GB2593917A

GB2593917A - An electric power supply disconnecting device and a method for disconnecting an electric power supply from a load in a vehicle

Info

Publication number: GB2593917A
Application number: GB2005262.7A
Authority: GB
Inventors: Dixit Rishabh; Kulkarni Pravin
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2020-04-09
Filing date: 2020-04-09
Publication date: 2021-10-13
Anticipated expiration: 2040-04-09
Also published as: GB202005262D0; GB2593917B

Abstract

An electric power supply disconnecting device comprising a pyro mechanical separation device 16; a Rogowski coil 10 for detecting an event on a current line 12 connected to the pyromechanical separation device and for generating a voltage pulse in case of a detected event; circuitry 14 for processing the voltage pulse and triggering the pyrotechnical separation device 16 depending on the processing. The circuitry may comprise a comparator means (fig.2, 20) for comparing a Rogowski coil output signal with a reference signal set to a value of a fault current representing an event on the current line; and a switching means, controlled by a comparator means output signal, connected between a ground contact of the pyromechanical separation device and a predefined voltage potential. The circuitry may comprise a digital circuit (fig.3, 28) or a delay circuit (fig.2, 24) adapted to delay the output signal of the comparator means by a time span. A method providing said disconnecting device in a current line used to disconnect the power supply from a load in a vehicle, particularly an electric vehicle.

Description

AN ELECTRIC POWER SUPPLY DISCONNECTING DEVICE AND A METHOD FOR DISCONNECTING AN ELECTRIC POWER SUPPLY FROM A LOAD IN A

VEHICLE

TECHNICAL FIELD

This specification relates to an electric power supply disconnecting device and a method for disconnecting an electric power supply from a load in a vehicle, particularly an electric vehicle.

BACKGROUND

Pyromechanical separation devices or pyrotechnical safety switches (PSSs) are for example described in EP 1 447 640 Al US 2007/0034491 Al, and US 2019/0108957 Al A PSS is a device that utilizes a small pyrotechnical charge in order to either couple or decouple a conductive wire. A PSS is triggered with a control signal having an electric current high enough to cause the PSS's pyrotechnical charge to explode. The explosion then propels a non-conductive guillotine head through the PSS's conductor, thus breaking a circuit.

SUMMARY

This specification describes an electric power supply disconnecting device and a method for disconnecting an electric power supply from a load in a vehicle, particularly an electric vehicle (EV).

An aspect of this disclosure relates to an electric power supply disconnecting device comprising a pyromechanical separation device, at least one Rogowski coil provided and adapted for detecting an event on a current line connected to the pyromechanical separation device and for generating a voltage pulse in case of a detected event, and circuitry for processing the voltage pulse generated by the at least one Rogowski coil and triggering the pyromechanical separation device depending on the processing. This device is particularly suitable to interrupt a direct current (DC) line since an event such as a sudden change of the direct current on the line, for example cause by a short circuit of a load, may incur a voltage pulse at the output of a Rogowski coil arranged around the direct current line, which may then be used to trigger a pyromechanical separation device, particularly to cause an explosion of a pyrotechnical charge of the pyromechanical separation device Interrupting a DC line is usually more difficult to interrupt an alternating current (AC) line since the DC current has zero crossing, which could trigger an interruption device. Particularly, a risk for arcing has to be carefully considered when interrupting DC lines. For example, a DC through an inductor is particularly problematic regarding generating arcs since an inductor will still drive a current even if the power supply is cut off due to its inherent trait of being slow to adapt chances in current. This can be avoided with the disclosed device since no inductor is required, and the Rogowski coil can generate a voltage pulse for triggering the pyromechanical separation device. A further advantage over existing pyromechanical separation devices can be seen in that no external control or trigger signal for example from separate electronics is required for triggering the pyromechanical separation devices, but instead the triggering is independent from other electronics, which may be particularly useful for an application in an EV to separate a load from a battery. The electric power supply disconnecting device may be for example implemented as integrated module, which is applicable for different application, particularly in an EV.

The module may comprise only two external contacts for a current line, and no further contacts are required due to the device integration.

In an embodiment, the circuitry may comprise a wiring of an output of the at least one Rogowski coil with an activation input of the pyromechanical separation device. This allows a technical less complex implementation, which does not require an external power supply, and the design is entirely passive. For this implementation, the voltage and current required for triggering the pyromechanical separation device may determine the parameters of the at least one Rogowski coil. For example, for an application in an EV, the minor and major radius of a Rogowski coil may be predefined due to the size of the cables used in the EV, leaving the number of the coil's windings the variable available to obtain the required voltage. The number of windings, together with the minor radius of the coil determine the length of the wire used for the coil. This length in combination with the thickness of the wire and wire's material, for example copper; define the wire's resistance. Thus, the number of windings of the coil determine the voltage, and the coil's wire length determine the electrical resistance. From both, the electric current available for triggering the pyromechanical separation device can be determined.

In an alternative embodiment; the circuitry may comprise comparator means for comparing an output signal of the at least one Rogowski coil with a reference signal and switching means controlled by an output signal of the comparator means, wherein the switching means are connected between a ground contact of the pyromechanical separation device and a predefined voltage potential; and wherein to the reference signal is set to a value representative of a fault current as event on the current line. Thus, the output signal of the at least one Rogowski coil is amplified with the circuitry in order to trigger the pyromechanical separation device. This may be helpful when the pyromechanical separation device requires a voltage and current for triggering, which cannot be obtained with a simple wiring of the output of a Rogowski is coil to the input of the pyromechanical separation device; for example since the length of the wire and its resistance is too high to generate an electric current sufficient for triggering, or the number of windings of the coil is limited and does not allow to generate a voltage high enough to trigger the pyromechanical switch.

The circuitry may comprise a delay circuit switched between an output of the comparator means and a control input of the switching means, wherein the delay circuit is provided and adapted to delay the output signal of the comparator means by a predefined time span. The predefined time span introduced by the delay circuit may be selected such that an event on the current line has a minimum duration. Thus, it may be ensured that spikes on the current line, which are not incurred by a severe event such as a short circuit in the load or a failure of the load, can trigger the pyromechanical separation deivce. Alternatively, the circuitry may comprise a digital circuit switched between an output of the comparator means and a control input of the switching means, wherein the digital circuit is provided and adapted to determine if the output signal of the comparator means generated for a predefined time span.

The switching means may comprise a transistor with a diode and resistor switched before its control contact to limit a control current feed to the control contact. A transistor as switch can be integrated with the electronics of the circuitry. The diode and resistor may ensure that the transistor control contact cannot be damaged by a high voltage pulse or current.

A further aspect of this disclosure relates to a method for disconnecting an electric power supply from a load in a vehicle, particularly an electric vehicle, comprising the following: providing an electric power supply disconnecting device as disclosed herein in a current line from a supply contact of the electric power supply to the load, arranging the at least one Rogowski coil around the current line, detecting events on the direct line by means of the at least one Regowski coil; and disconnecting the electric power supply from the load in the vehicle in case of a detected event on the current line with the electric power supply disconnecting device.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the

description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

Fig. 1 shows schematics a first embodiment of an electric power supply disconnecting device: Fig 2 shows schematics of a second embodiment of a circuitry of an electric power supply disconnecting device; and Fig. 3 shows schematics of a third embodiment of a circuitry of an electric power supply disconnecting device.

DETAILED DESCRIPTION

In the following; functionally similar or identical elements may have the same 25 reference numerals. .Absolute values are shown below by way of example only and should not be construed as limitino.

Fig. 1 shows an electric power supply disconnecting device comprising a Rogowski coil 10 arranged around a current line 12, particularly a DC current line, and a circuitry 14 connecting the output of the Rogowski coil 10 with the activation input of a pyromechanical separation device 16 switched into the current line 12.

The pyromechanical separation device 16 comprises two current line contacts 162 and 164 and is switched into the current line 12 by connecting two ends of the current line 12 to be connected with the contacts 162 and 164, respectively. Both contacts 162 and 164 are connected within the device 16 by means of a current rail 170.

An ignitor 168 is connected to the activation input 160 and integrated in the device 16. The ignitor 168 comprises a pyrotechnical charge, which can be caused to explode with an electric current flowing into the activation input 160. An explosion of the pyrotechnical charge of the ignitor 168 causes a cutter 172 with a non-conductive guillotine head 174 at its bottom to propel such that the guillotine head 174 cuts through the current rail 170 breaking the current line 12 and isolating the cut ends of the cut through contact rail 170.

The circuitry 14 is provided for triggering the pyrornechanical separation device 16. The Rogowski coil 10 may be dimensioned (windings, diameter of the coil, diameter of the windings; core material of coil, number of windings; diameter of the coil's wire; material of the coil's wire) such that a certain event on the current line, particularly a steep increase or decrease of the current flowing through the line 12, may cause an electric voltage pulse and an electric current pulse at the coil's output 100. The voltage pule and the current pulse are conducted via the wiring 18 to the activation input 160 and cause the ignitor 168 to explode to propel the cutter with the guillotine head 174 to break current rail 170 and interrupt the current line 12.

The entire design of the electric power supply disconnecting device shown in Fig. 1 may be integrated as a single module with only the two external contacts 162 and 164 accessible from outside of the module. For example, the module may be designed with two opening for inserting two ends of the current line 12; wherein the Rogowski coil 10 may be for example located at the contact 162 so that the introduced end of the current line is guided through the coil 10 in the contact 162. Thus, a compact module design may be obtained, which can be applied for example an EVs for interrupting the electrical energy supply from batteries to loads.

The device shown in Fig. 1 can quickly react on events on the current line 12. For example, when a load causes a short circuit such that the electric current flowing through line 12 steeply increases within some milliseconds, nearly immediately a respective voltage and current pulse may be generated at the output of the Rogowski coil 100 and supplied to the activation input 160 of the device 168 causing the ignitor 168 to explode and the cutter 172 to cut through the current rail 170 with the to guillotine head 174.

Fig. 2 and 3 show further circuitries 14' and 14" of an electric power supply disconnecting device, These circuitries 14', 14'1 are active implementations on contrast to the passive implementation of the circuitry 14 of Fig. 1. Active implementations mean that the output signal Vc of the Rogowski coil (not shown in Figs. 2 and 3) is processed with a comparator 20 to control the ignition of the ignitor via a transistor 22 serving as switch. Also, these circuitries 14' ,14" use an external supply voltage +E to trigger the pyrornechanical separation device 16.

The output signal Vc, a voltage pulse, of the Rogowski coil is supplied to one input of the comparator 20, which is supplied with an external power supply +E and F. In a simple implementation, the output 100 of the Rogowski coil 10 (Fig. 1) may be directly connected to the respective input of the comparator 20. A reference voltage Vref is generated from the power supply -E with a voltage divider comprising two resistors R1 and R2. The reference voltage Vref may correspond to the input voltage required at the activation input 160 for bringing the ignitor of the device 16 10 explosion for cutting the current line 12. In fact, the reference voltage Vref may be selected to be the threshold for triggering the device 16 For generating the respective reference voltage Vref, one of the resistors R1 or R2 may be selected, and the other one R2 Or R1 may be calculated to achieve the reference voltage.

A voltage divider can also be used to adapt the output voltage of the Rogowski coil to 30 the comparators input range. The voltage divider may be selected depending on the comparator's input voltage range arid the maximum output voltage generated by the Rogowski The comparator 20 generates an output signal depending on the input signal Vc from the Rogowski coil, which is supplied to a delay circuit 24 provided for delaying the inputted signal by a predefined time span. The predefined time span can be selected so that the short current pulses generated by the Rogowski coil are suppressed by the delay circuit 24, i.e. only current pulses and the respective voltage signal Vc exceeding the reference voltage Vref for at least the predefined time span are passed through by the delay circuit 24. Thus, short pulses generated by the to Rogowski coil, which might not be caused by a severe event on the current line, do not cause triggering of the device 15.

The delay circuit 24 outputs a current signal, which is supplied to the anode of a diode 26. The cathode of the diode 26 is connected via a resistor R3 to the base of a bipolar transistor 22 acting as a switch. The collector of the transistor 22 is connected to a ground contact 166 and its emitter to a predefined voltage potential, for example ground. The activation input 160 of the device 16 is connected to the external supply voltage E+.

Thus, when the input voltage Vc from the Rogowski coil exceeds for time span longer than the predefined time span from the delay circuit 24 the reference voltage Vref, an output current from the comparator 20 and delay circuit 24 flows through the diode 26 and the resistor R3 into the base of the transistor 22 as base current I base, which is then amplified to the collector current I collector = hi base with h designating the current amplification constant of the transistor 22. The collector current I collector flows from the activation input 180 to the ground contact 166 and via the collector and the emitter. The flowing current causes the ignitor of the device 16 to explode and to cut through the current rail within the device 16.

The circuitry 14" distinguishes from the circuitry 14' in that instead of the delay circuit 24 a digital circuit 28 is provided, which is supplied with a digital supply voltage Es. The digital circuit 28 may also implement a delay in that it determines if the output 30 signal of the comparator means 20 is generated for a predefined time span and only outputs a current signal when the comparator's output signal exceed the predefined time span.

Even if Rogowski coils are designed to work with alternating currents, they are used in embodiments of this disclosure to detect events on a direct current line, which particularly works well for detecting a change of an electric current during an abnormal condition such as a defects in a load causing a steep decrease or increase of the direct current. Since a Rogowski coil generates an output voltage which is proportional to the rate of change of the electric current flowing through the sensed current line, particularly steep changes of the sensed current even if it is a direct to current may cause significant voltage and current pulses at the output of a Rogowski coil, which can be used to trigger a pyromechanical separation device.

Claims

CLAIMS1. An electric power supply disconnecting device comprising * a pyromechanical separation device (16), S O at least one Rogowski coil (10) provided and adapted for detecting an event on a current line (12) connected to the pyromechanicai separation device (16) and for generating a voltage pulse in case of a detected event, and O circuitry (14, 14'; 14") for processing the voltage pulse generated by the at least one Rogowski coil (10) and triggering the pyrornechanical separation device (16) depending on the processing.
2. The device of claim 1, wherein the circuitry (14) comprises a wiring (18) of an output (100) of the at least one Rogowski coil (10) with an activation input (160) of the pyromechanical separation device (16).
3. The device of claim 1, wherein the circuitry (14'; 14") comprises comparator means (20) for comparing an output signal of the at least one Rogowski coil (10) with a reference signal and switching means (22) controlled by an output signal of the comparator means (20), wherein the switching means (22) are connected between a ground contact (166) of the pyrornechanical separation device (16) and a predefined voltage potential; and wherein the reference signal is set to a value representative of a fault current as event on the current line (12).
4 The device of claim 3, wherein the circuitry (14') comprises a delay circuit (24) switched between an output of the comparator means (20) and a control input of the switching means (22), wherein the delay circuit (24) is provided and adapted to delay the output signal of the comparator means (20) by a predefined time span.
5. The device of claim 3, wherein the circuitry (14") comprises a digital circuit (28) switched between an output of the comparator means (20) and a control input of the switching means (22), wherein the digital circuit (28) is provided and adapted to determine if the output signal of the comparator means (20) generated for a predefined time span.
6. The device of claim 3, 4 or 5, wherein the switching means (22) comprise a transistor with a diode (26) and resistor switched before its control contact to limit a control current feed to the control contact.
7. A method for disconnecting an electric power supply from a load in a vehicle, particularly an electric vehicle, comprising * providing an electric power supply disconnecting device of any preceding claim in a current line from a supply contact of the electric power supply to the load, * arranging the at least one Rogowski coil around the current line, * detecting events on the direct line by means of the at least one Rogow ski coil, and * disconnecting the electric power supply from the load in the vehicle in case of a detected event on the current line with the electric power supply disconnecting device.