System and method for identifying an arc in a system for inductively transmitting electrical power

Abstract

System and method for identifying an arc in a system for inductively transmitting electrical power, wherein the system has an elongated primary conductor into which an alternating current source impresses an alternating current, wherein a secondary winding is inductively coupled to the primary conductor, wherein the AC voltage signal is provided by the secondary winding, from which AC voltage signal a unipolar voltage signal is generated, wherein the unipolar voltage signal is derived as a function of time and monitored in terms of magnitude for exceeding of a threshold value.

Description

[0001] System and method for detecting an arc in a system for inductive transmission of electrical power

[0002] Description:

[0003] The invention relates to a system and a method for detecting an arc in a system for inductive transmission of electrical power,

[0004] It is well known that for rectification, a bridge rectifier feeds a capacitor so that a smoothed output voltage can be provided.

[0005] It is well known that an arc can occur when a cable breaks.

[0006] The invention is therefore based on the object of detecting the occurrence of an arc simply and reliably.

[0007] According to the invention, the object is achieved by the system according to the features specified in claim 1 and by the method according to the features specified in claim 14.

[0008] Important features of the invention in the system for inductive transmission of electrical power, in particular to a mobile part, are that the system has a device for arc detection, which has a circuit arrangement, in particular an AC-DC converter or rectifier, for generating a unipolar voltage signal from an alternating voltage signal, in particular with a known frequency fO, in particular with a variable amplitude of the alternating voltage signal, wherein the system has an elongated primary conductor, into which an alternating current source impresses an alternating current, wherein a secondary winding, in particular of a mobile part movable along the primary conductor, is inductively coupled to the primary conductor, wherein the alternating voltage signal is provided by the secondary winding, wherein the input-side alternating voltage signal is fed to a magnitude generator, wherein the circuit arrangement has a number N of low-pass filters,in particular PT1 filters, which are arranged in series, wherein the output signal of the absolute value generator is supplied to a first of the low-pass filters, wherein a first, in particular multi-element, proportional element is connected in series to the low-pass filters, in particular is designed to be integrated with one or more of the low-pass filters, wherein the output signal of the series circuit comprising the low-pass filters and the first proportional element is supplied to a summing element, to which the output signal of the absolute value generator is also supplied, wherein the output signal of the summing element is supplied to a further low-pass filter, the output signal of which is made available directly or via a second proportional element as the unipolar voltage signal or is supplied to a second filter stage, the output signal of which is made available as the unipolar voltage signal, wherein the unipolar voltage signal is supplied to a differentiating element,in particular for the temporal derivation of the unipolar voltage signal, the output signal of which is fed to a comparator, in particular which is suitable for monitoring the output signal of the differentiator for exceeding a threshold value, in particular and depending on the exceeding, issuing, displaying and / or forwarding a warning message and / or switching off the AC power source.

[0009] The advantage here is that arc detection can be carried out easily and reliably by achieving rectification with the lowest possible residual ripple and rapid build-up or decay of the unipolar voltage. This is because the values ​​required for the capacitances of the low-pass filters can be selected to be small. In particular, the time constant of each low-pass filter is very short compared to the period of the fundamental oscillation of the AC voltage signal. It is particularly advantageous to select the time constant such that the entire series circuit causes a phase shift of the fundamental oscillation of the AC voltage component of the magnitude of the AC voltage signal, in particular at 2*f0, 180°. In this way, this fundamental oscillation, which is twice the fundamental oscillation of the AC voltage signal, is suppressed by the superposition with the magnitude signal itself.The resulting signal is smoothed by the additional low-pass filter and can then optionally be smoothed by a second filter stage, which, for example, again comprises a series connection of low-pass elements, whose output signal is in turn fed to a summer with the input signal. The time constant of these low-pass elements is preferably matched to the fundamental oscillation of the remaining AC component present in the output signal of the additional low-pass filter, which is four times the frequency of the fundamental oscillation of the AC signal. Thus, the time constant of the low-pass elements is much smaller than that of the low-pass filters, in particular only half as large or even smaller.

[0010] The rectified signal then only needs to be temporally differentiated to enable threshold monitoring, which reliably detects the excessive current fluctuation caused by the arc. As soon as the threshold is exceeded, a warning message is displayed and / or forwarded. This enables measures such as shutting down the power source and thus stopping the alternating current impressed on the primary conductor.

[0011] In an advantageous embodiment, the proportionality factor K1 of the first proportional element is dimensioned such that twice the frequency of the AC voltage signal remaining in the signal after the first filter stage, i.e., 2*f0, is eliminated, and / or that, in particular at twice the frequency of the AC voltage signal, i.e., the fundamental frequency 2*f0 of the rectified signal, the amplitude of the fundamental oscillation of the AC component of the output signal of the series circuit comprising the low-pass filters and the first proportional element is equal to the amplitude of the fundamental oscillation of the AC component of the output signal of the magnitude generator. The advantage here is that the signal attenuation caused by the low-pass filters is compensated for at the fundamental frequency of the AC component, in particular, i.e., 2*f0, and is thus used equally during summation with the magnitude signal.

[0012] In an advantageous embodiment, the low-pass filters are dimensioned and / or the time constants of the low-pass filters are dimensioned such that at the frequency of the fundamental oscillation of the AC voltage component of the output signal of the magnitude generator, in particular at twice the fundamental oscillation frequency of the AC voltage signal, i.e., at the frequency 2*f0, the phase shift caused by the series connection is 180°. The advantage here is that the AC voltage component is reduced as much as possible.

[0013] In an advantageous embodiment, the respective time constant of each low-pass filter element is equal to half the inverse of the angular frequency of the AC signal, in particular the angular frequency of the fundamental oscillation of the AC signal, in particular so that at the frequency of the fundamental oscillation of the AC component of the output signal of the absolute value generator, in particular at twice the fundamental oscillation frequency of the AC signal, in particular at 2*f0, the phase shift caused by the series connection is 180°. The advantage here is that when the input signal is summed on the output side, both signals are 180° out of phase with each other with respect to their fundamental oscillation, in particular with the same amplitude, i.e., equally weighted consideration in each case.

[0014] In an advantageous embodiment, the number N is four, in particular, four low-pass filters are provided in series. The advantage here is that the smallest possible number of low-pass filters leads to the greatest possible suppression of the AC voltage component.

[0015] In an advantageous embodiment, the proportionality factor of the first proportional element is four. The advantage here is that each time constant at the frequency of the fundamental oscillation of the AC voltage component of the magnitude signal causes a respective phase shift of 45° per low-pass filter, thus causing an amplitude attenuation per low-pass filter by a factor of square root two, whereby the four amplitude attenuations of the series circuit can be compensated by multiplying by four. In an advantageous embodiment, the proportionality factor of the second proportional element is 1 / (1+N), in particular one fifth. The advantage here is that the mean value is calculated and the signal amplitude is adjusted to the input-side signal amplitude.

[0016] In an advantageous embodiment, the frequency, in particular the fundamental frequency or frequency of the fundamental oscillation, of the AC voltage signal has a value between 10 kHz and 1000 kHz. This is advantageous because the AC voltage component can be kept very small.

[0017] In an advantageous embodiment, the second filter stage has a number of M low-pass filters, in particular PT1 filters, which are arranged in series, wherein a third, in particular multi-piece, proportional element is connected in series to the low-pass filters, in particular is designed to be integrated with one or more of the low-pass filters, wherein the output signal of the series circuit comprising the low-pass filters and the third proportional element is fed to a summing element, to which the input signal of the first low-pass filter, in particular of the first low-pass filter of the series of low-pass filters, is also fed, wherein the output signal of the summing element is made available directly as the unipolar voltage signal or is passed via a fourth proportional element, the output signal of which is made available as the unipolar voltage signal.The advantage here is that the filter method can be used in two or more stages, whereby, however, the time constant of the second or subsequent filter stage is smaller, in particular at least half, than the time constant of the previous filter stage.

[0018] In an advantageous embodiment, the proportionality factor K3 of the third proportional element is dimensioned in such a way that the fourfold frequency of the

[0019] AC voltage signal, i.e. 4*f0, is eliminated, and / or that at four times the frequency of the AC voltage signal, i.e. at 4*f0, the amplitude of the output signal of the series circuit comprising the low-pass filters and the third proportional element, in particular the second filter stage, is equal to the amplitude of the input signal of this series circuit.

[0020] The advantage here is that the signal attenuation caused by the low-pass filters is compensated.

[0021] In an advantageous embodiment, the respective time constant of each low-pass filter is equal to half the time constant of the first of the low-pass filters, in particular, with all low-pass filters having the same time constant. It is advantageous that the time constant can be adapted to the higher frequency of the respective fundamental oscillation of the respective higher filter stage.

[0022] In an advantageous embodiment, the AC voltage signal is available at the DC-side terminal of a bridge rectifier, the AC-side terminal of which is fed from a secondary winding that is inductively coupled to a primary conductor, in particular coupled to a primary conductor laid elongately in a system, wherein an AC current is impressed into the primary conductor, in particular by a current source, in particular by a medium-frequency current source, in particular wherein the medium frequency has a value between 10 kHz and 1000 kHz. It is advantageous that a current source feeds the bridge rectifier in a galvanically decoupled manner. This makes it possible to measure a primary-side current in a galvanically decoupled manner.A specific application example is the output current of a power supply device whose output current is injected into an elongated line conductor, from which mobile devices whose secondary windings are inductively coupled to the line conductor are inductively supplied. Alternatively, the current measurement according to the invention can also be implemented on one of the aforementioned mobile devices by using a connecting cable of one of the aforementioned secondary windings as the primary conductor. In any case, a galvanically decoupled current measurement can be implemented, which is capable of detecting a high current without significantly influencing it.

[0023] In an advantageous embodiment, a first low-pass filter comprises a series circuit consisting of a first resistor (R2) and a capacitor (C1), whose connecting nodes feed the inverting input of a first operational amplifier via a second resistor (R3). The advantage here is that the low-pass filter is inexpensive and easy to implement.

[0024] In an advantageous embodiment, a second low-pass filter has a parallel circuit comprising a third resistor (R4) and a second capacitor (C2), which connects the inverting input of the first operational amplifier (OP1) to the output of the first operational amplifier, in particular wherein the first operational amplifier functions as part of the first proportional element, in particular wherein the signal amplification effected by the first operational amplifier functions as a portion of the proportionality factor K1, in particular the square root of K1, of the first proportional element. It is advantageous in this case that the low-pass filtering can be carried out jointly with an amplification.

[0025] In an advantageous embodiment, a third low-pass filter comprises a series circuit consisting of a fourth resistor (R5) and a capacitor (C3), whose connecting nodes feed the inverting input of a second operational amplifier via a fifth resistor (R6). The advantage here is that the low-pass filter is inexpensive and easy to implement.

[0026] In an advantageous embodiment, the third low-pass filter has a parallel circuit comprising a sixth resistor (R7) and a second capacitor (R4), which connects the inverting input of the second operational amplifier to the output of the second operational amplifier, in particular wherein the second operational amplifier functions as part of the first proportional element, in particular wherein the signal amplification effected by the second operational amplifier functions as a portion of the proportionality factor K1, in particular the square root of K1, of the first proportional element (14). It is advantageous that the low-pass filtering can be carried out jointly with an amplification. Important features of the method for detecting an arc in a system for inductive transmission of electrical power, in particular to a mobile device, are that the system has an elongated primary conductor,in which an alternating current source impresses an alternating current, wherein a secondary winding, in particular of a mobile part movable along the primary conductor, is inductively coupled to the primary conductor, wherein the alternating voltage signal is provided by the secondary winding, from which a unipolar voltage signal is generated, in particular by means of AC-DC conversion or rectification, in particular wherein the method is carried out with a system according to one of the preceding claims, characterized in that the magnitude, in particular a magnitude signal, of the alternating voltage signal supplied on the input side is formed, wherein the magnitude is supplied to a series circuit formed from N low-pass filters, in particular PT1 filters, wherein signal amplification is also carried out in the series circuit, in particular by means of one or more of the low-pass filters, wherein the output signal of the series circuit is supplied to a summing element,to which the amount is also fed, in particular directly, wherein the output signal of the summing element is fed to a further low-pass filter, the output signal of which is made available directly or amplified as the unipolar voltage signal or is fed to a second filter stage, the output signal of which is made available as the unipolar voltage signal, wherein the unipolar voltage signal is derived over time and monitored in terms of amount for exceeding a threshold value, in particular and depending on the exceeding, a warning message is issued, displayed and / or forwarded and / or the AC source is switched off.

[0027] The advantage here is that efficient rectification and smoothing can be achieved, especially with minimal hardware complexity. Another advantage is that low-pass filtering can be implemented together with amplification.

[0028] Further advantages emerge from the dependent claims. The invention is not limited to the combination of features in the claims. Further possible combinations of claims and / or individual claim features and / or features of the description and / or the figures will become apparent to those skilled in the art, particularly from the problem and / or the problem posed by comparison with the prior art.

[0029] The invention will now be explained in more detail using schematic illustrations:

[0030] Figure 1 schematically shows a first circuit arrangement for rectifying an alternating voltage signal, which is part of an arc detection device for a system according to the invention for inductive transmission of electrical power, in particular to a mobile part.

[0031] Figure 2 shows a schematic representation of a second circuit arrangement for rectifying the alternating voltage signal.

[0032] Figure 3 shows the corresponding voltage curves.

[0033] Figure 4 shows an exemplary embodiment of the first circuit arrangement

[0034] Figure 5 shows the AC voltage signal at which an arc event occurs.

[0035] Figure 6 shows the output signal 6 of the circuit arrangement as well as signals of the further signal processing in the device.

[0036] The system comprises a primary conductor laid elongately in a system, into which a medium-frequency alternating current is injected. A mobile unit arranged to be movable along the primary conductor has a secondary winding that is inductively coupled to the primary conductor. An energy storage device and / or traction drive of the mobile unit can be electrically supplied from the secondary winding.

[0037] Since the primary conductor is energized by a current source, an arcing event can occur if the primary conductor is accidentally separated, for example in the event of a cable break.

[0038] To detect this arcing event, the system includes the device that includes the rectifying circuitry and processes its output signal. As shown in Figure 1 together with Figure 3, in the circuitry, an alternating voltage signal 1 from an alternating voltage signal source 11 is fed to an AC-DC converter, in particular a rectifier, whose output signal is a unipolar voltage signal 6 with only a slight residual ripple. The frequency of this preferably sinusoidal alternating voltage signal is referred to below as f0.

[0039] In principle, it is noted that a signal rectified from a sinusoidal signal of frequency f0 has, in addition to a DC component, an AC component with the fundamental frequency 2*f0 and further AC components with the frequencies 4*f0, 6*f0, 8*f0, etc.

[0040] For this purpose, the alternating voltage signal 1 is first fed to a magnitude generator 12, the output signal of which is fed to, in particular, four low-pass filters 13 arranged in series. The first of these low-pass filters 13 causes a 45° phase shift of the output signal 2 of the magnitude generator 12. Since the second, third, and fourth low-pass filters 13 are identical in construction or at least all low-pass filters 13 have the same time constant, the output signal of the last of the series-arranged low-pass filters 13 has a 180° phase shift relative to the alternating voltage signal 1 supplied on the input side.

[0041] The output signals of the low-pass filters 13 arranged between the first and the last low-pass filter 13 are shown in Figure 3, wherein the residual ripple of the signal decreases with the number of low-pass filters 13 passed through.

[0042] The output signal of the last of the low-pass filters 13 arranged in series is fed to a proportional element 14, which compensates for the amplitude reduction of the alternating component having the frequency 2*f0 caused by the low-pass filters 13.

[0043] Preferably, the time constant of each of the low-pass filters 13 is designed such that, at the predetermined known fundamental frequency f0 of the AC voltage signal 1, the amplitude reduction of the AC component having the frequency 2*f0 at the output of the absolute value generator equals the inverse of the square root of two, in particular the amplitude at the output of each of the low-pass filters 13 equals the amplitude at its input divided by the square root of two. This results in the value four for the proportionality constant K1 of the proportional element 14. In particular, four low-pass filters 13 are used in the first filter stage. The thus adjusted output signal of the proportional element 14 is fed to a summing element, to which the output signal of the absolute value generator 12 is also fed. The sum formed by the summing element is fed to a further filter stage, which preferably consists of a proportional element 15 and a low-pass filter 16, in particular a PT1 element.The proportional element 15 multiplies its input signal by the proportionality constant K2.

[0044] By summing the two signals, which are shifted by 180° relative to each other, the output signal of the absolute value generator 12 is efficiently smoothed. The AC voltage component with the frequency 2*f0 is eliminated. The remaining higher-frequency AC voltage components at the output of the adder, in particular the frequencies 4*f0, 6*f0, 8*f0, ..., are efficiently smoothed by the low-pass filter 16.

[0045] As shown in Figure 2, further filtering of the output signal of the low-pass filter 16 is also possible by feeding the output signal to a further filter stage, in particular to a further series of low-pass filters 20, the time constant of which is selected such that the remaining AC voltage component, which has four times the frequency 4*f0, is suppressed as completely as possible. Here, too, the amplitude reduced at four times the frequency by the series of low-pass filters 20 is adjusted by a provided proportional element 21, for which the proportionality constant K3 of the proportional element 21 is selected accordingly. A downstream summer, in turn, forms the sum of the output signal of the proportional element 21 and the output signal of the low-pass filter 16. The output signal of the summer is then fed to a proportional element 22, which multiplies the proportionality constant K4.

[0046] Since the first filtering, in particular the part of Figure 2 contained in Figure 1, leaves a residual ripple with four times the frequency of the alternating voltage signal 1 , i.e. with 4*f0, the further filtering is geared to this and thus leaves only a residual ripple of an even higher frequency.

[0047] As shown in Figure 4, the low-pass filters 13 of the series of low-pass filters 13 can be designed differently.

[0048] In the specific embodiment according to Figure 4, instead of the alternating voltage source 11, a medium-frequency alternating current is impressed into a primary conductor from a current source. Via a current transformer, a secondary current proportional to the primary current is fed to the resistor R1 via the rectifier 12 acting as the absolute value generator, which is preferably implemented as a single-phase bridge rectifier with four diodes. The rectified secondary current generates a rectified voltage at the resistor R1 that is proportional to the primary current. The resistors R2 and R9 are very large compared to R1, so that the voltage at R1 is only slightly distorted. The voltage drop across the resistor R1 is fed to a first low-pass filter 13, consisting of a series connection of a resistor R2 with a capacitor C1 and a resistor R3 acting as a load resistor.Here, the connecting node of the series circuit, i.e. the connecting node of the resistor R2 with the capacitor O1, feeds the inverting input of a first operational amplifier OP1 via the resistor R3.

[0049] The non-inverting input of the operational amplifier OP1 is connected to ground and a DC side terminal of the bridge rectifier is also connected to ground.

[0050] The output of the first operational amplifier OP1 is connected to the inverting input of the first operational amplifier OP1 via a parallel circuit formed by a resistor R4 and a second capacitor O2.

[0051] The output of the first operational amplifier OP1 feeds a further RC element, which is formed as a series circuit of a resistor R5 and a third capacitor O3, wherein the inverting input of a second operational amplifier OP2 is fed from the connection node of this series circuit via the resistor R6, which is connected to the output of the second operational amplifier via a parallel circuit of a fourth capacitor O4 and a resistor R7.

[0052] The output voltage of the second operational amplifier OP2 is fed via a resistor R8 to a capacitor O5, to which the output voltage of the bridge rectifier present at the first resistor R1 is also fed, in particular summing, via a resistor R9. A smoothed output voltage is thus applied to this capacitor O5. The two parallel circuits, which connect the output of the respective operational amplifier to its inverting input, act as low-pass filters, just like the RC elements, with the operational amplifiers each providing a signal amplification that corresponds to the effect of the proportional element 14. In abstract terms, the proportional element 14 is designed in several pieces, in particular with each operational amplifier (OP1, OP2) providing an amplification by a factor of two.

[0053] Thus, the embodiment of Figure 4 implements the first filter stage according to Figure 1 or Figure 2 with four low-pass filters 13 and a first proportional element with the proportionality constant K1, integrated by means of the operational amplifiers (OP1 and OP2), as well as a summing element, which, by means of the connected capacitor O5, also acts as a smoothing additional low-pass filter 16. A second proportional element with the proportionality constant K2 can be added on the output side.

[0054] In further embodiments according to the invention, the proportional element 14 of the embodiment according to Figure 1 or 2 is provided at a different location of the low-pass filters 13 arranged in series or is designed in several parts and distributed in the series.

[0055] In further embodiments according to the invention, instead of the series-arranged, mutually identical low-pass filters 13, a low-pass filter arrangement is used which also generates the above-mentioned phase shift by 180° and has a gain, i.e. proportionality constant K1, such that the amplitude of the fundamental frequency 2*f0, i.e. of the signal provided by the absolute value generator 12, at the output of the low-pass filter arrangement is equal to the amplitude of the fundamental frequency 2*f0 at the output of the absolute value generator 12.

[0056] Thus, the gain, i.e. proportionality constant K1 , is: where F(j*w) represents the transfer function of the low-pass filter arrangement and

[0057] S = 4 * TT * j * f0w0= 2 * n * f Qwhere fo is the frequency of the AC signal and j is the square root of -1. In addition, the low-pass filter arrangement must be designed in such a way that it produces a phase shift of 180°, i.e. arg(F(s) = 180° arg( 180° applies. The proportionality constant K2 of the proportional element 15, to which the summed signal is fed, is always:

[0058] In this way, the DC component of the output signal of the second proportional element 15 is equal to the DC component of the output signal of the absolute value generator 12.

[0059] In an embodiment in which the low-pass filter arrangement is designed from a series of N low-pass filters 13 that are identical or different to one another, the following applies specifically to the amplification, i.e. proportionality constant K1: where F1 (j*w) to FN(j*w) represent the respective transfer function of the respective low-pass filter 13. However, according to the invention, the time constants of these low-pass filters 13 must be selected such that arg(Fl( / * 2 * w0) * F2(j * 2 * w0) * F3(j * 2 * w0) * ... * FN(j * 2 * w0)) = 180 applies, where for the respective low-pass filter numbered n = 1 to N, its time constant Tfj determines the transfer function as follows: where Fn(s) is the respective one of the transfer functions F1(j*w) to FN(j*w).

[0060] For a two-stage design analogous to Figure 2, the following applies: where the transfer functions F1 to FN are related to the low-pass filters 20.

[0061] In addition,

[0062] Thus, even in the two-stage version, the DC component on the output side is equal to the DC component of the output signal of the absolute value generator 12.

[0063] Since the realization with analog components deviates from tolerances, this equality always applies to the present invention within the scope of the deviations caused by the tolerances.

[0064] The above descriptions were initially based on a sinusoidal AC signal. However, the invention extends to other signal forms.

[0065] The voltage waveforms shown in Figure 3 occur when the AC voltage signal 1 is switched on.

[0066] The secondary voltage drop across the secondary winding inductively coupled to the primary conductor is used as AC voltage signal 1.

[0067] In the event of an arcing event, the alternating voltage signal 1 is briefly changed in the manner shown in Figure 5, since in the event of a break in the line, an increase in voltage of the alternating voltage signal 1 occurs, particularly after a zero voltage crossing, and an arc is ignited, which then acts as an electrical connection. In the event of an arcing event, the output signal 6 of the circuit arrangement, in particular of the rectifier, therefore exhibits a fluctuation which can be magnified by temporal differentiation, in particular first-order differentiation. According to the invention, the differentiated signal, in particular the differentiated signal freed of its moving average, in particular the pure alternating voltage component, is monitored for exceeding a threshold value, and the arcing event is thereby detected.

[0068] The threshold value is greater in magnitude than the background noise of the differentiated signal and smaller than the peak value of the differentiated signal occurring during an arcing event. As soon as the threshold is exceeded, the arcing event is detected, and appropriate measures can be initiated, such as forwarding and / or displaying a warning message and / or even shutting down the alternating current injected into the primary conductor.

[0069] In a further development of the described embodiment, the time-differentiated signal is low-pass filtered and only then monitored for exceeding a threshold value, thereby detecting the arc event.

[0070] Alternatively, instead of the time-differentiated signal, the output signal 6 can be low-pass filtered and fed to a subtractor, which determines the difference between the output signal 6 and the low-pass filtered output signal, which is then monitored for exceeding a threshold value and thus the arc event is detected.

[0071] In a further development, the reliability of arc detection can be improved by additionally evaluating the signal monitored for exceedance of the threshold value by a signal processing unit, which determines the maximum of the convolution function using a periodic function and then compares this with a second threshold value. If exceeded, the arc can be classified as reliably detected and displayed. The parameters of the periodic function are specified and, in the respective embodiment, depend on the respective inductance of the primary conductor and on a respective capacitance dependent on the primary conductor. List of reference symbols

[0072] 1 AC voltage signal

[0073] 2 Amount of the alternating voltage signal 1

[0074] 3 Signal voltage

[0075] 4 Signal voltage

[0076] 5 summing signal

[0077] 6 Output signal of the circuit arrangement, in particular the rectifier

[0078] 11 AC signal source

[0079] 12 amount generators

[0080] 13 Low-pass filters, especially PT1 filters

[0081] 14 Proportional element

[0082] 15 Proportional element

[0083] 16 low-pass filters, especially PT1 filters

[0084] 20 low-pass filters, especially PT1 filters

[0085] 21 Proportional element

[0086] 22 Proportional element

[0087] 61 Differentiated signal

[0088] 62 pure AC component of the differentiated signal

Claims

Patent claims:

1. A system for the inductive transmission of electrical power, in particular to a mobile part, wherein the system comprises a device for arc detection, which comprises a circuit arrangement, in particular an AC-DC converter or rectifier, for generating a unipolar voltage signal from an AC voltage signal, wherein the system comprises an elongated primary conductor into which an AC current source impresses an AC current, wherein a secondary winding, in particular of a mobile part movable along the primary conductor, is inductively coupled to the primary conductor, wherein the AC voltage signal is provided by the secondary winding, wherein the AC voltage signal on the input side of the circuit arrangement is fed to a magnitude generator, wherein the circuit arrangement comprises a number N of low-pass filters, in particular PT1 filters, which are arranged in series,wherein the output signal of the absolute value generator is fed to a first of the low-pass filters, wherein a first, in particular multi-element, proportional element is connected in series to the low-pass filters, in particular is designed to be integrated with one or more of the low-pass filters, wherein the output signal of the series circuit comprising the low-pass filters and the first proportional element is fed to a summing element, to which the output signal of the absolute value generator is also fed, wherein the output signal of the summing element is fed to a further low-pass filter, the output signal of which directly or via a second proportional element, as the unipolar voltage signal is provided or is fed to a second filter stage, the output signal of which is made available as the unipolar voltage signal, characterized in that the unipolar voltage signal is fed to a differentiator, in particular for the time-dependent derivation of the unipolar voltage signal, the output signal of which is fed directly or via a low-pass filter to a comparator, in particular which is suitable for monitoring the output signal of the differentiator for exceeding a threshold value, in particular and depending on the exceeding, for issuing, displaying and / or forwarding a warning message and / or switching off the AC source, or that the unipolar voltage signal is fed to a low-pass filter, the output signal of which is fed to a subtractor, to which the unipolar voltage signal is also fed, wherein the output signal of the subtractor,in particular, the difference between the output signal of the low-pass filter and the unipolar voltage signal is fed to a comparator, which is particularly suitable for monitoring the output signal of the subtractor for exceeding a threshold value, in particular and depending on the exceeding, issuing, displaying and / or forwarding a warning message and / or switching off the AC power source.

2. System according to claim 1, characterized in that the proportionality factor K1 of the first proportional element is dimensioned such that the double frequency of the alternating voltage signal remaining in the signal after the first filter stage, i.e. 2*f0, is eliminated, and / or that at the double frequency of the alternating voltage signal, i.e. fundamental frequency 2*f0 of the rectified signal, the amplitude of the fundamental oscillation of the alternating component of the output signal of the series circuit comprising the low-pass filters and the first proportional element is equal to the amplitude of the fundamental oscillation of the alternating component of the output signal of the absolute value generator.

3. System according to one of the preceding claims, characterized in that the low-pass filters are dimensioned in such a way and / or the time constants of the low-pass filters are dimensioned in such a way that at the frequency of the fundamental oscillation of the AC voltage component of the output signal of the absolute value generator, in particular at twice the fundamental oscillation frequency of the AC voltage signal, in particular at the frequency 2*f0, the phase shift caused by the series connection is 180°.

4. System according to one of the preceding claims, characterized in that the respective time constant of each low-pass element is equal to half the inverse of the angular frequency of the alternating voltage signal, in particular the angular frequency of the fundamental oscillation of the alternating voltage signal, in particular so that at the frequency of the fundamental oscillation of the alternating voltage component of the output signal of the absolute value generator, in particular at twice the fundamental oscillation frequency of the alternating voltage signal, the phase shift caused by the series connection is 180°.

5. System according to one of the preceding claims, characterized in that the number N is equal to four, in particular four low-pass filters are provided in the series circuit, and / or that the proportionality factor of the first proportional element is four, and / or that the proportionality factor of the second proportional element is 1 / ( 1 + N ), in particular one fifth, and / or that the frequency, in particular fundamental frequency or frequency of the fundamental oscillation, of the alternating voltage signal has a value between 10 kHz and 1000 kHz.

6. System according to one of the preceding claims, characterized in that the second filter stage has a number of M low-pass filters, in particular PT1 filters, which are arranged in series, wherein a third, in particular multi-piece, proportional element is connected in series to the low-pass filters, in particular is designed to be integrated with one or more of the low-pass filters, wherein the output signal of the series circuit comprising the low-pass filters and the third proportional element is fed to a summing element, to which the input signal of the first low-pass filter, in particular of the first low-pass filter of the series of low-pass filters, is also fed, wherein the output signal of the summing element is made available directly as the unipolar voltage signal or is passed via a fourth proportional element, the output signal of which is made available as the unipolar voltage signal.

7. System according to one of the preceding claims, characterized in that the proportionality factor K3 of the third proportional element is dimensioned such that the fourfold frequency of the alternating voltage signal remaining in the signal after the first filter stage, i.e. 4*f0, is eliminated, and / or that at fourfold the frequency of the alternating voltage signal, i.e. at 4*f0, the amplitude of the output signal of the series circuit comprising the low-pass filters and the third proportional element, in particular of the second filter stage, is equal to the amplitude of the input signal of this series circuit.

8. System according to one of the preceding claims, characterized in that the respective time constant of the respective low-pass filter is equal to half the time constant of the first of the low-pass filters, in particular wherein all low-pass filters have the same time constant.

9. System according to one of the preceding claims, characterized in that the alternating voltage signal is available at the DC voltage side connection of a bridge rectifier, the AC voltage side connection of which is fed from a secondary winding which is inductively coupled to a primary conductor, in particular coupled to a primary conductor laid elongately in a system, wherein an alternating current is impressed into the primary conductor in particular by a current source, in particular by a medium-frequency current source, in particular wherein the medium frequency has a value between 10 kHz and 1000 kHz.

10. System according to one of the preceding claims, characterized in that a first low-pass filter comprises a series circuit of a first resistor (R2) and a capacitor, from whose connecting node the inverting input of a first operational amplifier is fed via a second resistor (R3).

11. System according to one of the preceding claims, characterized in that a second low-pass filter has a parallel circuit comprising a third resistor (R4) and a second capacitor (C2), which connects the inverting input of the first operational amplifier to the output of the first operational amplifier, in particular wherein the first operational amplifier acts as part of the first proportional element, in particular wherein the signal amplification effected by the first operational amplifier (OP1) acts as a portion of the proportionality factor K1, in particular the square root of K1, of the first proportional element (14).

12. System according to one of the preceding claims, characterized in that a third low-pass filter has a series circuit comprising a fourth resistor (R5) and a capacitor (R3), from whose connecting node the inverting input of a second operational amplifier is fed via a fifth resistor (R6).

13. System according to one of the preceding claims, characterized in that the third low-pass filter has a parallel circuit comprising a sixth resistor (R7) and a second capacitor (R4), which connects the inverting input of the second operational amplifier to the output of the second operational amplifier, in particular wherein the second operational amplifier acts as part of the first proportional element, in particular wherein the signal amplification effected by the second operational amplifier acts as a proportion of the proportionality factor K1, in particular the square root of K1, of the first proportional element (14).

14. A method for detecting an arc in a system for inductively transmitting electrical power, in particular to a mobile part, wherein the system has an elongated primary conductor into which an alternating current source injects an alternating current, wherein a secondary winding, in particular of a mobile part movable along the primary conductor, is inductively coupled to the primary conductor, wherein the alternating voltage signal is provided by the secondary winding, from which a unipolar voltage signal is generated, in particular by means of AC-DC conversion or rectification, in particular wherein the method is carried out with a system according to one of the preceding claims, wherein the magnitude, in particular a magnitude signal, of the alternating voltage signal supplied on the input side is formed, wherein the magnitude is supplied to a series circuit formed from N low-pass filters, in particular PT1 filters,wherein a signal amplification is also carried out in the series circuit, in particular by means of one or more of the low-pass filters, wherein the output signal of the series circuit is fed to a summing element, to which the amount is also fed, in particular directly, wherein the output signal of the summing element is fed to a further low-pass filter, the output signal of which is made available directly or amplified as the unipolar voltage signal or is fed to a second filter stage, the output signal of which is made available as the unipolar voltage signal, characterized in that the unipolar voltage signal is derived over time, in particular is then low-pass filtered, and then its amount is monitored for exceeding a threshold value, in particular and depending on the exceeding, warning information is issued, displayed and / or forwarded and / or the AC power source is switched off, or that the unipolar voltage signal is low-pass filtered and the difference between this low-pass filtered unipolar voltage signal and the unipolar voltage signal itself is formed and then the signal thus created is monitored for its amount is monitored for exceeding a threshold value, in particular and depending on the exceeding, warning information is issued, displayed and / or forwarded and / or the AC power source is switched off.

15. Method according to one of the preceding claims, characterized in that the maximum of the convolution of the signal monitored for exceeding the threshold value is determined with a periodic function and compared with a further threshold value, upon exceeding which the arc detection is indicated as reliably detected, wherein the period duration of the periodic function is specified as a parameter depending on the inductance, in particular line inductance, of the primary conductor and a capacitance connected to the primary conductor.

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