DE102013104286A1 - Device and method for error arc detection - Google Patents

Abstract

There is provided an apparatus and method for detecting a fault arc using a current conductor (14) on a printed circuit board (PCB) (10) that provides power from an external power source to electrical components on the circuit board (10) by detecting a value which characterizes the rate of change of a current flowing through the current conductor (14). The apparatus and method may be used to detect both internal faults within the circuit board (10) and external faults outside the circuit board (10).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to those submitted on May 1, 2012 British Patent Application No. 12075347 the disclosure of which is incorporated herein by reference.

BACKGROUND TO THE INVENTION

Electrical circuits, such as those used in aircraft airborne systems, can use a relatively high voltage and are capable of delivering high current. Electrical faults, such as a fault arc, may occur therein, and these allow current to either flow through a conductive medium or to jump from one conductor to another via a nonconductive medium. The ability to detect such arcing faults is important because if they are not detected quickly, arcing faults can cause short circuits, malfunctions and other problems in the equipment powered by the electrical circuits.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a printed circuit board (also referred to as a printed circuit board (PCB)) includes a plurality of electrical components, a power conductor configured to be coupled to an external power supply external to the circuit board, and power to a plurality of electrical components, and a fault arc detector including a first air transformer disposed in the vicinity of the conductor to be coupled to a magnetic field generated by a current flowing through the conductor, and an output voltage, Vout, which is proportional to the rate of change of current, dI / dt, flowing through the conductor.

In another embodiment, a method for detecting an arc of error in a conductor on a printed circuit board includes detecting a value indicative of the rate of change of a current flowing through the conductor through an air transformer disposed on the circuit board and detecting a fault arc condition on the circuit Basis of the recorded value.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

1A and 1B show schematic representations of a printed circuit board (PCB) according to an embodiment of the invention.

2A shows a schematic representation of exemplary coils, which in the circuit board after 1 can be used.

2 B illustrates a simplified equivalent circuit diagram of 2A which allows an evaluation of the electromagnetic coupling parameters of the coil.

3 shows a schematic representation of an exemplary test circuit configuration according to an embodiment of the invention.

4A FIG. 12 illustrates a graphical representation of the fault due to a serial fault arc in FIG 3 illustrated circuit current, and 4B Figure 4 illustrates a graphical representation of the response of the amplified air coil output voltage.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention include the use of a coreless air transformer implemented on a printed circuit board (PCB) to detect the rapid rate of change of current (dI / dt), as a non-limiting example, in power distribution feeders in aircraft during serial and parallel fault arc events can be generated. Historical arc fault detection systems use hardware-based resistor-capacitor differentiators to determine the dI / dt of an output current sense circuit of a solid state power controller (SSPC). SSPCs are typically designed to read in about 600% of their rated currents to operate in the intended environment. Fault arcs at high voltages cause current disturbances on the order of only 5% of the rated current. Thus, it may be difficult to separate the fault arc fault from the general noise of the circuit. SSPCs often use shunt resistors as a means of measuring the current flowing through their terminals, and the shunt resistors are sized according to the above range, which means that the signal-to-noise ratio available for error arc detection is limited. Shunt resistors work well in low voltage applications, but lose their ability to distinguish the arc fault from the general noise of the circuit as the voltage increases. This difficulty can be illustrated by looking at specific examples.

In high voltage systems, the change in output current due to a serial fault arc is reduced according to the equation: deltaI = (VARC / VLINE) · ILOAD (1)

In the intended environment, a typical fault arc event results in a 20 volt signal. In a 28 volt DC system, the reduction of current during a 20 volt serial arc event gives the following relationship: delta I / ILOAD = 20/28 = 0.714 = 71.4%. However, in a 270 volt DC system, the current reduction during a similar 20 volt serial arc event gives the following relationship: delta I / ILOAD = 20/270 = 0.074 = 7.4%. In a typical current monitoring system within an SSPC, the measurement range usually ranges from 0% to 600% of the rated current. Typical loads applied to SSPCs are reduced to approximately 75% of the rated current value, so that the current change due to a serial fault arc assuming a line voltage of 270 volts DC is 7.4% of the 75% load current and only one Current value of 5.6% of the 600% full scale range. In contrast, the reduced load current in the 28 volt DC system is 53.6%, which is almost 10 times higher. The current value of 5.6% relative to the 600% range is only 0.93% of the full 600% scale range compared to 8.9% for the 28 volt system. Such a current change of 0.93% due to the serial fault arc is of the same order of magnitude as the accuracy of the current monitoring system within the SSPC. The change for the 28 volt system is an order of magnitude higher. Thus, although the arc fault event can be readily determined in a 28 volt DC system with the shunt resistor, this does not apply to the fault arc event in the 270 volt DC system.

The information required for the purposes of error arc detection is merely the AC content of the DC signal that provides power to the given load. Consequently, the DC content of the signal can be ignored, and the AC coupling characteristic of the transformer can be utilized. Due to the high DC current levels in the system, a typical core-containing current transformer can not be used due to the problem of core saturation. The coreless air-flow transformer implemented on a printed circuit board (PCB) does not saturate and thus solves this problem by ignoring any DC current components and supplying immediate dI / dt.

The invention provides a solution for determining arc fault events in high voltage environments. An embodiment of the invention is in 1A in the context of a printed circuit board (PCB) 10 Illustrates a circuit board 12 may contain a plurality of (not illustrated for clarity) electrical components, a conductor 14 and a fault arc detector 16 having. The board 12 may be made of any suitable material, such as a substrate or laminate, that is substantially non-thermally conductive. On the board 12 can be various components, including a memory, a microprocessor 11 and other electrical components 13 be mounted (eg resistors, diodes and capacitors).

The conductor 14 can be a busbar or any other type of conductor on the board 12 is provided. For illustrative purposes is the power conductor 14 as a bus bar. The conductor 14 can be configured to work with one for the circuit board 10 external power supply (not illustrated) to provide power to the multiple electrical components residing on the board 12 are located. The external voltage source may be at least 60 volts and is intended to have a higher voltage, including at least 220 volts.

The error arc detector 16 is illustrated as he has a first (ironless) air transformer 20 standing near the power conductor 14 is arranged, and a second air transformer 22 contains, in series with the first air transformer 20 switched or wired. The error arc detector 16 Further, a signal processing circuit or a fault arc detection circuit 21 contain. It is provided that the error arc detection circuit 21 an output to the microprocessor 11 can deliver and the microprocessor 11 can use the supplied signal to determine if there is a fault arc event. Alternatively, the error arc detection circuit 21 with the microprocessor 11 be coupled or part of the microprocessor 11 and may implement an algorithm to detect the incipient occurrence of a fault arc and determine an arc fault condition based on the detected value.

The first and the second air transformer 20 and 22 can be near the power conductor 14 be arranged to constructively positive and negative components of a magnetic field passing through the conductor 14 flowing current is generated, add. Both the first and the second air transformer 20 and 22 may contain a coil realized on or in the board. How clearer 1B can be seen is the first air transformer 20 illustrates how it contains a first coil through a winding 24 is formed, and the second air transformer 22 is illustrated as it contains a second coil through a winding 26 is formed, in the same direction as the winding 24 is wound. The first and the second air transformer 20 and 22 are wired antiphase in this manner to effect the constructive addition of the positive and negative components of the magnetic field during operation.

The windings 24 and 26 are illustrated as they trajectories on the board 12 in the form of a spiral, which is better in 2A is illustrated. The windings forming the ever decreasing rectangular spiral may be the sum of many geometrically similar rectangles of other dimensions, such as the coil 30 in 2 B illustrated. It is further contemplated that each coil may include multiple spirals at different levels in the board 12 the circuit board 10 can be arranged. It should be noted that in the figures described above, for purposes of simplicity, only a single coil is illustrated. The openings 32 show where multiple spirals on multiple levels of the circuit board 10 can be connected in series or wired.

The error arc detector 16 may further include a relay or an SSPC (not illustrated) that is incident on the fault arc detector 16 responds. The error arc detector 16 may include a circuit (not shown) that controls a relay or SSPC (not illustrated) to connect the power conductor 14 from the power supply when an arc fault is detected. Such a relay may include a circuit breaker or any other suitable mechanism for decoupling the conductor 14 from the power source when a fault arc occurs, and the particular manner in which the relay action is achieved does not affect the system described herein.

In operation, a fault arc in the conductor 14 through the error arc detector 16 be detected. The occurrence of the error arc is detected by the error arc detector 16 detects, preferably the rate of change of the electric current I in the conductor 14 as a function of time t, or dI / dt. During operation, the air transformer may be coupled to a magnetic field (as indicated by arrows B in FIG 1B illustrated) by a schematic arrow 28 illustrated current generated by the conductor 14 flows, and provide an output voltage, Vout, corresponding to the rate of change of the current, dI / dt, passing through the current conductor 14 flows, is proportional. In the illustrated embodiment, the voltage across the first and second air transformers 20 and 22 Be vout. The error arc detector 16 can receive Vout and determine therefrom a presence or the presence of a fault arc. In particular, the error arc detector can 16 capture a value representing the rate of change of the current conductor 14 indicates a flowing current and, based on the detected value, detects a fault arc condition. The determination of an error arc may be made based on whether the detected value exceeds a maximum permissible change speed value. It will be understood that such a determination can be easily modified to satisfy a positive / negative comparison or a true / false comparison. For example, a "less than threshold" comparison can be easily satisfied by using a "greater than" test when the data is numerically inverted. The permissible maximum rate of change value can be determined experimentally.

worin Vout = Spannung über den beiden in Reihe geschalteten Spulen;
dI/dt = Änderungsgeschwindigkeit des Stroms durch die Stromschiene;
K = die Anzahl von Spulen;
N = die Anzahl der Windungen;
a = Abstand von dem Mittelpunkt der Stromschiene zu dem Rand der Spule;
w = Weite der Spule;
l = Länge der Spule; und
s = Abstand zwischen Windungen in jeder Spule. To detect a fault arc, the fault arc detector detects 16 the value of the first and second air transformers 20 and 22 to constructively add positive and negative components of a magnetic field through the current conductor 14 flowing electricity is generated. The transfer function can be derived under the given parameters between the busbar current differential dI / dt and the coil output voltage Vout. The coil voltage Vcoil can be calculated using the equations:

where Vout = voltage across the two series-connected coils;
dI / dt = rate of change of the current through the bus bar;
K = the number of coils;
N = the number of turns;
a = distance from the center of the bus bar to the edge of the coil;
w = width of the coil;
l = length of the coil; and
s = distance between turns in each coil.

For the exemplary dual coil embodiment, five turns as shown in FIGS 1A and 1B is illustrated, the series can be evaluated as follows:

The voltage signal is indicative of the rate of change of the current over time, and the error arc detector 16 In this way, it can determine whether the rate of change is above an allowed maximum rate of change.

The more turns per coil and the more layers or planes per coil are used, the greater the coupling between the dI / dt and the coil output voltage Vout. The relationship between the coil length and the output voltage is linear, but the relationship of Vout to the coil width is proportional to that of the ratio ln (b / a), so that a larger increase of w or b (FIG. 1B ) is required to give any appreciable increase in coupling, thus maximizing the length of the coil is desired, if possible.

3 illustrates an example test configuration circuit 100 with a Vout output according to an embodiment of the invention. In the test configuration circuit 100 Double air coils with dimensions l = 38mm, w = 5mm, a = 10mm, consequently b = 15mm, were tested. The serial arc fault was generated on a vibrating table containing a loose terminal connection configuration under an arbitrary vibration according to the standards SAE AS5692. The test was carried out at a line voltage of 270 volts DC. The graphic representation in 4A illustrates this through a serial fault arc in the circuit 100 as they are in 3 is illustrated running current when a loose terminal is shaken while it is energized. The graphic representation in 4B illustrates the response of the amplified air coil output voltage, which shows a negative pulse during the negative dI / dt event caused by the occurrence of a serial fault arc. The amplitude of the pulse is amplified by a factor of 10 during the fault arc.

The embodiments described above provide numerous advantages, including the ability to detect serial and / or parallel fault arcs in AC and DC systems, and are particularly useful for detecting serial arc faults in high voltage systems. The embodiments described above may be used to detect both internal and external fault arcs for the printed circuit board. The air-flow transformer provides a means for determining the dI / dt signal in a power distribution feed power without having to measure the absolute current and without subsequently having to force differentiation of this signal. The above embodiments further provide an improved dynamic range of the dI / dt signal as compared to a differentiation of an absolute current signal. The embodiments described above further provide galvanic isolation of the current measuring system, allowing flexibility in any required signal processing circuit. In high-voltage systems, the current sense amplifier for the sensor used does not have to float on the line voltage, as a shunt current sensor on the high side would have to do. The embodiments described above can detect AC components of high-intensity DC currents without saturation, and provide good suppression of near-end interference sources as found in aircraft environments. The solution requires very few peripheral components and can be implemented cost-effectively compared to alternative solutions.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including the creation and use of any devices or systems, and performing any incorporated methods , The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

It is an apparatus and method for detecting a fault arc using a conductor 14 on a printed circuit board (PCB) 10 created, the energy from an external source of energy to electrical components on the circuit board 10 provides by detecting a value representing the rate of change of a current through the conductor 14 featuring flowing electricity. The device and method can be used to detect both internal faults within the circuit board 10 as well as external errors outside the circuit board 10 to detect.

LIST OF REFERENCE NUMBERS

10

Printed circuit board, printed circuit board (PCB)

11

microprocessor

12

circuit board

13

electric components

14

conductor

16

Arc fault detector

20

first air transformer

21

Arc fault detection circuit

22

second air transformer

24

winding

26

winding

28

arrow

30

Kitchen sink

32

openings

100

 configuration circuit

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• GB 12075347 [0001]

Claims (22)

Printed circuit board comprising: several electrical components; a power conductor configured to be coupled to a power supply external to the circuit board and to provide power to the plurality of electrical components; and an error arc detector having a first air transformer disposed proximate the conductor for coupling to a magnetic field generated by a current flowing through the conductor and providing an output voltage, Vout, indicative of the rate of change of the Current, dI / dt, which flows through the conductor is proportional. The printed circuit board of claim 1, wherein the error arc detector further comprises a signal processing circuit that receives Vout and detects a presence of an error arc. The printed circuit board of claim 2, further comprising at least one of a relay and a semiconductor power controller that decouples the power conductor from the power supply when a fault arc is detected. A printed circuit board according to any one of the preceding claims, wherein the error arc detector further comprises a second air transformer connected in series and out of phase with respect to the first air transformer and wherein the voltage across the first and second air transformers is Vout. The printed circuit board of claim 4, wherein the first and second air transformers are disposed proximate the conductor to constructively add positive and negative components of the magnetic field generated by the current flowing through the conductor. A printed circuit board according to claim 5, wherein the first and second air transformers are in anti-phase to effect constructive addition of the positive and negative components of the magnetic field. The printed circuit board of claim 6, wherein the first and second air transformers include first and second coils, respectively. A circuit board according to claim 7, wherein each of said first and second coils is formed by a winding wound in the same rotational direction. A circuit board according to claim 8, wherein each coil has at least one spiral. A circuit board according to claim 9, wherein each coil has a plurality of spirals arranged in different planes in the circuit board. A printed circuit board according to claim 8, wherein the winding comprises a track on the circuit board. The printed circuit board of claim 1, wherein the first air transformer has a first coil. A printed circuit board according to claim 12, wherein the first coil is formed by a winding wound in a same direction of rotation. A circuit board according to claim 13, wherein the coil comprises at least one spiral. The circuit board of claim 14, wherein the coil has a plurality of spirals disposed in different planes in the circuit board. The printed circuit board of claim 15, wherein the winding comprises a track on the circuit board. The printed circuit board according to claim 1, wherein the current conductor comprises a bus bar. A method of detecting a fault arc using a conductor on a circuit board that supplies power from an external power source to electrical components on the circuit board, the method comprising: sensing an amount indicative of the rate of change of a current flowing through the conductor through an air transformer which is arranged on the circuit board; and determining a fault arc condition based on the detected value. The method of claim 18, including sensing the value of at least two air transformers disposed proximate the conductor to constructively add positive and negative components of a magnetic field generated by the current flowing through a conductor. The method of claim 18, further comprising disconnecting the power conductor from the external power source. The method of claim 20, wherein the external power source has at least 60 volts. The method of claim 21, wherein the external power source has at least 220 volts.

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