High voltage system discharge apparatus and method

Abstract

A method of discharging electrical power can include rotating a fan with an electric motor to provide kinetic energy (204' 204'), opening a disconnect switch to disconnect an electrical power source from the electric motor (206; 206' or 206"), generating electrical power by rotating the electric motor using the kinetic energy (208; 208'), providing electrical power generated by the electric motor to a microcontroller (212; 212'), bringing the fan to a controlled stop (216; 216'), and dissipating electrical power from an inverter power module connected to the electric motor through the electric motor as heat (218; 218'). Also disclosed is a high voltage system discharge apparatus, as well as a vehicle (50) including the same.

Description

HIGH VOLTAGE SYSTEM DISCHARGE APPARATUS AND METHODCROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] The present application is based on and claims the benefit and priority of U.S. provisional patent application Serial No. 63 / 548,574, filed February 1, 2024.FIELD

[0002] The present invention relates generally to an apparatus and method for discharging high voltage electricity, such as for a high voltage system in a vehicle or for high voltage industrial equipment.BACKGROUND

[0003] Initiatives are underway to limit greenhouse gas emissions and other types of emissions, including CO2 and NOXemissions. In pursuit of those objectives, alternative powertrains are being developed to replace an internal combustion engine. These include powertrain applications for vehicles like heavy-duty trucks and off-highway vehicles such as construction and mining equipment (for example, excavators, graders, loaders, and mining vehicles and equipment) with relatively high torque capacities. A need exists to provide cooling for a variety of systems on these types of equipment and vehicles. Electric powertrains on such vehicles typically consist of motors, electronic drives (often referred to as inverters), and mechanical transmissions. These devices are powered by an energy source such as a battery or fuel cell. Those energy sources are typically carried on the vehicle along with the electric powertrain. Hybrid vehicles that include both an internal combustion engine and an alternative drive are also possible. All these types of vehicles can still require significant cooling to protect their on-board systems from thermal damage.

[0004] Many such electrically-powered drivetrains are intended to operate at high voltages in order to constrain the size of electrical conductors, such as in the range of (nominally) approximately 400 to 1200 volts direct current (VDC), or in the range of approximately 450 to 850 VDC, as another example. On-board vehicle cooling systems will generally be powered by the same on-board energy sources as the electric powertrain, and at least some cooling system components will therefore operate at the same high voltages.

[0005] Vehicles may be involved in crashes or the like. In the event of a problem with the vehicle, it may be desired to provide a safe state, in which a risk of exposure to high-voltage power is reduced or eliminated. This helps enhance safety for passengers, first-responders to a crash, mechanics and other maintenance personnel, and others. Similarly, a fan of a cooling system should cease spinning or at least slow spinning in a safe state, which likewise can help enhance safety for any persons present. However, reaching a safe state presents difficulties in terms of ensuring that desired actions to reach that safe state are taken sufficiently quickly by components that normally rely on an electrical power source that is being shut down, while also ensuring that electrical power in the form of capacitance(s) is discharged. In other words, it is not sufficient to reach a safe state to simply cut off an electrical power supply, due to capacitances and kinetic energy present in vehicle systems.

[0006] It is desired to provide a cooling fan system (or other high voltage motor system) able to discharge high voltage electrical power in order to reach a safe state within a specified time period. Additionally, it is desired for such a cooling fan system to be able to stop rotation of the fan(s) with the specified time period to establish the safe state. Moreover, it is desired to provide methods achieving a safe state involving high voltage discharge. Desired solutions should be suitable for use in vehicular applications.SUMMARY

[0007] In one aspect, a method of discharging electrical power can include rotating a fan with an electric motor to provide kinetic energy, opening a disconnect switch to disconnect an electrical power source from the electric motor, generating electrical power by rotating the electric motor using the kinetic energy; providing electrical power generated by the electric motor to a microcontroller, bringing the fan to a controlled stop, and dissipating electrical power from an inverter power module connected to the electric motor through the electric motor as heat.

[0008] In another aspect, a high voltage system discharge apparatus can include an inverter including: a microcontroller, a power module including inverter circuitry with a plurality of electronic switching devices and rectifier circuitry, with the power module being controlled by the microcontroller, a high voltage disconnect switch connected to the power module, a DC / DC converter electrically connected to the power module, and an internal low voltage power connection connected between the DC / DC converter and the microcontroller; a motor having atleast one winding, the motor being electrically connected to the power module; a mechanical output device operably connected to the motor, with the mechanical output device being rotatable; and instructions stored in a non-transitory medium and executable by the microcontroller to cause the inverter to: control operation of the motor to rotate the mechanical output device to provide kinetic energy, control operation of the motor to generate electrical power using the kinetic energy, utilize electrical power generated by the motor to operate the microcontroller, control operation of the motor to bring the mechanical output device to a controlled stop, and control operation of the motor to dissipate electrical power from the power module through the motor as heat. In some embodiments, the method can optionally further include dissipating electrical power from an external electric device through the electric motor as heat.

[0009] In another aspect, a vehicle can include a high voltage system discharge apparatus, a high voltage power supply, an external disconnect switch, a high voltage bus (for example, with the high voltage disconnect switch connected between the high voltage bus and the power module, and the external disconnect switch connected between the high voltage power supply and the high voltage bus), an external device electrically connected to the high voltage bus, an electronic control unit, and a communications bus connected to the microcontroller and the electronic control unit. In some embodiments, the high voltage system discharge apparatus of the vehicle can include an inverter including: a microcontroller, a power module including inverter circuitry with a plurality of electronic switching devices and rectifier circuitry, with the power module being controlled by the microcontroller, a high voltage disconnect switch connected to the power module, a DC / DC converter electrically connected to the power module, and an internal low voltage power connection connected between the DC / DC converter and the microcontroller; a motor having at least one winding, the motor being electrically connected to the power module; a mechanical output device operably connected to the motor, with the mechanical output device being rotatable; and instructions stored in a non-transitory medium and executable by the microcontroller to cause the inverter to: control operation of the motor to rotate the mechanical output device to provide kinetic energy, control operation of the motor to generate electrical power using the kinetic energy, utilize electrical power generated by the motor to operate the microcontroller, control operation of the motor to bring the mechanical output device to a controlled stop, and control operation of the motor to dissipate electrical power from the power module through the motor as heat.

[0010] In yet another aspect, a method of discharging high voltage electrical power can include receiving a safe state command with a microcontroller, rotating a mechanical output device (for example, a fan) with an electric machine to provide kinetic energy (the electric machine being electrically driven by a power module having inverter circuitry that includes a plurality of electronic switching devices), opening a disconnect switch connected between a bus and the power module such that opening the disconnect switch disconnects the electric machine from electrical power available from the bus, generating high voltage electrical power by rotating the electric machine using the kinetic energy, rectifying the high voltage electrical power generated by the electric machine from high voltage AC power to high voltage DC power, converting the high voltage DC power to lower voltage DC power, providing the lower voltage DC power to the microcontroller, bringing the mechanical output device to a controlled stop by a time limit, and dissipating electrical power from the power module through a winding of the electric machine as heat. In some embodiments, the method can optionally further include dissipating electrical power from an external electric device through the electric machine as heat.

[0011] The present summary is provided only by way of example, and not limitation. Other aspects of the present invention will be appreciated in view of the entirety of the present disclosure, including the entire text, claims, and accompanying figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a schematic block diagram of an embodiment of a vehicle with a high voltage cooling fan system.

[0013] FIG. 2A is a schematic block diagram of an embodiment of a high voltage cooling system in a normal operation state.

[0014] FIG. 2B is a schematic block diagram of the high voltage cooling system of FIG. 2A in a safe state.

[0015] FIG. 3 is a flow chart illustrating an embodiment of a method of actively discharging high voltage power according to the present invention.

[0016] FIG 4 is a flow chart illustrating an alternate embodiment of a method of actively discharging high voltage power according to the present invention.

[0017] While the above-identified figures set forth one or more embodiments of the present invention, other embodiments arc also contemplated as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps, and / or components not specifically shown in the drawings.DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0018] Embodiments of the present invention generally provide an apparatus and method for discharging high voltage electrical power from a high voltage cooling fan system or other high voltage motor system, and optionally also high voltage electrical power from one or more additional external devices, through the high voltage cooling fan system (or other high voltage motor system) in order to provide a safe state. Such a safe state can help reduce or avoid exposure of nearby persons to high voltages and associated risks of electric shocks. Such a safe state can be triggered by receipt of a safe state command, such as a safe state signal generated by, or as a function of, detection of a crash by a crash sensor, for example. In some embodiments, a safe state can mean that all electrical power present in a given device or component is less than 60 volts DC (VDC) and / or less than 30 volts AC (VAC). Additionally, the safe state can stop rotation of all fan(s). The safe state can be achieved within a specified time period, such as five seconds or less. At least in some situations, electrical power can be generated using a motor of the high voltage cooling fan system (or other high voltage motor system) in order to power a microcontroller of that system in case of loss of low voltage power from a source used during normal operation, such as a vehicle-wide low voltage power source. Abrupt loss of low voltage power, such as due to a safe state command or failure, would result in the microcontroller “dying” and ceasing to function without the system entering the safe state. Yet the microcontroller is typically needed in order to provide appropriate control commands to place the system into the safe state. In such situations, the high voltage cooling fan system (or other high voltage motor system) can be used to generate power. An electric machine or dynamo-electric machine is generally capable of acting as a motor that uses electrical power to generate mechanical torque or as a generator that uses a torque input to generate electricity. That capability of electric machines can be used to temporarily utilize themotor to generate electricity, after the safe state command is received, using kinetic energy that is available as the motor spins down. In this way, the high voltage cooling fan system (or other high voltage motor system) can generate high voltage power and convert at least some of that high voltage power to low voltage power usable to power the microcontroller temporarily. After the motor is eventually stopped, electrical power generation would stop and thus the microcontroller may become unpowered, but it is possible to achieve the safe state before the microcontroller loses power or potentially loses power.

[0019] In some embodiments, activation of the safe state can involve making an initial evaluation of discharge needs and discharge apparatus capabilities, disconnecting a high voltage power bus (or other high voltage power source), discharge of high voltage capacitance through fan motor windings and generation of electrical power through rotation of a fan and associated motor rotor, rectification of AC power to DC power, conversion of at least some high voltage DC power to lower voltage DC power, powering a microcontroller with the generated low voltage DC power, making a controlled stop of fan rotation, discharging additional high voltage power through fan motor windings and / or an optional brake resistor through heat dissipation, and placing the microcontroller in a safe state mode (for example, a sleep / hibernation mode or unpowered mode). In some embodiments, electrical power from one or more external devices can also be discharged through the fan motor before disconnecting the high voltage power bus. Moreover, in some embodiments, an internal low voltage switch can be closed to when generating low voltage power for the microcontroller. Numerous other features and benefits of the present invention will be recognized by persons of ordinary skill in the art in view of the entirety of the present disclosure, including the accompanying drawings. For instance, although described with reference to embodiments involving a cooling fan, the present invention is also usable for other applications, such as with high voltage pump systems for pumping liquids.

[0020] FIG. I is a schematic block diagram of an embodiment of a vehicle 50 with a high voltage cooling fan system 52. As shown in the embodiment of FIG. 1, the vehicle 50 has various on-board systems including electrically-powered devices 53 (such as a traction motor, other types of electric motors, an electric heater, an electric pump, control / power electronics, etc.), a high voltage electrical power supply 55 (e.g., batteries and / or fuel cells), a heat exchanger assembly 57, and the high voltage cooling fan system 52 (shown with an optional associated circulating pump 52P). Various additional on-board systems, including a compressor 59C, an evaporator 59E, pump61, an optional valve 63, etc., are illustrated in FIG. 1 as examples of components that could be used as part of separate on-board cooling systems used in addition to the high voltage cooling fan system 52. Moreover, an example electronic control unit (ECU) 65 (also called an electronic control module (ECM)) with processing and control functionality is shown (e.g., an on-board vehicle computer). Although not depicted separately in FIG. 1, the high voltage electrical power supply 55 can include an inductive charging subsystem in some embodiments where the high voltage electrical power supply 55 includes batteries. Certain electrical connections between components for power supply and / or communications signals are shown in dashed lines in FIG 1; however, for simplicity, not all electrical connections are specifically shown in FIG. 1 and additional such electrical connections can be provided as desired and as would be understood by persons of ordinary skill in the art.

[0021] As shown in FIG. 1, the high voltage cooling fan system 52 can be positioned near the heat exchanger assembly 57 in order to move cooling air through the heat exchanger assembly 57. The high voltage cooling fan system 52 can include one or more motor(s), one or more fan(s), and one or more electronic control modules (often referred to simply as an inverter), relevant details of which are explained further elsewhere with reference to FIGS. 2A and 2B. In some embodiments, the high voltage cooling fan system 52 can be the same or similar to a configuration disclosed in commonly-assigned PCT International Patent Application Pub. No. WO 2023 / 178301 Al, for example. However, the present invention can also be used with other types or configurations of high voltage electric cooling fan systems.

[0022] In some embodiments, the heat exchanger assembly 57 can include multiple discrete liquid / air heat exchangers arranged as an axial stack and / or in a side-by-side array. FIG. 1 illustrates an embodiment with an axially stacked heat exchanger assembly 57 that includes first and second liquid-to-air heat exchangers (or radiators) 57A and 57B, and a condenser 57C. In embodiments where the high voltage cooling fan system 52 includes a liquid cooling circuit C, that liquid cooling circuit C can be tied to at least one liquid / air heat exchanger (radiator) 57B in the heat exchanger assembly 57. The condenser 57C can operate with the compressor 59C and the evaporator 59E as part of a chiller or air conditioning system, and the radiator 57A can remove waste heat from liquid coolant used to cool the vehicle’s traction motor (as one of the electrically- powered devices 53, but not shown more specifically in FIG. 1), for example.

[0023] FIG. 2A is a schematic block diagram of an embodiment of the high voltage cooling fan system 52 in a normal operation state, and FIG. 2B is a schematic block diagram of the high voltage cooling fan system 52 in a safe state. As shown in FIGS. 2A and 2B, the high voltage cooling fan system 52 can include an inverter assembly 100 having a power module 102, gate drive circuitry 104, a microcontroller 106, a low voltage (LV) power module 108, a diode 110, a DC / DC converter 112, an internal LV power connection 114, and a high voltage (HV) disconnect switch 116. The inverter assembly 100 can further include an enclosure 118. The high voltage cooling fan system 52 can further include at least one motor (or electric machine) 120 and at least one fan 122. Also shown in FIGS. 2A and 2B are selected external components, including a vehicle / application HV bus 130, an application LV power source 132, an ECU communications bus 134, an optional vehicle crash signal source 136, external device(s) 138, and an optional external disconnect switch 140. The configuration shown in FIGS. 2A and 2B is presented merely by way of example and not limitation. For instance, the high voltage cooling fan system 52 can include additional components not specifically shown, and can be used with non-vehicular industrial applications as well.

[0024] Although referred to herein as an “inverter” assembly 100, that assembly 100 can also include circuitry for other functions, such as communications, filtering, etc. Most generally, the inverter assembly 100 can function as an electronic drive and controller for the motor(s) 120, as discussed in PCT International Patent Application Pub. No. WO 2023 / 178301 Al, for example. As shown in the illustrated embodiment, the inverter assembly 100 is electrically connected to at least one of the motor(s) 120, and at least one of the fan(s) 122 is mechanically connected to each of the motor(s) 120. In various embodiments, a single inverter assembly 100 could be operably connected to multiple motors 120 or only a single motor 120. The number of motor(s) 120 and fan(s) 122 can vary as desired for particular applications. Each motor 120 includes one or more winding(s) 120-1, and can further optionally include one or more brake resistor(s) 120-2. In some embodiments, the motor(s) 120 can have a permanent magnet synchronous motor configuration such as a three-phase brushless DC (BLDC) design. Torque generated by the motor(s) 120 can rotate the fan(s) 122 to create airflows.

[0025] As shown in FIGS. 2 A and 2B, the power module 102 includes inverter circuitry (or switch circuitry) 102-1 with high-speed electronic switching devices, such as insulated-gate bipolar transistors (IGBTs) or Silicon carbide (SiC) metal-oxide-semiconductor field-effecttransistors (MOSFETs), and rectifier circuitry 102-2, such as a diode-bridge rectifier, as well as any other desired circuitry (for example, filter circuitry). The power module 102 can create quasi- AC high voltages from DC high voltages, and can selectively supply power to the motor(s) 120, and to the winding(s) 120-1 of those motor(s) 120, to in turn selective control rotation of the fan(s) 122. The gate drive circuitry 104 is connected to both the microcontroller 106 and the power module 102, and facilitates driving the power electronics (for example, the inverter circuitry 102- 1) of the power module 102 under the control of the microcontroller 106.

[0026] The power module 102 is powered by high voltage power, which can be supplied to the inverter assembly 100 from the external vehicle / application HV bus 130. The external vehicle / application HV bus 130 can be electrically connected to a number of distinct devices or assemblies, including the high voltage cooling fan system 52, to commonly supply high voltage power to them all. The HV disconnect switch 116 is connected in between the vehicle / application HV bus 130 and the power module 102. In the normal operation state shown in FIG. 2A, the HV disconnect switch 116 is closed to allow high voltage power to be supplied to the power module 102. In the safe state mode shown in FIG. 2B, the HV disconnect switch 116 is open, such that high voltage current cannot flow between the vehicle / application HV bus 130 and the power module 102. Operation of the HV disconnect switch 116 can be controlled by the microcontroller 106, for example.

[0027] The external device(s) 138 are each high voltage devices connected to and powered by the vehicle / application HV bus 130. In various embodiments, these external device(s) 138 can encompass one or more devices shown in FIG. 1, such as the circulating pump 52P, the electrically- powered devices 53, and / or the pump 61, and / or one or more other devices not specifically shown in FIG. 1.

[0028] The application EV power source 132 supplies power to the EV power module 108 through the diode 110, and the LV power module 108 further supplies low-voltage power to the microcontroller 106, which in turn provides low voltage signals to the gate drive circuitry 104. The LV power module 108 can include filtering circuitry, as desired for particular applications.

[0029] The microcontroller 106 can include one or more processors, and can include or be operatively connected to computer-readable memory that stores suitable executable software and / or firmware instructions in a non-transitory format. The microcontroller 106 is further operatively connected to the ECU 65, such as via the ECU communications bus 134, in order toexchange communications signals with the ECU 65 in a suitable format (for example, Controller Area Network (CAN) format signals compliant with Society of Automotive Engineers (SAE) standard SAE J1939). The optional vehicle crash signal source 136, such as a crash sensor or other crash determination device, can also be operatively connected to the microcontroller 106. One or both of the ECU 65 and the vehicle crash signal source 136 are capable of sending a safe state command signal (or crash signal) to the microcontroller. A gate (for instance, an OR / NOR gate), multiplexer, or the like 142 can optionally be provided between the ECU communications bus 134 and the vehicle crash signal source 136 and the microcontroller 106, in some embodiments.

[0030] The inverter assembly 100 of the illustrated embodiment further includes the DC / DC converter 112 and the internal LV power connection 114 operatively connected between the power module and the LV power module. The DC / DC converter 112 can be configured to convert high voltage power to low voltage power, such that in the safe state low voltage power can be supplied to at least the microcontroller 106 (as explained further elsewhere in the present disclosure). In some embodiments, the nominal low voltage power supplied to the microcontroller 106 can be 12 VDC, 24 VDC, or another suitable voltage level that is less than 60 VDC. The internal LV power connection 114 can be or include, for example, a diode or a switch. In embodiments using a diode, low voltage current can flow only in one direction from the DC / DC converter 112 to the LV power module 108. Such a configuration has the advantage of simplicity because there is no active control or other action required to supply low voltage power from the DC / DC converter to the LV power module in the safe state mode, while still allowing normal operation to occur without interference or short circuiting due to the presence of the internal LV power connection 114. In other embodiments, the internal LV power connection 114 can be a switch that can be open during normal operation and closed in the safe state mode.

[0031] FIG. 3 is a flow chart illustrating an embodiment of a method of actively discharging high voltage power, which can be implemented using the high voltage cooling fan system 52. The method begins with the microcontroller 106 receiving a safe state command (Step 200). The safe state command can be in the form of one or more signals from the ECU 65 and / or the (optional) vehicle crash signal source 136. The safe state command can represent a need for high voltages to be discharged within a given period of time. For example, following a vehicle crash or when there is a need to enter a maintenance mode, high voltages can be discharged so that persons nearby have less risk of exposure to high voltages.

[0032] After a safe state command is received, a discharge evaluation can be performed (Step 202). This discharge evaluation can involve determining how much high voltage power is desired to be discharged and the capabilities of the high voltage cooling fan system 52 to discharge electrical power, and can further involve assessment of the need for initial action to adjust variable discharge capabilities. The discharge evaluation can be performed by the microcontroller 106. The microcontroller 106 can determine how much high voltage power is desired to be discharged, as a function of high voltage capacitances within the inverter assembly 100. Such a determination could be the result of analysis of sensed information or, alternatively, as a fixed or predetermined stored value based upon a probable, maximum, or other capacitance value. Additionally, the microcontroller 106 can determine fixed and variable discharge capabilities. Fixed discharge capabilities can include a predetermined, stored value, such as a value based upon information related to the number and size of the motor(s) 120, ratings of the winding(s) 120-1 of the motor(s) 120, the presence of any brake resistor(s) 120-2, and the like, which can characterize maximum capabilities of the high voltage cooling fan system 52 to discharge high voltage power. Variable discharge capabilities can include information related to the current operational state of the high voltage cooling fan system 52, such as the present rotational speed(s) of the fan(s) 122, operational status of the motor(s) 120 (e.g., loss of functionality in particular motor(s) 120 due to a vehicle crash), and the like, which can relate to controllable aspects of the discharge method. Moreover, in some embodiments, the discharge evaluation can further involve assessing whether or not low voltage power is still available, and using that information to adjust later steps in the method.

[0033] If the fan(s) 122 are not rotating, or not rotating at a sufficient speed, as determined by the discharge evaluation, then one or more of the fan(s) 122 can be rotated (Step 204). In some embodiments, the fan(s) 122 are rotated to a maximum possible speed (for example, approximately 3000 RPM) within a given time limit. Such rotation can be specified by a command from the microcontroller 106. Fan rotation at this step is the result of powering the corresponding motor(s) 120 in a manner similar to that of normal operation, but only for a relatively short length of time in order that the entire active discharge method can still be completed within a specified time limit. For example, the rotation of the fan(s) 122 can occur for a desired percentage of the time limit for the entire active discharge method, such as up to 10%, 25%, 33%, 50%, or another desired percentage. By rotating the fan(s) 122, kinetic energy is imparted to the fan(s) 122. The availability of kinetic energy in the fan(s) 122, and associated rotor components of the motor(s)120, provides an energy source (or store) that is independent of the vehicle / application HV bus 130 and also mechanical and non-clcctrical and non-chcmical in nature. In other words, the fan(s) 122 and associated components (such as a rotor of the corresponding motor 120) can temporarily act like flywheels in order to facilitate completion of desired high voltage power active discharge. If multiple fans 122 are available, rotation might be imparted or increased in speed to some but not all of them, in some embodiments and / or situations. The objective of this step is primarily to ensure that sufficient kinetic energy is available for later steps. In this sense, rotation of the fan(s) 122 can be independent from cooling or other airflow generation requirements. Alternatively, if the fan(s) 122 are already rotating at a sufficient speed that adequate kinetic energy is already available, then the Step 204 of rotating the fan(s) can essentially be skipped.

[0034] Next the vehicle / application HV bus 130 is disconnected by opening the HV disconnect switch 116 (Step 206). At this step, the power module 102 and the rest of the circuitry of the inverter assembly 100 is effectively isolated from the external high voltage power supply represented by the vehicle / application HV bus 130, and no additional high voltage current will flow into the inverter assembly 100 through the normal supply line(s). Merely opening the HV disconnect switch 116 to disconnect the high voltage power supply will generally still leave high voltage capacitance within the inverter assembly 100, which will then be dissipated in subsequent steps. The method can proceed further even if low voltage power is unavailable from the time that the HV disconnect switch 116 is opened, such as being unavailable externally from the application LV power source 132; however, in some embodiments and / or situations, low voltage power may remain available, at least for some additional amount of time.

[0035] Next the available kinetic energy associated with the rotating fan(s) 122 can be used to generate high voltage electrical power using the associated motor(s) 120 (Step 208). This electrical generation can be similar to regenerative braking, for example. At the same time, that is, concurrently with high voltage electrical power generation, high voltage power present within the inverter assembly 100 desired to be discharged can be discharged through the motor(s) 120, through those motor(s)’ winding(s) 120-1. The microcontroller 106 can supervise this process. Further, the rectifier circuitry 102-2 of the power module 102 can rectify generated high voltage AC power to provide high voltage DC power output from the power module 102.

[0036] At least a portion of the generated high voltage DC power can then be converted to low voltage DC power (Step 10). This step can be performed using the DC / DC converter 112. Theconverted low voltage DC power can then be provided to the microcontroller 106 to power operation of the microcontroller 106 (Step 212). In some embodiments, the generated and converted low voltage power can be supplemented with low voltage power from an external low voltage power source, such as the source used for normal operation (for instance, the application LV power source 132). However, generating electrical power from available kinetic energy using the motor(s) 120 means that operation of the microcontroller 106 can continue even after the HV disconnect switch 116 is opened and even if the normal external low voltage power source is inadequate, unavailable, or disconnected. In this way, low voltage power supplied to the microcontroller 106 survives or persists even after loss or disconnection of the normal external high voltage power supply via the vehicle / application HV bus 130, which allows the microcontroller 106 to continue to operate to control the active discharge process through to its completion.

[0037] The method further includes evaluating an elapsed time since the safe state command was received against a high voltage discharge time limit (for example, five seconds from receipt of the safe state command) (Step 214). This step allows a determination of how much time remains before the high voltage discharge time limit is reached. The microcontroller 106 can access saved information about the high voltage discharge time limit and one or more shorter time period(s) reserved for specific actions that must be initiated and / or completed by or before the high voltage discharge time limit. If sufficient time remains before the high voltage discharge time limit, the method can return to the Step 208 of generating high voltage power and discharging power via the motor(s). If, however, the elapsed time approaches the high voltage discharge time limit, such as having reached a time limit to begin a late-stage sub-process, then the method can instead proceed toward a controlled stop step.

[0038] Prior to reaching the high voltage discharge time limit, the motor(s) and the fan(s) are brought to a controlled stop (Step 216). The microcontroller 106 can govern the controlled stop, in conjunction with the power module 102. In some embodiments, the fan(s) 122 and the motor(s) 120 may only need to reach a stopped (essentially zero RPM) state, but can be permitted to rotate again thereafter, either through passive windmilling or the like or by intention. Although in other embodiments the fan(s) 122 and the motor(s) 120 can remain stopped. By stopping rotation of the fan(s) 122, there is less risk of contact with a rotating fan 122 by persons nearby, and also less risk of unintended high voltage power generation in the motor(s) 120 that would undermine the desiredhigh voltage active discharge process. During the controlled stop, it is possible for additional power to be generated by the motor(s) 120 that can further be used to power the microcontroller 106, in some embodiments.

[0039] After the fan(s) 122 and the motor(s) 120 have stopped rotating, some or all of any remaining high voltage power to be discharged can be dissipated through the motor(s) 120 as heat (Step 218). For example, remaining high voltage power can be passed through the winding(s) 120-1 of one or more of the motor(s) 120, and / or through brake resistor(s) 120-2 in the motor(s) 120 (if present). It is possible for this step to involve heat dissipation through the same or different motor(s) 120 than were used for power generation in a previous step, in some embodiments that involve a system with multiple motors 120. Additionally, it is also possible for some of the high voltage power to be dissipated as heat in one or more of the motor(s) 120 at Step 218 concurrently with discharge through one or more other motor(s) 120 in connection with electrical generation at Step 208. That is to say, that in some embodiments the heat dissipation step (Step 218) could begin prior to all fans 122 completing the controlled stop at Step 216 and while Step 208 is still being performed for one or more other fan(s) 120. The microcontroller 106 can govern the heat dissipation process, which can involve applying electrical energy to the motor(s) 120 at levels or in ways that do not cause the motor(s) 120 to rotate the fan(s) 122, so that the fan(s) 122 can remain essentially stationary in some embodiments.

[0040] Eventually, the high voltage cooling fan system 52 reaches a high voltage safe state. Such a high voltage safe state can mean that the vehicle / application HV bus 130 is disconnected, high voltage capacitances within the high voltage cooling fan system 52 have been substantially or completely discharged such that all electrical power still present is less than 60 volts DC (VDC) and / or less than 30 volts AC (VAC), and the fan(s) 122 (and the motor(s) 120) brought to a stop. It is possible for a “safe touch” condition to be established in the high voltage safe state, such than any portions of the high voltage cooling fan system 52 are safe for a human to touch, allowing first responders, mechanics, or others to freely work on the vehicle 50 and the high voltage cooling fan system 52 following a crash. The high voltage safe state can be achieved within a relatively short period of time, such as within five seconds, according to embodiments of the present invention.

[0041] When, or after, a high voltage safe state has been achieved, the microcontroller 106 can enter a safe state mode (Step 220). Such a microcontroller safe state mode can be a sleep or hibernation mode, or an unpowered state, in various embodiments. In this way, the microcontroller106 can remain active and powered until the high voltage safe state has been reached, and only effectively shut down once the high voltage discharge process is essentially complete. Low voltage power supplied to the microcontroller 106 presents relatively low risk and therefore even if the microcontroller 106 remains in a hibernation or sleep state drawing some power the high voltage safe state and “safe touch” condition can still be maintained.

[0042] FIG 4 is a flow chart illustrating an alternate embodiment of a method of actively discharging high voltage power, which can involve discharging high voltage power from one or both the high voltage cooling fan system 52 and at least one external device 138 through the high voltage cooling fan system 52. Because many of the steps of this embodiment are similar to those discussed above with respect to FIG. 3, the more detailed descriptions of steps discussed above generally apply unless otherwise indicated. As in the preceding embodiment, the method begins with the microcontroller 106 receiving a safe state command (Step 200’), which can be in the form of one or more signals from the ECU 65 and / or the (optional) vehicle crash signal source 136.

[0043] After a safe state command is received, a discharge evaluation can be performed (Step 202’). This discharge evaluation can involve determining how much high voltage power is desired to be discharged and the capabilities of the high voltage cooling fan system 52 to discharge electrical power, and can further involve assessment of the need for initial action to adjust variable discharge capabilities. The discharge evaluation can be performed by the microcontroller 106. The microcontroller 106 can determine how much high voltage power is desired to be discharged, as a function of high voltage capacitances both within the inverter assembly 100 and those of external device(s) 138 connected to the vehicle / application HV bus 130. In this respect, the discharge evaluation of the illustrated embodiment of FIG. 4 specifically includes assessment of how much high voltage power from external device(s) 138 is desired to be discharged by the high voltage cooling fan system 52. Such a determination could be the result of analysis of sensed information, and / or signals sent via the ECU 65, and possibly augmented with fixed or predetermined stored value(s). Additionally, the microcontroller 106 can determine fixed and variable discharge capabilities. Fixed discharge capabilities can include a predetermined, stored value, such as a value based upon information about the high voltage cooling fan system 52 related to the number and size of the motor(s) 120, ratings of the winding(s) 120-1 of the motor(s) 120, the presence of any brake resistor(s) 120-2, and the like. Variable discharge capabilities can include information related to the current operational state of the high voltage cooling fan system52, such as the present rotational speed(s) of the fan(s) 122, operational status of the motor(s) 120 (c.g., loss of functionality in particular motor(s) 120 due to a vehicle crash), and the like. Depending on how much external high voltage power is desired to be discharged, the microcontroller 106 can send a signal to the ECU 65 indicating that the high voltage cooling fan system 52 lacks capacity to discharge all of the external power, thus allowing the ECU 65 to specify discharge of some external device high voltage power elsewhere or through other means. Lastly, the discharge evaluation can further involve assessing whether or not low voltage power is still available, and using that information to adjust later steps in the method, in some embodiments.

[0044] If the fan(s) 122 are not rotating, or not rotating at a sufficient speed, as determined by the discharge evaluation, then one or more of the fan(s) 122 can be rotated (Step 204’). As discussed above with respect to the prior embodiment, the fan(s) 122 can be rotated to a maximum possible speed (for example, approximately 3000 RPM) within a given time limit, to impart kinetic energy. Such rotation can be specified by a command from the microcontroller 106. For example, the rotation of the fan(s) 122 can occur for a desired percentage of the time limit for the entire active discharge method, such as up to 10%, 25%, 33%, 50%, or another desired percentage. If multiple fans 122 are available, rotation might be imparted or increased in speed to some but not all of them, in some embodiments and / or situations. Alternatively, if the fan(s) 122 are already rotating at a sufficient speed that adequate kinetic energy is already available, then the Step 204’ of rotating the fan(s) 122 can essentially be skipped.

[0045] At this point, based on the discharge evaluation, it is determined if active discharge of high voltage power from any external device(s) 138 is to be performed, or if discharge of only capacitance within the high voltage cooling fan system 52 is needed (Step 205). If power from any external device(s) 138 must be discharged, the HV disconnect switch 116 must remain closed, so that external high voltage power can be delivered from the vehicle / application HV bus 130 to the power module 102 across the HV disconnect switch 116. However, at this point the ECU 65 could disconnect the high voltage electrical power supply 55 (for example, a battery, fuel cell, or the like) from the vehicle / application HV bus 130 with the external disconnect switch 140 (Step 205 A), such that only stored capacitance from external device(s) 138 is discharged. The ECU 65 can open the external disconnect switch 140 based on a signal form the microcontroller 106 or, alternatively, independent from any action of the microcontroller 106, such as based on independent receipt of the safe state command. Otherwise, if only capacitance already within thehigh voltage cooling fan system 52 needs to be discharged, then the vehicle / application HV bus 130 can be disconnected by opening the HV disconnect switch 116 (Step 206’), and the method can proceed in essentially the same manner as discussed with respect to the embodiment shown in FIG. 3.

[0046] Next, the available kinetic energy associated with the rotating fan(s) 122 can be used to generate high voltage electrical power using the associated motor(s) 120, and the rectifier circuitry 102-2 of the power module 102 can provide high voltage DC power output (Step 208’). At the same time, that is, concurrently with high voltage electrical power generation, high voltage power desired to be discharged can be discharged through the motor(s) 120, through those motor(s)’ winding(s) 120-1. This can include discharge of both capacitance within the inverter assembly 100 as well as high voltage power from the external device(s) 138 delivered via the vehicle / application HV bus 130. The microcontroller 106 can supervise this process.

[0047] At least a portion of the generated high voltage DC power can then be converted to low voltage DC power (Step 210’). This step can be performed using the DC / DC converter 112. The converted low voltage DC power can then be provided to the microcontroller 106 to power operation of the microcontroller 106 (Step 212’). In some embodiments, the generated and converted low voltage power can be supplemented with low voltage power from an external low voltage power source, such as the source used for normal operation (for instance, the application LV power source 132).

[0048] The method further includes evaluating an elapsed time since the safe state command was received against a high voltage discharge time limit (for example, five seconds from receipt of the safe state command) (Step 214’). If sufficient time remains before the high voltage discharge time limit, the method can return to the Step 208’ of generating high voltage power and discharging power via the motor(s) 120. If, however, the elapsed time approaches the high voltage discharge time limit, such as having reached a time limit to begin a late-stage sub-process, then the method can instead proceed toward a controlled stop step.

[0049] Prior to reaching the high voltage discharge time limit, the motor(s) 120 and the fan(s) 122 are brought to a controlled stop (Step 216’). The microcontroller 106 can govern the controlled stop, in conjunction with the power module 102. In some embodiments, the fan(s) 122 and the motor(s) 120 may only need to reach a stopped (essentially zero RPM) state, but can be permitted to rotate again thereafter, or alternatively can remain stopped. During the controlledstop, it is possible for additional power to be generated by the motor(s) 120 that can further be used to power the microcontroller 106, in some embodiments.

[0050] After the fan(s) 122 and the motor(s) 120 have stopped rotating, some or all of any remaining high voltage power to be discharged can be dissipated through the motor(s) 120 as heat (Step 218’)- For example, remaining high voltage power can be passed through the winding(s) 120-1 of one or more of the motor(s) 120, and / or through brake resistor(s) 120-2 in the motor(s) 120 (if present). It is possible for this step to involve heat dissipation through the same or different motor(s) 120 than were used for power generation in a pervious step, and / or for some of the high voltage power to be dissipated as heat in one or more motor(s) 120 concurrently with discharge through one or more other motor(s) 120 in connection with electrical generation. The microcontroller 106 can govern the heat dissipation process, which can involve applying electrical energy to the motor(s) 120 at levels or in ways that do not cause the motor(s) 120 to rotate the fan(s) 122, so that the fan(s) 122 can remain essentially stationary in some embodiments.

[0051] The microcontroller 106 can eventually determine if the HV disconnect switch 116 is still closed or was previously opened (Step 219). In FIG. 4 this determination is shown as taking place after the heat dissipation of Step 218’ has begun, although in alternate embodiments this determination could be made earlier, such as before or during the controlled stop of Step 216’. The timing of the determination of HV disconnection status could also vary depending upon how much external high voltage power is sought to be dissipated (if very little, then this determination might happen relatively earlier). If the HV disconnect switch 116 is still closed, then the vehicle / application HV bus 130 is disconnected by opening the HV disconnect switch 116 (Step 206”). If the HV disconnect switch 116 was already opened, then Step 206” can essentially be skipped.

[0052] Eventually, the high voltage cooling fan system 52 reaches a high voltage safe state. Even with the active discharge of high voltage power from the one or more external device(s) 138, the high voltage safe state for the high voltage cooling fan system 52 can be achieved within a relatively short period of time, such as within five seconds, according to embodiments of the present invention. The high voltage cooling fan system 52 reaching a safe state does not necessarily mean that any external devices 138 have also reached a safe state, although in some embodiments all the external devices 138 actively discharged via the high voltage cooling fan system 52 can also reach a safe state at or near the same time. And when, or after, a high voltagesafe state has been achieved, the microcontroller 106 can enter a safe state mode (Step 220’). Such a microcontroller safe state mode can be a sleep or hibernation mode, or an unpowcrcd state, in various embodiments.

[0053] Although the preceding methods have been described with reference to fan motor(s), the same basic methods or a similar method could be used with other types of motors, such as an electric pump motor for circulating liquids. For example, an electric motor with a connected fluid impeller or other mechanical output device could be utilized instead of a motor with an attached fan. An example of a high voltage fluid pump and heater capable of pumping liquids is disclosed in commonly-assigned PCT International Patent Application Pub. No. WO 2024 / 050033 Al. To the extent that liquids present more resistance to freewheel-like operation to store kinetic energy, it is possible to use controllable valves to evacuate some or all liquid from a pump impeller volume such that the impeller (and associated components) can then spin more freely to retain kinetic energy like a flywheel in order to operate in a manner like a fan as described above to discharge high voltage power. Moreover, the methods described above could be implemented using a combination of fan and pump motors and either a common controller, such as the ECU 65, or set of controllers that remain powered by low voltage power during high voltage discharge.

[0054] After reviewing the entire present disclosure, persons of ordinary skill in the ail will appreciate that the present invention provides numerous advantages and benefits. For example, the active discharge of high voltage power can be performed without access or dependence upon normal power sources. And, in vehicular applications, the active discharge of high voltage power can be performed using auxiliary vehicle components, such as a fan or pump system, without the direct involvement of a traction motor, thereby allowing more flexibility in vehicle design and operation. Moreover, rather than require an auxiliary temporary power supply, such as a battery, to operate a microcontroller during active discharge, sufficient power can be generated from available kinetic energy using existing systems with a relatively small and nearly negligible added mass and / or size penalty. In contrast, an auxiliary battery could add additional mass and size to the system, and also present maintenance difficulties associated with sustaining a charge in an auxiliary battery that may rarely be used and may not be in an easily-accessed location for periodic replacement. Also, the kinds of flywheels, pumped storage, and other devices used for kinetic energy storage for grid power plants can not only present significant mass and space penalties but also may not be readily adapted for efficient use with vehicular applications in which vehiclemotion may inhibit operation or present reliability / failure concerns, particularly under crash conditions. For instance, some dedicated flywheels can be subject to shattering, which makes them less suited to active discharge for vehicular applications triggered upon a crash.

[0055] Discussion of Possible Embodiments

[0056] A method of discharging electrical power can include rotating a fan with an electric motor to provide kinetic energy; opening a disconnect switch to disconnect an electrical power source from the electric motor; generating electrical power by rotating the electric motor using the kinetic energy; providing electrical power generated by the electric motor to a microcontroller; bringing the fan to a controlled stop; and dissipating electrical power from an inverter power module connected to the electric motor through the electric motor as heat.

[0057] The method of the preceding paragraph can optionally include, additionally and / or alternatively, any one or more of the following features, configurations, and / or additional steps:

[0058] receiving a safe state command with the microcontroller as an initial step of the method;

[0059] evaluating an elapsed time since the safe state command was received against a time limit with the microcontroller, and initiating the controlled stop of the fan prior to reaching the time limit;

[0060] rectifying the electrical power generated by the electric motor from high voltage AC power to high voltage DC power;

[0061] converting the high voltage DC power to lower voltage DC power;

[0062] after the step of opening the disconnect switch to disconnect the electrical power source from the electric motor, closing a low voltage power connection switch that is connected between the inverter power module and the microcontroller;

[0063] placing the microcontroller in a safe state mode;

[0064] the step of dissipating electrical power from the inverter power module connected to the electric motor through the electric motor as heat can involve dissipating electrical power through a winding of the electric motor;

[0065] the step of dissipating electrical power from the inverter power module connected to the electric motor through the electric motor as heat can involve dissipating electrical power through a brake resistor of the electric motor;

[0066] dissipating electrical power from an external electric device through the electric motor as heat;

[0067] the step of opening the disconnect switch to disconnect the electrical power source from the electric motor can occur after the step of dissipating electrical power from the external electric device through the electric motor as heat; and / or

[0068] opening an external switch between the electrical power source and a bus, the bus being connected between the electrical power source and both the electric motor and the external electrical device.

[0069] A high voltage system discharge apparatus can include an inverter including: a microcontroller, a power module including inverter circuitry with a plurality of electronic switching devices and rectifier circuitry, with the power module being controlled by the microcontroller, a high voltage disconnect switch connected to the power module, a DC / DC converter electrically connected to the power module, and an internal low voltage power connection connected between the DC / DC converter and the microcontroller; a motor having at least one winding, the motor being electrically connected to the power module; a mechanical output device operably connected to the motor, with the mechanical output device being rotatable; and instructions stored in a non-transitory medium and executable by the microcontroller to cause the inverter to: control operation of the motor to rotate the mechanical output device to provide kinetic energy, control operation of the motor to generate electrical power using the kinetic energy, utilize electrical power generated by the motor to operate the microcontroller, control operation of the motor to bring the mechanical output device to a controlled stop, and control operation of the motor to dissipate electrical power from the power module through the motor as heat.

[0070] The high voltage system discharge apparatus of the preceding paragraph can optionally include, additionally and / or alternatively, any one or more of the following features, configurations, and / or additional components:

[0071] the mechanical output device can be a fan;

[0072] the internal low voltage power connection can be a diode or a switch controlled by the microcontroller;

[0073] the inverter can further include a diode arranged to prevent low voltage electrical power from passing out of the inverter to an external low voltage power source;

[0074] the motor can further include a brake resistor;

[0075] the instructions stored in the non-transitory medium and executable by the microcontroller can further cause the inverter to control operation of the motor to dissipate additional electrical power through the brake resistor; and / or

[0076] the inverter can further include an enclosure.

[0077] A vehicle can include: a high voltage system discharge apparatus; a high voltage power supply; an external disconnect switch; a high voltage bus, with the high voltage disconnect switch connected between the high voltage bus and the power module, and the external disconnect switch connected between the high voltage power supply and the high voltage bus; an external device electrically connected to the high voltage bus; an electronic control unit; and a communications bus connected to the microcontroller and the electronic control unit.

[0078] The vehicle of the preceding paragraph can optionally include, additionally and / or alternatively, any one or more of the following features, configurations, and / or additional components:

[0079] The high voltage system discharge apparatus can include an inverter including: a microcontroller, a power module including inverter circuitry with a plurality of electronic switching devices and rectifier circuitry, with the power module being controlled by the microcontroller, a high voltage disconnect switch connected to the power module, a DC / DC converter electrically connected to the power module, and an internal low voltage power connection connected between the DC / DC converter and the microcontroller; a motor having at least one winding, the motor being electrically connected to the power module; a mechanical output device operably connected to the motor, with the mechanical output device being rotatable; and instructions stored in a non-transitory medium and executable by the microcontroller to cause the inverter to: control operation of the motor to rotate the mechanical output device to provide kinetic energy, control operation of the motor to generate electrical power using the kinetic energy, utilize electrical power generated by the motor to operate the microcontroller, control operation of the motor to bring the mechanical output device to a controlled stop, and control operation of the motor to dissipate electrical power from the power module through the motor as heat;

[0080] a crash sensor configured to send a safe state command signal to the microcontroller;

[0081] the instructions stored in the non-transitory medium and executable by the microcontroller can further cause the inverter to control operation of the motor to dissipate electrical power from the external electric device through the motor as heat;

[0082] the electronic control unit can be configured to open the external disconnect switch between the high voltage power supply and the high voltage bus following issuance of a safe state command signal; and / or

[0083] the instructions stored in the non-transitory medium and executable by the microcontroller can further cause the inverter to evaluate an elapsed time since a safe state command was issued against a time limit using the microcontroller.

[0084] A method of discharging high voltage electrical power can include: receiving a safe state command with a microcontroller; rotating a mechanical output device with an electric machine to provide kinetic energy, the electric machine being electrically driven (to produce torque) by a power module having inverter circuitry that includes a plurality of electronic switching devices; opening a disconnect switch connected between a bus and the power module, such that opening the disconnect switch disconnects the electric machine from electrical power available from the bus; generating high voltage electrical power by rotating the electric machine using the kinetic energy; rectifying the high voltage electrical power generated by the electric machine from high voltage AC power to high voltage DC power; converting the high voltage DC power to lower voltage DC power; providing the lower voltage DC power to the microcontroller; bringing the mechanical output device to a controlled stop by a time limit; and dissipating electrical power from the power module through a winding of the electric machine as heat.

[0085] The method of the preceding paragraph can optionally include, additionally and / or alternatively, any one or more of the following features, configurations, and / or additional steps:

[0086] evaluating an elapsed time since the safe state command was received against a time limit using the microcontroller;

[0087] placing the microcontroller in a safe state mode;

[0088] dissipating electrical power through a brake resistor of the electric machine;

[0089] opening an external switch between an electrical power source and the bus;

[0090] dissipating electrical power from an external electric device through the electric machine as heat;

[0091] the step of opening the external switch between the electrical power source and the bus can occur before the step of dissipating electrical power from the external electric device through the electric machine as heat; and / or

[0092] after the step of opening the disconnect switch connected between the bus and the power module, closing a low voltage power connection switch that is connected between the power module and the microcontroller.

[0093] Summation

[0094] Any relative terms or terms of degree used herein, such as “substantially”, “essentially”, “generally”, “approximately”, and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass transitory signal or power fluctuations, ordinary manufacturing tolerance variations, incidental alignment variations, transient alignment or shape variations induced by thermal, rotational or vibrational operational conditions, and the like. Moreover, any relative terms or terms of degree used herein should be interpreted to encompass a range that expressly includes the designated quality, characteristic, parameter, or value, without variation, as if no qualifying relative term or term of degree were utilized in the given disclosure or recitation.

[0095] The word “comprise”, or variations such as “comprises” or “comprising” are used in an open-ended manner herein and should be interpreted to refer to the inclusion of a stated element, feature, or step, or group of elements, features, or steps, but not the exclusion of any other element, feature, or step, or group of elements, features, or steps. Unless further expressly qualified, use of the word “comprise” or variations thereof does not, alone, exclude the present additional, unrecited elements, steps, or groups of elements or steps. Additionally, unless further expressly qualified, the words “a” and “an” as used herein refer to one or more and do not limit the identified element, feature, step, or the like to one and only one. However, use of the words “a” and “an” herein should be interpreted in accordance with and subject to any applicable further limits expressly stated in the context of any particular instance of usage, without extending such context-specific limits to all other uses generally.

[0096] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. A method of discharging electrical power, the method comprising: rotating a fan with an electric motor to provide kinetic energy; opening a disconnect switch to disconnect an electrical power source from the electric motor; generating electrical power by rotating the electric motor using the kinetic energy; providing electrical power generated by the electric motor to a microcontroller; bringing the fan to a controlled stop; and dissipating electrical power from an inverter power module connected to the electric motor through the electric motor as heat.

2. The method of claim 1 and further comprising: receiving a safe state command with the microcontroller as an initial step of the method.

3. The method of claim 2 and further comprising: evaluating an elapsed time since the safe state command was received against a time limit with the microcontroller; and initiating the controlled stop of the fan prior to reaching the time limit.

4. The method of claim 1 and further comprising: rectifying the electrical power generated by the electric motor from high voltage AC power to high voltage DC power; and converting the high voltage DC power to lower voltage DC power.

5. The method of claim 4 and further comprising: after the step of opening the disconnect switch to disconnect the electrical power source from the electric motor, closing a low voltage power connection switch that is connected between the inverter power module and the microcontroller.

6. The method of claim 1 and further comprising; placing the microcontroller in a safe state mode.

7. The method of claim 1, wherein the step of dissipating electrical power from the inverter power module connected to the electric motor through the electric motor as heat involves dissipating electrical power through a winding of the electric motor.

8. The method of claim 7, wherein the step of dissipating electrical power from the inverter power module connected to the electric motor through the electric motor as heat further involves dissipating electrical power through a brake resistor of the electric motor.

9. The method of claim 1 and further comprising; dissipating electrical power from an external electric device through the electric motor as heat, wherein the step of opening the disconnect switch to disconnect the electrical power source from the electric motor occurs after the step of dissipating electrical power from the external electric device through the electric motor as heat.

10. The method of claim 9 and further comprising: opening an external switch between the electrical power source and a bus, wherein the bus is connected between the electrical power source and both the electric motor and the external electrical device.

11. A high voltage system discharge apparatus comprising: an inverter including: a microcontroller; a power module including inverter circuitry with a plurality of electronic switching devices and rectifier circuitry, wherein the power module is controlled by the microcontroller; a high voltage disconnect switch connected to the power module; a DC / DC converter electrically connected to the power module; andan internal low voltage power connection connected between the DC / DC converter and the microcontroller; a motor having at least one winding, wherein the motor is electrically connected to the power module; a mechanical output device operably connected to the motor, wherein the mechanical output device is rotatable; and instructions stored in a non-transitory medium and executable by the microcontroller to cause the inverter to: control operation of the motor to rotate the mechanical output device to provide kinetic energy; control operation of the motor to generate electrical power using the kinetic energy; utilize electrical power generated by the motor to operate the microcontroller; control operation of the motor to bring the mechanical output device to a controlled stop; and control operation of the motor to dissipate electrical power from the power module through the motor as heat.

12. The high voltage system discharge apparatus of claim 11, wherein the mechanical output device is a fan.

13. The high voltage system discharge apparatus of claim 11 , wherein the internal low voltage power connection is either a diode or a switch controlled by the microcontroller.

14. The high voltage system discharge apparatus of claim 11, wherein the inverter further comprises: a diode arranged to prevent low voltage electrical power from passing out of the inverter to an external low voltage power source.

15. The high voltage system discharge apparatus of claim 11, wherein the motor further comprises a brake resistor, wherein the instructions stored in the non-transitory medium andexecutable by the microcontroller further cause the inverter to control operation of the motor to dissipate additional electrical power through the brake resistor.

16. The high voltage system discharge apparatus of claim 11, wherein the inverter further comprises: an enclosure.

17. A vehicle comprising: the high voltage system discharge apparatus of claim 11; a high voltage power supply; an external disconnect switch; a high voltage bus, wherein the high voltage disconnect switch is connected between the high voltage bus and the power module, and wherein the external disconnect switch is connected between the high voltage power supply and the high voltage bus; an external device electrically connected to the high voltage bus; an electronic control unit; and a communications bus connected to the microcontroller and the electronic control unit.

18. The vehicle of claim 17 and further comprising: a crash sensor configured to send a safe state command signal to the microcontroller.

19. The vehicle of claim 17, wherein the instructions stored in the non-transitory medium and executable by the microcontroller further cause the inverter to control operation of the motor to dissipate electrical power from the external electric device through the motor as heat.

20. The vehicle of claim 17, wherein the electronic control unit is configured to open the external disconnect switch between the high voltage power supply and the high voltage bus following issuance of a safe state command signal.

21. The vehicle of claim 17, wherein the instructions stored in the non-transitory medium and executable by the microcontroller further cause the inverter to evaluate an elapsed time since a safe state command was issued against a time limit using the microcontroller.

22. A method of discharging high voltage electrical power, the method comprising: receiving a safe state command with a microcontroller; rotating a mechanical output device with an electric machine to provide kinetic energy, wherein the electric machine is electrically driven by a power module having inverter circuitry that includes a plurality of electronic switching devices; opening a disconnect switch connected between a bus and the power module, wherein opening the disconnect switch disconnects the electric machine from electrical power available from the bus; generating high voltage electrical power by rotating the electric machine using the kinetic energy; rectifying the high voltage electrical power generated by the electric machine from high voltage AC power to high voltage DC power; converting the high voltage DC power to lower voltage DC power; providing the lower voltage DC power to the microcontroller; bringing the mechanical output device to a controlled stop by a time limit; and dissipating electrical power from the power module through a winding of the electric machine as heat.

23. The method of claim 22 and further comprising: evaluating an elapsed time since the safe state command was received against a time limit using the microcontroller.

24. The method of claim 22 and further comprising: placing the microcontroller in a safe state mode.

25. The method of claim 22 and further comprising: dissipating electrical power through a brake resistor of the electric machine.

26. The method of claim 22 and further comprising: opening an external switch between an electrical power source and the bus.

27. The method of claim 26 and further comprising: dissipating electrical power from an external electric device through the electric machine as heat, wherein the step of opening the external switch between the electrical power source and the bus occurs before the step of dissipating electrical power from the external electric device through the electric machine as heat.

28. The method of claim 22 and further comprising: after the step of opening the disconnect switch connected between the bus and the power module, closing a low voltage power connection switch that is connected between the power module and the microcontroller.

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