114 and the shorting switch 110. In one aspect, the method may be implemented by computer instructions executed by a processing device. Initially, the MEMS device is closed.

[0068] At step 702, a current from the CPD 113 is obtained as measured by the current sensor 118. At step 704, a first voltage at the input of the CPD 113 is obtained as measured by the first voltage sensor 116, and a second voltage between the input and output of the CPD 113 is obtained as measured by the second voltage sensor 117.

[0069] At step 706, a determination is made as to whether the measured first voltage is greater than a first threshold voltage (Vthresh1) and / or whether the second measured voltage is greater than a second threshold voltage (Vthresh2). If the answer is yes, execution continues to step 708. If the answer is no, execution continues to step 710. For example, the threshold values can be determined experimentally.

[0070] At step 708, the bypass switch 114 and / or the shorting switch 110 are actuated. Determining which of the switches 110 and / or 114 to actuate may depend on the levels of the measured voltages, with some voltages requiring only actuation of the bypass switch and other voltages requiring actuation of both switches 110 and / or 114. Execution then ends.

[0071] At step 710 , a determination is made as to whether the measured current is greater than a first threshold current (I thresh1 ). If the answer is yes, execution continues to step 714 . If the answer is no, execution continues to step 712 .

[0072] At step 714, the bypass switch 114 is actuated (closed). Next, at step 716, a determination is made as to whether the measured current is greater than a second threshold current (Ithresh2). Ithresh2 is greater than Ithresh1. If the answer at step 716 is yes, execution continues at step 720. If the answer at step 716 is no, execution continues at step 718.

[0073] At step 718, the shorting switch 110 remains in the non-actuated (open) state. Execution then ends.

[0074] At step 720, the shorting switch 110 is actuated (closed). Execution then ends.

[0075] At step 712, the state of the switches remains the same. In other words, neither the bypass switch 114 nor the shorting switch 110 is actuated. Execution then ends.

[0076] Now refer to Figure 8 , an example of a circuit protection system 100 is described. Figure 8 An example is Figure 1 、 Figure 2 、 Figure 3 and Figure 4 The aircraft 101 includes an aircraft power source 102, a CPD 113, a controller 132, and an aircraft electrical load 130. These components have been previously described and their description will not be repeated here. Figure 1 、 Figure 2 、 Figure 3 and Figure 4 Other elements shown in FIG.

[0077] Aircraft 101 may be any type of aircraft, such as a jet aircraft, a helicopter, etc. Aircraft 101 may include an aircraft frame, wings, engines, and other aircraft systems. Aircraft power source 102 may be a generator powered by one of the engines, or in other examples, may be a battery. Other examples of power sources are also possible.

[0078] The coupling or connection between the elements can be any suitable coupling or path, such as electrical wiring. In other examples, the structure of aircraft 101 itself can be part of the coupling. Aircraft electrical loads 130 can be any other element, component, and / or system within the aircraft, including heaters, pumps, generators, lighting systems, electrical systems, audio systems, or communication systems, to name a few.

[0079] Now refer to Figure 9 , describes an example of a system 900 with multiple CPDs. Figure 1 and Figure 2 , system 900 includes aircraft power source 102 , shorting switch 110 , first voltage sensor 116 , second voltage sensor 117 , current sensor 118 , resistor 120 , aircraft electrical load 130 , and controller 132 . Figure 1 and Figure 2 Other elements shown in FIG. 1 may include Figure 9 But for simplicity, Figure 9 These components have been omitted in the Figure 1 and Figure 2 , and that description will not be repeated here.

[0080] Figure 9 The system includes a first CPD 150, a second CPD 152, and a third CPD 154, rather than a single CPD 113 (e.g., Figure 1 and Figure 2 ). Although all of the first CPD 150, the second CPD 152, and the third CPD 154 are shown as connected to a single aircraft electrical load 130, it will be appreciated that each of the first CPD 150, the second CPD 152, and the third CPD 154 can be connected to a separate aircraft electrical load. In this case, the voltage across and the current through each of the first CPD 150, the second CPD 152, and the third CPD 154 can be measured separately.

[0081] In operation, controller 132 controls operation of first CPD 150 , second CPD 152 , third CPD 154 , and shorting switch 110 based on measured voltage from first voltage sensor 116 , measured voltage from second voltage sensor 117 , and measured current from current sensor 118 .

[0082] It should now be appreciated that circuit protection devices and structures are provided that prevent damage to sensitive switching devices deployed within power supply systems, sometimes referred to herein as main switching devices or circuit protection devices (CPDs). In one aspect, a shorting switch is used to divert a rupture or fault current away from the main switching device or CPD during a short circuit event.

[0083] Further aspects of the present disclosure are provided by the subject matter of the following clauses:

[0084] A system comprising: a circuit protection device (CPD) having an input coupled to an aircraft power source and an output coupled to an aircraft electrical load; a shorting switch coupled to the input of the CPD, wherein the shorting switch, when closed, provides a fault current path back to the aircraft power source and avoids passing through the CPD; a controller coupled to the CPD, the shorting switch, at least one voltage sensor, and at least one current sensor, the controller being configured to: receive a voltage measurement from the at least one voltage sensor and a current measurement from the at least one current sensor; and selectively open and close one or more of the CPD and the shorting switch based on the voltage measurement and the current measurement.

[0085] The system of any of the preceding clauses, wherein the CPD comprises a bypass switch and a micro-electromechanical systems (MEMS) device.

[0086] A system as in any of the preceding clauses, wherein the CPD comprises a MOSFET switch.

[0087] A system as in any of the preceding clauses, wherein the aircraft power source is a generator converter or a battery.

[0088] A system according to any of the preceding clauses, wherein the aircraft electrical load is a pump, a heating element or a power distribution device.

[0089] The system of any of the preceding clauses, wherein the shorting switch is an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET).

[0090] A system as in any of the preceding clauses, wherein the voltage sensor comprises a first sensor coupled to the input of the CPD and a second sensor coupled between the input of the CPD and an output of the CPD.

[0091] A system comprising: a microelectromechanical system (MEMS) device having an input coupled to an aircraft power source and an output coupled to an aircraft electrical load; a bypass switch electrically coupled in parallel with the MEMS device, the bypass switch providing a first alternative current path around the MEMS device when closed; a shorting switch coupled to the input of the MEMS device and the input of the bypass switch, wherein the shorting switch provides a second alternative current path when closed that returns to the aircraft power source and avoids the MEMS device and the aircraft electrical load; a controller coupled to the bypass switch, the shorting switch, at least one voltage sensor, the MEMS device, and at least one current sensor, the controller being configured to: receive a voltage measurement from the at least one voltage sensor and a current measurement from the at least one current sensor; and selectively open and close one or more of the MEMS device, the bypass switch, and the shorting switch based on the voltage measurement and the current measurement.

[0092] The system of any of the preceding clauses, wherein the bypass switch is a MOSFET.

[0093] The system of any of the preceding clauses, wherein the shorting switch is an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET).

[0094] A system as in any of the preceding clauses, wherein the aircraft power source is a generator, a converter or a battery.

[0095] A system according to any of the preceding clauses, wherein the aircraft electrical load is a pump, a heating element or a power distribution device.

[0096] The system of any of the preceding clauses, wherein the controller compares the measured current to a first threshold and a second threshold in determining whether to open or close the bypass switch and the shorting switch.

[0097] The system of any of the preceding clauses, wherein the controller compares the measured voltage to various thresholds in determining whether to open or close the bypass switch and the shorting switch.

[0098] A system according to any of the preceding clauses, wherein the controller compares the measured current to a first threshold and a second threshold in determining whether to open or close the bypass switch and the shorting switch, and wherein the controller compares the measured voltage to various thresholds in determining whether to open or close the bypass switch and the shorting switch.

[0099] A system as in any of the preceding clauses, wherein the fuse is electrically coupled in series with the shorting switch.

[0100] The system of any of the preceding clauses, wherein the at least one voltage sensor comprises a first voltage sensor coupled to an input of the MEMS device and a second voltage sensor coupled between the input of the MEMS device and an output of the MEMS device.

[0101] A method includes providing a bypass switch electrically coupled in parallel with a microelectromechanical system (MEMS) device, the bypass switch providing a first alternative current path around the MEMS device when closed, the MEMS device having an input coupled to an aircraft power source and an output coupled to an aircraft electrical load; providing a shorting switch coupled to an input of the MEMS device and an input of the bypass switch, wherein the shorting switch provides a second alternative current path back to the aircraft power source and avoiding a CPD and the aircraft electrical load when closed; receiving, at a controller, voltage measurements from at least one voltage sensor and current measurements from at least one current sensor; and selectively opening and closing, at the controller, one or more of the MEMS device, the bypass switch, and the shorting switch based on the voltage measurements and the current measurements.

[0102] The method of any of the preceding clauses, wherein the short-circuiting switch is an insulated gate bipolar transistor (IGBT) or a MOSFET.

[0103] A method according to any of the preceding clauses, wherein the controller compares the current measurement to a first threshold current and a second threshold current in determining whether to open or close the bypass switch and the shorting switch.

[0104] A method as in any of the preceding clauses, wherein the controller compares the voltage measurement to one or more threshold voltages in determining whether to open or close the bypass switch and the shorting switch.

[0105] A method as described in any of the preceding clauses, wherein the controller compares the current measurement to a first threshold current and a second threshold current in determining whether to open or close the bypass switch and the shorting switch, and wherein the controller compares the voltage measurement to one or more threshold voltages in determining whether to open or close the bypass switch and the shorting switch.

[0106] Those skilled in the art will recognize that various modifications, changes, and combinations of the above-described embodiments may be made without departing from the scope of the present disclosure, and such modifications, changes, and combinations are to be considered within the scope of the concepts described herein.

Claims

1. A system comprising: a circuit protection device (CPD) having an input coupled to an aircraft power source and an output coupled to an aircraft electrical load; a shorting switch coupled to the input of the CPD, wherein the shorting switch, when closed, provides a fault current path back to the aircraft power source and avoids passage through the CPD and the aircraft electrical loads; and a controller coupled to the CPD, the shorting switch, at least one voltage sensor, and at least one current sensor, the controller configured to: receiving a voltage measurement from the at least one voltage sensor and a current measurement from the at least one current sensor; and One or more of the CPD and the shorting switch are selectively opened and closed based on the voltage measurement and the current measurement.

2. The system according to claim 1, wherein: The CPD includes a bypass switch and a micro-electromechanical system (MEMS) device.

3. The system according to claim 1, wherein: The CPD includes a metal oxide semiconductor field effect transistor (MOSFET) switch.

4. The system according to claim 1, wherein: The aircraft power source is a generator, a power converter or a battery.

5. The system according to claim 1, wherein: The aircraft electrical loads are pumps, heating elements or electrical distribution equipment.

6. The system according to claim 1, wherein: The short-circuiting switch is an insulated gate bipolar transistor (IGBT) or a MOSFET.

7. The system according to claim 1, wherein: The at least one voltage sensor includes a first sensor coupled to the input of the CPD and a second sensor coupled between the input of the CPD and the output of the CPD.

8. A system comprising: a microelectromechanical system (MEMS) device having an input coupled to an aircraft power source and an output coupled to an aircraft electrical load; a bypass switch electrically coupled in parallel with the MEMS device, the bypass switch providing a first alternative current path around the MEMS device when closed; a shorting switch coupled to the input of the MEMS device and an input of the bypass switch, wherein the shorting switch provides a second alternative current path when closed that returns to the aircraft power source and avoids the MEMS device and the aircraft electrical loads; as well as a controller coupled to the bypass switch, the shorting switch, at least one voltage sensor, the MEMS device, and at least one current sensor, the controller configured to: receiving a voltage measurement from the at least one voltage sensor and a current measurement from the at least one current sensor; as well as One or more of the MEMS device, the bypass switch, and the shorting switch are selectively opened and closed based on the voltage measurement and the current measurement.

9. The system according to claim 8, wherein: The bypass switch is a metal oxide semiconductor field effect transistor (MOSFET).

10. The system according to claim 8, wherein: The short-circuit switch is an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET).

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