Device and method for filtering electromagnetic interference

Abstract

A device that filters electromagnetic interference includes electrical conductors mounted in parallel. Each conductor includes a first coil positioned between a first and a second end of the respective conductor. Each first coil is coupled magnetically to each other first coil and has the same number of turns as each other first coil. The first and second ends of each of the conductors, respectively, are first and second terminals for the device. The device includes capacitors. Each capacitor is mounted between the second end of a corresponding electrical conductor and a third terminal of the device. The device includes an additional circuit. The additional circuit includes a second coil coupled magnetically with the first coils of the conductors. The additional circuit includes an additional coil. The second coil has a second number of turns.

Claims

1. A device for filtering electromagnetic interference, comprising: a plurality of electrical conductors mounted in parallel, each conductor comprising a first coil positioned between a first and a second end of the respective conductor, said first coils being coupled magnetically together and having a same first number of turns, said first and second ends of each of the conductors respectively defining first and second terminals for the device; a plurality of capacitors, each capacitor being mounted between the second end of a corresponding electrical conductor and a third terminal of the device; and an additional circuit comprising: a second coil coupled magnetically with the first coils, and an additional coil magnetically separated from the first coils, wherein the second coil has a second number of turns.

2. The device as claimed in claim 1, the ratio between the first number of turns and the second number of turns is greater than three.

3. The device as claimed in claim 1, wherein the additional circuit comprises a resistor.

4. The device as claimed in claim 3, the second coil, the additional coil and the resistor being mounted in series.

5. The device as claimed in claim 1, wherein the number of electrical conductors is equal to three.

6. The device as claimed in claim 1, the first coils and the second coil are wound around a same magnetic core.

7. The device as claimed in claim 6, the core being configured so as to exhibit a mutual inductance value of between 1 mH and 10 mH at a frequency of 10 kHz.

8. A method for filtering electromagnetic interference when electrical energy is transformed from an electrical network to an electrical energy storage unit and vice versa, the method comprising: performing filtering by interposing, between the electrical network and the energy storage unit, a device as claimed in claim 1.

9. The method as claimed in claim 8, in which the first terminals of the device are linked to the electrical network, the second terminals of the device are linked to the energy storage unit, and the third terminal of the device is linked to the earth.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention will be able to be better understood on reading the following description of a nonlimiting exemplary implementation thereof and on studying the attached drawing in which:

(2) FIGS. 1 to 3 schematically represent examples of electromagnetic interference filtering devices already known from the prior art and already described,

(3) FIG. 4 schematically represents an exemplary electromagnetic interference filtering device according to the invention, and

(4) FIG. 5 is a Bode diagram showing the gain response of the filtering devices represented in FIGS. 1 to 4.

DETAILED DESCRIPTION

(5) FIG. 4 represents an electromagnetic interference filtering device 1 according to an exemplary implementation of the invention. This device 1 is, in this example, incorporated in a three-phase power supply line interposed between a three-phase electrical network that is not represented and an electrical energy storage unit that is not represented. This electrical energy storage unit is, for example, a battery powering an electric vehicle motor used to propel the vehicle.

(6) The line comprises, at the level of the device 1, three electrical conductors 5 which each extend between a first end 7 and a second end 8, said ends 7 and 8 forming first terminals 7 and second terminals 8 for the device 1.

(7) Between the ends 7 and 8, each electrical conductor 5 comprises a first coil 10. The first coils 10 each comprise a same first number of turns and they are wound around a common magnetic core, being coupled magnetically together. These first coils 10 thus form a common mode inductance.

(8) The device 1 further comprises a capacitor 13 positioned between each second end 8 of a conductor and a third common terminal 15 of the device 1. As represented its FIG. 4, this third terminal 15 is, here, linked to the earth.

(9) For each phase of the electrical signal conveyed by the line, a first coil 10 and a capacitor 13 form an LC filter similar to the filter 100 described with reference to FIG. 1.

(10) As can be seen in FIG. 4, the device 1 further comprises an additional circuit 20 which, in this example, comprises a second coil 21 wound around the magnetic core around which the first coils 10 are also wound.

(11) The second coil 21 has a second number of turns which is, here, less than the first number of turns. The first number of turns and the second number of turns can be chosen relative to one another such that the ratio between this first and this second number of turns is greater than three.

(12) As represented in FIG. 4, the additional circuit 20 can comprise an additional coil 23 in series with a resistor 24 and the second coil 21.

(13) The additional coil 23 and the resistor 24 thus make it possible to produce a damping of LR type of the resonance at the cutoff frequency of the LC filter formed by each first coil 10-capacitor 13 pair.

(14) As can be seen, the additional circuit 20 need not have any electrical connection with the rest of the device 1, being linked thereto only by the magnetic coupling provided by the common magnetic core.

(15) In one example, the common magnetic core is configured in such a way that the mutual impedance value between the different coils 10 or 23 wound around this core is 8.5 mH at 10 kHz. Still in this example, each capacitor 13 has a capacitance of 22 nF, the first number of HEMS is equal to fourteen, and the second number of turns is equal to four. The additional coil 23 can then exhibit an impedance at 10 kHz of 15.6 mH and the resistor 24 can have a value of 18.

(16) FIG. 5 is a Bode diagram representing the gain of the filtering devices described with reference to FIGS. 1 to 4.

(17) The curve 200 corresponds to the device 100 of FIG. 1, the curve 210 corresponds to the device 110 of FIG. 2, the curve 220 corresponds to the device 120 of FIG. 3 and the curve 230 corresponds to the device 1 of FIG. 4.

(18) As can be seen, the device 1 makes it possible to significantly damp the resonance occurring at the cutoff frequency of the device 100.

(19) It can be observed that the frequency response in terms of gain of the device 1 according to the invention remains very close to that of the device 120 of FIG. 3 up to the mean frequency values.

(20) On the one hand, it can be observed that the resonance at the cutoff frequency of the LC filter formed by each first coil 10 and a capacitor 13 is damped. Beyond this cutoff frequency, it is observed that the device according to the invention makes it possible to obtain the response closest to that of the LC filter formed by each first coil 10 and a capacitor 13.

(21) The cutoff frequency of said LC filter is, for example, between 10 kHz and 100 kHz, being for example of the order of 8 kHz.

(22) The invention is not limited to the example which has just been described.

(23) In particular, in another example, the additional circuit 20 need not have a resistor 24, the damping of LR type provided by the additional circuit 20 then being obtained by virtue of the additional coil 23 and by the second coil 21 which then act both as inductor and as resistor via their internal resistance.

(24) The expression comprising a should be understood to be synonymous with the expression comprising at least one, unless otherwise specified.