CN106877279A - Redundant circuit disconnect for electric vehicles - Google Patents

Abstract

Systems and methods for redundant circuit disconnection in electric vehicles are disclosed. The system may include a resistive metal fuse for the battery or otherwise connected in circuit, an inductor comprising at least one turn of wire coil about a longitudinal axis, and an AC power source configured to provide an alternating current across the inductor. The resistive metal fuse may be disposed within the inductor along the longitudinal axis, and the AC power source may be configured to cause the inductor to induce in the resistive metal fuse sufficient to melt or vaporize An eddy current of the magnitude of at least a portion of said resistive metal fuse disposed therein.

Description

Redundant circuit disconnection for electric vehicles

technical field

The present disclosure relates to vehicle battery systems, and more particularly to systems and methods for providing redundant battery disconnect protection through inductive thermal fuses.

Background technique

Electric vehicle batteries are often protected by magnetic contactors that allow disconnection of the battery circuit if necessary. In some battery systems, two contactors may be provided in series to provide redundancy, allowing the circuit to be broken if one contactor is welded or otherwise stuck in the on position.

Contents of the invention

The systems and methods of the present disclosure each have several innovative aspects, no single one of which is solely responsible for its desirable attributes. Without limitation in scope as expressed by the appended claims, the more prominent features will now be discussed more briefly.

In one embodiment, a redundant disconnect system for use in an electrical circuit is described. The system includes a switch. The system may further include a resistive metal fuse connected in series with the switch within the circuit and an inductor comprising at least one turn of wire around a longitudinal axis. The system may also include an AC power source configured to provide an alternating current across the inductor. The resistive metal fuse may be disposed within the inductor along the longitudinal axis, and the AC power source may be configured to cause the inductor to induce a temperature sufficient to melt or vaporize within the resistive metal fuse. At least a portion of the resistive metal fuse is sized for eddy currents.

In another embodiment, a redundant disconnect method applied in an electric circuit is described. The method may include: providing a switch connected within the circuit; providing a resistive metal fuse connected in series with the switch within the circuit; and providing an inductor comprising at least one turn of wire around a longitudinal axis. The method may further include: instructing the switch to open the circuit; detecting a failure of the switch to open the circuit; and applying an alternating current to the inductor. The alternating current applied to the inductor may induce an eddy current in the resistive metal fuse of a magnitude sufficient to melt or vaporize at least a portion of the resistive metal fuse.

In another embodiment, a vehicle with redundant battery protection is described. The vehicle includes at least one electrical circuit, at least one battery connected within the circuit, and a switch connected in series with the battery within the circuit. The vehicle may also include a resistive metal fuse connected in series with the battery and the switch within the circuit, an inductor comprising at least one turn of wire around a longitudinal axis, and configured to connect across the inductor An AC power source that supplies alternating current. The resistive metal fuse may be disposed within the inductor along the longitudinal axis, and the AC power source may be configured to cause the inductor to induce a temperature sufficient to melt or vaporize within the resistive metal fuse. At least a portion of the resistive metal fuse is sized for eddy currents.

Description of drawings

The above-described aspects of the technology, as well as other features, aspects, and advantages, will now be described with reference to the accompanying drawings in conjunction with various implementations. The illustrated implementations are examples only and are not intended to be limiting. Throughout the drawings, similar symbols typically identify similar components, unless context dictates otherwise.

FIG. 1 is a circuit diagram depicting a redundant disconnect system in a simple battery circuit according to an exemplary embodiment.

2 is a circuit diagram depicting an example configuration of multiple redundant disconnect systems in a multi-string electric vehicle battery circuit according to an exemplary embodiment.

3 depicts a detailed view of an induction heated fusible fuse device for a redundant circuit disconnect system according to an exemplary embodiment.

FIG. 4 is a flowchart depicting a method for redundant disconnection of a circuit according to an exemplary embodiment.

detailed description

The following description is directed to certain implementations for the purpose of describing the innovative aspects of the present disclosure. However, those skilled in the art will readily recognize that the teachings herein can be applied in many different ways. The described implementations can be implemented in any circuit. In some implementations, the words "battery" or "batteries" will be used to describe certain elements of the embodiments described herein. It should be noted that "battery" does not necessarily refer to only a single battery cell. Rather, any element described as a "battery" or shown in the drawings as a single battery in a circuit diagram may equivalently be composed of any greater number of individual battery cells without departing from the disclosed The spirit or scope of systems and methods.

FIG. 1 is a circuit diagram depicting a redundant disconnect device 100 in a simple battery circuit 102 according to an exemplary embodiment. In some embodiments, the electrical circuit 102 may include at least one battery 104 and a main disconnect 106, such as a magnetic contactor or any other type of electrical switch capable of breaking and closing an electrical circuit. In some embodiments, the battery circuit may further include an electric motor 108 . The motor 108 may comprise a DC motor, a combination AC motor and power inverter, or any other type of motor or motor system capable of drawing power from a DC circuit.

Contactors or other electrical switches 106 are susceptible to occasional failures, such as welding or other mechanical failures. Such a fault may prevent the switch 106 from being turned on or it may prevent the switch 106 from being turned off. Redundant disconnect device 100 may be capable of interrupting circuit 102 when switch 106 is on and a mechanical failure prevents opening switch 106 .

The redundant disconnect device 100 described in more detail below with reference to FIG. 3 may include a resistive metal fuse 110 . The fuse 100 may be disposed within a wire coil 112 which may be electrically and/or thermally isolated from the fuse 110 and the DC circuit 102 . As described below, the fuse may have a rating sufficient to carry at least the DC circuit current normally flowing through the fuse 110 during normal operation of the DC battery circuit 102 . The two ends of the wire coil 112 may be connected across an AC power source 114 configured to generate an alternating current in the wire of the coil 112 . As will be described below, the AC power source may be capable of generating an alternating current having a magnitude sufficient to induce eddy currents sufficient to melt or vaporize the fuse 110 .

In some embodiments, the fuse 110 may be connected in series with the at least one battery 104 within the DC circuit 102 such that there is no closed circuit path within the at least one battery 104 that bypasses the fuse 110 . Thus, after the AC power source 114 is activated and the fuse 110 has melted or vaporized, the DC battery circuit 102 is disconnected because current can no longer flow through the fuse 110 .

FIG. 2 is a circuit diagram depicting an example configuration of multiple redundant disconnect systems 202 in a multi-string electric vehicle battery circuit 200 according to an example embodiment. The multi-string electric vehicle battery circuit 200 may include at least one electric motor 204 . The motor 204 may be any type of motor capable of drawing power from a DC battery circuit, such as a DC motor or a combination of an AC motor and a power inverter. In some embodiments, electric motor 204 may include one or more electric motors of an electric vehicle powertrain or may include an electric motor configured for non-powertrain functions.

In various embodiments, battery system 200 may include a single battery 206 or multiple batteries 206 . In some embodiments, six or more batteries 206 may be included in the battery circuit 200 to provide substantial power to the electric motor 204 or in the event one or more batteries 206 are damaged, leaking, malfunctioning, or otherwise unable to safely provide power to the electric motor 204 . Provides redundancy where power is available. In some embodiments, multiple batteries 206 may be arranged in individually switchable strings 208 . Each battery string 208 may include at least one battery 206 and at least one switch 210 for removing the at least one battery 206 from current in the battery circuit. Switch 210 may be any device capable of breaking a circuit. For example, in some embodiments, switch 210 may be a magnetic contactor or a mechanically operated switch. In some embodiments, any number of switches 210 may be actuated automatically by a battery management system, string management system, or other type of computing device configured to control or protect battery circuit 200 .

In a complex battery circuit 200 comprising multiple strings 208 of batteries 206, failure of switch 201 to operate as desired can result in a serious risk of damage. This risk is particularly high when battery 206 is a high voltage battery capable of powering an electric vehicle powertrain. Engaging the battery strings 208 with the main battery circuit 200 in the wrong order, engaging a string 208 including a damaged or faulty battery 206, or allowing the battery strings 208 to remain connected within the battery circuit 200 when they should be disconnected for any safety or performance-related reason Damage to the electric motor 204 or other batteries 206 may result. This condition can also cause damage to other components of the electric vehicle and can even cause bodily injury to occupants of the vehicle or people nearby, as a severe battery failure can lead to a fire or explosion.

The risk associated with the failure of the switch 210 in the battery string 208 can be significantly reduced by including a redundant disconnect device 202 connected in series with the switch 210 and the battery 206 in each string 208 . Various types of redundant disconnect devices 202 may be used. In some embodiments, redundant disconnect device 202 may be a contactor. However, the additional contactors can be very large and add cost, and if the vehicle includes multiple battery circuits, providing two contactors in the battery circuits can add significant weight and cost to the vehicle. Additionally, there is relatively little benefit in including a second contactor in the battery circuit because the second contactor is also as susceptible to welding or other failure as the first contactor in the circuit.

In some embodiments, redundant disconnect device 202 may be an inductively blowable fuse device as described above with reference to FIG. 1 and below with reference to FIG. 3 . If the redundant disconnect device 202 is an inductively blowable fuse, the required AC current can come from a number of possible sources. In some embodiments, each disconnect device 202 may have its own AC power source. In some embodiments, disconnect device 202 may draw AC power from a single source. The single AC power source may be an inverter providing AC current to the electric motor 204, an inverter coupled to other high voltage battery strings 208, an inverter coupled to a separate lower voltage power source for other vehicle systems, configured to use AC induction motors for regenerative braking or any other AC power source that may be located within an electric vehicle.

FIG. 3 depicts a cross-sectional view of an induction heated blowable fuse device 300 according to an exemplary embodiment. In some embodiments, device 300 may include a central resistive metal fuse 302 . The central resistive metal fuse 302 may be connected within the battery circuit such that current may flow through the resistive metal fuse 302 during normal operation of the battery circuit. Accordingly, the resistive metal fuse 302 should have a current rating high enough to carry at least the normal current 302 that occurs during normal operation of the battery circuit.

Resistive metal fuse 302 may be arranged along longitudinal axis 304 of wire coil 306 . In some embodiments, the coil of wire 306 may comprise a single turn of wire. In other embodiments, the coil of wire 306 may include two or more turns, up to tens, hundreds, or thousands of turns. Coil 306 may include wires made of any metal capable of conducting electricity. In some embodiments, coil 306 may be made of copper wire. In some embodiments, the coil 306 may be wound around a solid insulator 308 made of an electrically insulating material. For example, in some embodiments, insulator 308 may be made of ceramic. In some embodiments, insulator 308 may comprise plastic, glass, or any other electrically insulating material. In some embodiments, insulator 308 may be made of a material that is both electrically and thermally insulating. In some embodiments, insulator 308 may be in the form of a hollow tube surrounding resistive metal fuse 302 . An insulator 308 may surround the resistive metal fuse 302 . In other embodiments, an air gap 310 may be disposed between the insulator 308 and the resistive metal fuse 302 . The air gap 310 may improve the functionality of the device 300 by allowing space to dissipate material released from melting or vaporizing at least a portion of the resistive metal fuse 302 .

When it is desired to blow fuse 302 , an alternating current may be applied to wire coil 306 by AC power source 312 . When a varying electrical current, such as a standard sinusoidal alternating current, flows through a turn of wire or a coil of multiple turns of wire, a magnetic field is generated that flows through the turn of wire. Where the wire coil 306 consists of multiple turns of wire, the current within each turn adds to the total magnetic field generated in the coil 306 . Because the alternating current varies sinusoidally in magnitude and direction, the magnetic field will not be constant but will also vary sinusoidally over time. Thus, if resistive metal fuse 302 is disposed within coil of wire 306 along its longitudinal axis 304 , fuse 302 will be exposed to a magnetic field oriented along longitudinal axis 304 . However, the magnitude of this magnetic field will vary constantly.

Typically, subjecting a conductive material to a time-varying magnetic field induces eddy currents in the conductive material. Eddy currents occur naturally due to the electric field associated with the time-varying magnetic field within the inductor. Eddy currents flow in planes perpendicular to the magnetic field and generally act like closed current loops in those perpendicular planes. Thus, when resistive metal fuse 302 is exposed to a sinusoidal time-varying magnetic field along longitudinal axis 304 , eddy currents 314 will flow circumferentially within fuse 302 in a plane perpendicular to longitudinal axis 304 .

The magnitude of the induced eddy current 314 is directly related to the magnitude of the time-varying magnetic field. The magnitude of the time-varying magnetic field is in turn directly related to the magnitude of the alternating current in the induction coil 306 . Accordingly, high magnitude alternating current in induction coil 306 can induce sufficient current in resistive metal fuse 302 to generate sufficient resistive heating within fuse 302 . Resistive heating can cause fuse 302 to melt or vaporize in a manner similar to conventional fuses, thereby interrupting the battery circuit.

In some embodiments, resistive metal fuse 302 may be part of a battery circuit of an electric vehicle. In some embodiments, the battery circuit may be a high voltage battery circuit configured to provide power to a vehicle powertrain. In high current applications such as electric vehicle powertrains, the fuse 302 should preferably have a current rating sufficient to carry the current required for powertrain operation. In some embodiments, operation of the powertrain may require up to hundreds of amperes of current through the battery circuit. In an embodiment in which the fuse 302 has a rated current in the range of 300 amps, the induced eddy current 314 may have a root mean square (RMS) value in the range of 500 to 600 amps resulting in about 0.1 to 100 msec. necessary to melt or vaporize. Various embodiments of induction coil 306 and AC power source 312 can generate eddy currents of this magnitude. For example, a coil comprising 1000 turns of 30 gauge wire can generate eddy currents of the necessary magnitude when the current in the induction coil has an RMS value of 25 mA at a frequency of 150 kHz. Accordingly, the AC power source 312 that provides AC current to the wire coil 306 may be sufficiently powerful to provide the desired magnitude of AC current.

FIG. 4 is a flowchart depicting a method 400 for redundant disconnection of a circuit according to an exemplary embodiment. In some embodiments, method 400 may be used by the inductively blowable fuse devices described above with reference to FIGS. 1 and 3 . In some embodiments, method 400 may be applied to simple or complex battery circuits as described above with reference to FIGS. 2 and 3 .

Method 400 may begin at block 405, where a switch in an electrical circuit is commanded to open at least a portion of the electrical circuit. In some embodiments, the associated switch may be configured to stop all current flow in the circuit when opened. In some embodiments, the switch may be a branch of a parallel circuit such that opening it stops current flow through one branch of the circuit while allowing current to continue or begin to flow through the other parallel branch of the circuit. In the case of a multi-string electric vehicle battery circuit, the command to disconnect part of the circuit may be given for a variety of reasons, including the detection of a battery failure in one string, routine activation or deactivation of a battery string, or the need for Any other reason for cutting out a single cell in the circuit current.

After the command to open the switch is given, the method 400 may continue to block 410 or block 425 . If the switch opens as commanded, method 400 may continue to block 425, where the circuit or portion of a circuit is opened, current flow ceases, and method 400 may end. However, if the switch does not open as commanded, method 400 may continue to block 410 where a fault may be detected. An opening failure of the switch in response to an opening command can be detected in various ways. In some embodiments, a current detector may measure the continuous current flowing through the string, either directly or through a shunt, to determine that the circuit has not been broken by the switch. In some embodiments, the sensor may be capable of detecting the physical position of the switch in the on position or otherwise determining that the switch is still on after receiving the off command.

After the failure of the switch to open the circuit is detected, the method 400 may proceed to block 415 where an AC current is applied to the induction coil to induce eddy currents in the resistive metal fuses within the circuit. In some embodiments, the resistive metal fuse and induction coil may be configured as described above with reference to FIGS. 1 and 3 . The magnitude of the AC current may be determined based at least in part on the magnitude of the DC current that has flowed through the fuse and the current rating of the fuse. The AC current can be determined to induce eddy currents within the fuse sufficient to exceed the rated current of the fuse.

After applying the AC current to the induction coil, the method may continue to block 420 where at least a portion of the resistive metal fuse is melted and/or vaporized. Melting and/or vaporizing at least a portion of the resistive metal fuse may occur shortly after application of the AC current due to the immediate induction of eddy currents exceeding the rated current of the fuse. Melting and/or vaporization may occur due to resistive heating caused by eddy currents flowing circumferentially within the metal of the fuse, as described above with reference to FIG. 3 . Because eddy currents flow circumferentially, no additional current is added to the existing DC current within the fuse. When a portion of the fuse melts and/or vaporizes due to induction heating, the molten and/or vaporized metal can move. For example, molten metal may flow along fuses and/or other circuits or fall into the air gap due to gravity. In some embodiments, when an air gap exists between the fuse and the surrounding insulator, the vaporized metal may be pushed outward across the air gap from its original position within the fuse and may collect or may deposit on the inner surface of the surrounding insulator superior. Additionally, a portion of the vaporized fuse metal can be vented from the entire fuse assembly.

After at least a portion of the resistive metal fuse is melted and/or vaporized, method 400 may proceed to block 425 where the circuit is opened and the method ends. Here, the result is essentially the same if the switch had been opened as commanded in block 405 . Melted and/or vaporized portions of the fuse may have changed the geometry of the fuse creating a gap within the circuit. Therefore, the circuit will open and current will stop flowing through that part of the circuit that contains the fuse. Repair work including replacing or repairing blown fuses can be done later. In some embodiments, fuse repair work may be performed in addition to or concurrently with repairing the battery or battery string, which in some embodiments may address battery damage or malfunctions requiring blown fuses.

It should be noted that these examples are described as procedures. Although these operations may be described as a sequential process, many of these operations may be performed in parallel or concurrently, and the process may be repeated. Also, the order of these operations can be rearranged. A process ends when its operations are complete. A procedure may correspond to a method, function, procedure, subroutine, subroutine, and so on. When a procedure corresponds to a software function, its end corresponds to the return of the function to the calling or main function.

The preceding description of the disclosed implementations is provided to enable any person skilled in the art to make or use the processes and systems disclosed herein. Various modifications to these implementations will be readily apparent to those skilled in the art, and the generic concepts described herein can be applied to other implementations without departing from the spirit or scope of the processes and systems disclosed herein. Thus, the processes and systems disclosed herein are not intended to be limited to the implementations shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (20)

1. A redundant disconnection system applied in a circuit, said system comprising: switch; a resistive metal fuse connected in series with the switch within the circuit; Inductors comprising at least one coil of wire around a longitudinal axis; and an AC power source configured to provide an alternating current across the inductor; wherein the resistive metal fuse is disposed within the inductor along the longitudinal axis, and the AC power source is configured to cause the inductor to induce in the resistive metal fuse sufficient to melt or vaporize An eddy current of the magnitude of at least a portion of said resistive metal fuse disposed therein. 2. The redundant disconnect system of claim 1, wherein the switch is a magnetic contactor. 3. The redundant disconnect system of claim 1, further comprising a layer of electrically insulating material disposed between the resistive metal fuse and the inductor. 4. The redundant disconnect system of claim 3, further comprising an air gap disposed between the resistive metal fuse and the layer of electrically insulating material. 5. The redundant disconnect system of claim 1, wherein the coil comprises multiple turns of wire. 6. The redundant disconnect system of claim 1, further comprising a battery connected in series with said switch and said resistive metal fuse within said circuit. 7. The redundant disconnect system of claim 6, wherein the system further comprises a plurality of individually switchable parallel battery strings, and wherein each battery string comprises: Battery; a switch connected in series with the battery; a resistive metal fuse connected in series with the switch and the battery; Inductors comprising at least one coil of wire around a longitudinal axis; and an AC power source configured to provide an alternating current across the inductor; wherein the resistive metal fuse is disposed within the inductor along the longitudinal axis, and the AC power source is configured to cause the inductor to induce in the resistive metal fuse sufficient to melt or vaporize An eddy current of the magnitude of at least a portion of said resistive metal fuse disposed therein. 8. The redundant disconnect system of claim 7, wherein the switch is a magnetic contactor. 9. A redundant disconnection method applied in a circuit, said method comprising: providing a switch connected within said circuit; providing a resistive metal fuse connected in series with the switch within the circuit; providing an inductor comprising at least one turn of wire coiled around said resistive metal fuse; and instructing the switch to open the circuit; detecting a failure of the switch to open the circuit; and applying an alternating current to the inductor; Wherein, the alternating current in the inductor induces an eddy current in the resistive metal fuse of a magnitude sufficient to melt or vaporize at least a portion of the resistive metal fuse. 10. The redundant disconnect method of claim 9, wherein the switch is a magnetic contactor. 11. The redundant disconnection method of claim 9, wherein the coil comprises multiple turns of wire. 12. The redundant disconnect method of claim 9, further comprising providing a battery connected in series with said switch and said resistive metal fuse within said circuit. 13. The redundant disconnect method of claim 12, wherein said step of instructing said switch to disconnect said circuit is performed in response to a failure of said battery. 14. A vehicle with redundant battery protection, the vehicle comprising: at least one circuit; at least one battery connected within said circuit; a switch connected in series with the battery within the circuit; a resistive metal fuse connected in series with the battery and the switch within the circuit; Inductors comprising at least one coil of wire around a longitudinal axis; and an AC power source configured to provide an alternating current across the inductor; wherein the resistive metal fuse is disposed within the inductor along the longitudinal axis, and the AC power source is configured to cause the inductor to induce in the resistive metal fuse sufficient to melt or vaporize An eddy current of the magnitude of at least a portion of said resistive metal fuse disposed therein. 15. The vehicle of claim 14, wherein the switch is a magnetic contactor. 16. The vehicle of claim 14, further comprising a layer of electrically insulating material disposed between the resistive metal fuse and the inductor. 17. The vehicle of claim 14, further comprising an air gap disposed between the resistive metal fuse and the layer of electrically insulating material. 18. The vehicle of claim 14, wherein the coil comprises multiple turns of wire. 19. The vehicle of claim 14, wherein the vehicle further comprises a plurality of individually switchable parallel battery strings, and wherein each battery string comprises: Battery; a switch connected in series with the battery; a resistive metal fuse connected in series with the switch and the battery; Inductors comprising at least one coil of wire around a longitudinal axis; and an AC power source configured to provide an alternating current across the inductor; wherein the resistive metal fuse is disposed within the inductor along the longitudinal axis, and the AC power source is configured to cause the inductor to induce in the resistive metal fuse sufficient to melt or vaporize An eddy current of the magnitude of at least a portion of said resistive metal fuse disposed therein. 20. The vehicle of claim 19, wherein the switch is a magnetic contactor.