Adapted power line and energy converter comprising at least one adapted power line

Abstract

The invention relates to an adapted power line and to an energy converter comprising at least one power line. The power line comprises at least one linear electrical conductor (40) and at least one resistive component (42), separate from the conductor and connected in parallel with the conductor over a portion of the linear electrical conductor (40), a value of the resistance of the resistive component being at least equal to ten times a resistance value of the linear electrical conductor (40) over the portion in question.

Description

DESCRIPTION Title of the invention: Adapted power electrical line and energy converter comprising at least one adapted power electrical line

[0001] The invention relates to an electrical power line for transporting electrical energy and an electrical energy converter comprising at least one electrical power line. The invention finds particular but not exclusive use in the aeronautical field.

[0002] An aircraft generally comprises a large number of electrical machines or electrical loads supplied with electrical power by an on-board electrical supply network. For example, flight controls, air conditioning systems and internal lighting use three-phase AC electrical machines. Other electrical machines may operate on direct current. The electrical power supplied to these machines is provided by means of power conversion devices connected to the on-board network, itself supplied by electrical generators and storage batteries located on board the aircraft, or by means of connection to a ground electrical supply network, enabling the aircraft to be supplied with electricity while parked on a runway.

[0003] Power conversion is most often carried out using static converters, particularly rectifiers and inverters. These converters tend to generate electromagnetic interference conducted by the power lines that connect them to the on-board network, to each other and to the loads consuming electrical power.

[0004] To limit the propagation of electromagnetic disturbances, it is common practice to have filtering means at the input and output of static converters. The filtering means are generally integrated into the converters or placed in the immediate vicinity of the converters. The filtering means are mainly made up of inductive elements formed of electrical conductors wound around magnetic cores. The wound electrical conductors must withstand the intensity of the current flowing through them, which requires large conductor cross-sections and masses. It is also common to supplement these inductive elements by capacitors. The presence of these filtering means is penalizing both in terms of on-board mass and size.

[0005] The invention aims to reduce certain electromagnetic disturbances by damping them so as to attenuate any possible resonances. The invention therefore makes it possible to limit the use of filtering means or at least to reduce their mass and volume.

[0006] To this end, the invention relates to an electrical power line comprising at least one linear electrical conductor and at least one resistive component, distinct from the conductor and connected in parallel with the conductor on a portion of the linear electrical conductor, a resistance value of the resistive component being at least equal to ten times a resistance value of the linear electrical conductor on the portion considered.

[0007] Advantageously, the resistance value of the resistive component is at most equal to 10000.(L / C) 1 / 2, L being the natural inductance of the linear electrical conductor on the portion considered, and C being the parasitic capacitance of the linear electrical conductor seen from the natural inductance of the linear electrical conductor.

[0008] According to one embodiment, the electrical conductor is a track printed on a substrate and the resistive component is a resistive wire connected to the track.

[0009] The resistive wire can be connected to the track only at both ends of the resistive wire. Alternatively, the resistive wire is connected to the track along the entire length of the resistive wire.

[0010] According to another embodiment, the electrical conductor is a track printed on a substrate, the electrical line comprising several resistive components arranged along the track.

[0011] Resistive components can be surface mounted on solder pads made in the track.

[0012] The invention also relates to a power converter comprising several switching components and at least one electrical line according to the invention, connecting an input or an output of the converter to at least one of the switching components.

[0013] The converter may be an inverter with several branches connected between two inputs of the inverter, in which an electrical line according to the invention connects each input to each branch.

[0014] The invention will be better understood and other advantages will appear on reading the detailed description of an embodiment given by way of example, a description illustrated by the attached drawing in which:

[0015] Figure 1 represents an electrical architecture in which the invention is implemented;

[0016] Figures 2a and 2b represent a first embodiment of an electrical line according to the invention;

[0017] Figure 3 represents another embodiment of an electrical line according to the invention;

[0018] For the sake of clarity, the same elements will have the same references in the different figures.

[0019] Figure 1 represents an electrical architecture 10 comprising two static converters: a rectifier 12 and an inverter 14. The electrical architecture 10 is well suited to equipping a vehicle, in particular an aircraft. The electrical architecture 10 comprises an AC network 16 making it possible to supply a load 18 such as for example a motor, through the rectifier 12 generating a DC voltage from the AC voltage from the AC network 16, and through the inverter 14 providing an AC voltage to the load 18 from the DC voltage.

[0020] The load 18 operates in three-phase alternating current. The inverter 14 is formed of three branches 14u, 14v and 14w, each of which generates one of the alternating phases from the direct voltage delivered by the rectifier 12. Each of the branches comprises two transistors T, for example of the IGBT type, each associated with a diode D called a freewheel diode. The inverter 14 can be defined as a stand-alone component. The transistors T and the diodes D can be called switching components. More precisely, within an encapsulation, the inverter 14 comprises the transistors T and the associated diodes D mounted on a common substrate to form the three branches 14u, 14v and 14w. Metallized tracks carried by the substrate provide the connections between the different switching components as well as to the inputs and outputs of the inverter 14. The inverter 14 also comprises a base plate arranged opposite the substrate and making it possible to evacuate the heat produced by the various components during their switching.

[0021] Furthermore, the components of the inverter 14 have a parasitic capacitance formed between the conduction channel of the component, the base plate and the radiator. This capacitance is due to the proximity between the conduction channel, the base plate and the radiator, proximity made necessary for the evacuation of the heat released during switching. In Figure 1, these parasitic capacitances are represented in dotted lines at reference 24.

[0022] In addition, the conductive tracks located inside the inverter 14 naturally have a parasitic inductance. Some parasitic inductances are shown in Figure 1 at reference 26.

[0023] Common mode disturbances can circulate in the electrical architecture 10. These disturbances, represented in dotted lines in FIG. 1, circulate mainly through an electrical ground 20 of the electrical architecture 10. The AC network 16 being connected to the ground 20, the disturbances are superimposed on the AC voltages of the AC network 16 and then on the DC voltages coming from the rectifier 12.

[0024] The disturbances can be amplified by a resonance of the parasitic capacitances 24 and the parasitic inductances 26.

[0025] Disturbances, in particular common mode disturbances, can be limited by means of inductive filters arranged for example on the DC network. As illustrated in Figure 1, a common mode filter 22 comprises two inductors arranged on the same magnetic core. In each of the inductors circulates a phase of the DC network. The inductors are made by means of electrical conductors wound on the common magnetic core. The electrical conductors forming the inductors are sized to support the useful current of the DC network. As a result, the conductor cross-sections are large. The magnetic core on which the conductors are wound is also bulky. This results in a significant weight and volume for the filter 22.

[0026] It is also possible to reduce disturbances by reducing the value of parasitic capacitances and inductances. This means of reduction is however limited due to the arrangement of the components in the inverter 14. More precisely, the dimensions of the components impose minimum track lengths preventing the reduction of parasitic inductances below a minimum threshold. Furthermore, the need to evacuate the heat generated during switching requires the presence of a base plate under the switching components generating parasitic capacitances which cannot be eliminated.

[0027] The invention makes it possible to dampen disturbances without reducing the values ​​of the parasitic components. By damping disturbances, the invention makes it possible to reduce the dimensions and weight of the filters, in particular filter 22, or even to eliminate the filters. The invention proposes to dampen disturbances by evacuating their energy into resistors. More precisely, the invention proposes to associate a resistor with the parasitic inductances of the tracks of a converter and more generally with the linear electrical conductors on which a significant current flows.

[0028] Except for superconductors, any electrical conductor has a resistance that depends on the resistivity of the material that constitutes it, the length and the cross-section of the conductor. Furthermore, any conductor has a natural inductance of the order of one micro Henry per meter. The invention proposes to place in parallel with the conductor or at least in parallel with a portion of the conductor, a resistor that allows the damping of high-frequency disturbances passing through the conductor and superimposed on the electrical power signal. To ensure the main function of the conductor, which is to allow the transmission of the useful signal (power signal), it is important not to increase its resistance. A resistive component placed in parallel with the conductor does not increase this resistance.

[0029] Internal tests have shown that by placing a resistive component with a value at least equal to ten times the resistance value of the conductor on the portion considered, the damping effect of high-frequency disturbances superimposed on the useful signal is notable.

[0030] As a first approach, considering only the natural inductance L of the conductor and neglecting its own resistance, the added resistive component of resistance R allows to create an RL type damping. In an inverter, or more generally in a converter, including electronic switches having parasitic capacitances 24 in particular when a switch is placed on a heat sink through a sole, the parasitic capacitance between the drain of the switch and the heat sink is of the order of 1.5 nano Farad. The damping generated by the resistive component is of the RLC type. The greater the resistance value, the greater the damping provided that part of the current conducted by the conductor also passes through the resistor.

[0031] In addition to taking into account the natural inductance of a line, the presence of metal parts near the conductor leads to the formation of a parasitic capacitance between the conductor and an inverter ground which is of the order of a few pico Farads per meter. Alternatively, it is possible to model a line using a series inductance and a parallel capacitance. This parasitic capacitance specific to the conductor is added to that of the switching components. When choosing the value of the resistor allowing damping, it is possible to take into account these different parasitic capacitances and of course the parasitic inductance of the conductor. In practice, to obtain good damping, the resistance value of the resistive component can be of the order of:

[0032] R = where R represents the resistance value of the resistive component, L the natural inductance of the conductor and C the parasitic capacitance, either of the conductor alone or of the conductor associated with the components of the inverter 14 seen from the inductance L. It is possible that the resistive component chosen has its own natural inductance, or even its own parasitic capacitance which can be taken into account in the modeling.

[0033] The resistance value of the resistive component should also not be too high. In some applications where compliance with electromagnetic interference standards must be respected, a slight attenuation of disturbances may be sufficient to ensure compliance with the standard. Internal tests have shown that a resistance value of the order of R = 10000 allows a attenuation of the order of 1dB of problematic disturbances. We will therefore retain this parametric value as the maximum resistance value of the resistive component so that the invention provides a technical effect.

[0034] The invention is well suited to implementation in a power converter and more particularly in an inverter. The invention is also of interest in an electrical line intended to carry a power signal in order to dampen the effects of high-frequency disturbances likely to be superimposed on the power signal, typically at low frequency or even a continuous signal.

[0035] The inverter 14 shown in Figure 1 comprises a substrate on which the transistors T and the diodes D are arranged. On this substrate are printed tracks for connecting the two inputs + and - of the inverter 14 to the three branches 14u, 14v and 14w. The inputs + and - are connected to the outputs of the rectifier 12 via the filter 22. Tracks, respectively 28u+, 28v+ and 28w+, connect the input + to each of the branches, respectively 14u, 14v and 14w. Similarly, tracks, respectively 28u-, 28v- and 28w-, connect the input - to each of the branches, respectively 14u, 14v and 14w. As seen previously, these tracks have parasitic inductances 26 shown in dotted lines in Figure 1. The invention proposes to associate a resistive component, respectively 30u+, 30v+, 30w+, 30u-, 30v-, 30w- in parallel with each of the tracks, respectively 28u+, 28v+ and 28w+, 28u-, 28v- and 28w-.These resistive components are used to dampen resonances that may occur in the parasitic inductances of the associated tracks. The position and connection of the resistive components are given as examples only. In practice, the position and connection depend on the actual geometry of the tracks on the substrate.

[0036] Figures 2a and 2b represent a first embodiment of a linear conductor 40 equipped with a resistive component 42. Figure 2a is represented in perspective and Figure 2b in section in a plane perpendicular to the main axis 44 in which the conductor 40 extends. In the example represented, the conductor 40 is a track printed on a substrate 46 and its main axis 44 is rectilinear. It is of course possible to implement the invention for a main axis having several straight portions connected with non-null angles and generally for a curved main axis.

[0037] The resistive component 42 is here a resistive wire pressed against the track 44. More precisely, the resistive wire 42 extends along an axis 48 parallel to the axis 44. The resistive wire 42 can be connected to the track 40 only at its ends 42a and 42b, as shown in FIG. 2a by means of solder pads 40a and 40b made in the track 40 and each connecting the ends 42a and 42b respectively. It is also possible to connect the resistive wire 42 by intermediate pads or even over the entire length of the resistive wire 42. The resistive wire 42 can be formed from a rigid component assembled on the track 40. Alternatively, it can be deposited in the form of a paste containing conductive particles such as carbon particles.

[0038] In Figures 2a and 2b, the resistive wire 42 is arranged in contact with the track 40. Alternatively, it is also possible to arrange the resistive wire offset from the track 40 and at a distance from it. It is also possible to arrange the resistive wire on the opposite face of the substrate 46 to that receiving the track 40.

[0039] The advantage of this first embodiment is to allow the implementation of a resistive component 42 produced according to the length of the track 40 or its portion considered, either by cutting a rigid resistive wire to the length of the track, or by depositing a paste following the axis 44 of the track.

[0040] The addition of a resistive wire 42 in parallel with the track portion 40 tends to increase the parasitic inductance of the connection between the two ends of the track, due to the natural inductance inherent in the resistive wire itself, which at first glance goes against the desired effect by increasing the parasitic inductance. Indeed, as seen above, the track has a natural inductance of the order of one micro Henry per meter. The added wire has approximately the same natural inductance. As a result, the assembly formed by the track and the resistive wire has an inductance of the order of twice that of the track taken in isolation. However, even if the parasitic inductance is doubled, damping any possible resonance of high-frequency disturbances by means of the resistance of the resistive wire 42 makes these disturbances less problematic for the entire electronic equipment, particularly in the case of an inverter.

[0041] Figure 3 shows another embodiment in which track 40 is also printed on substrate 46. In this embodiment several resistive components 50, 52 and 54 are connected to track 40. The resistive components can for example be surface mounted resistors and each connected to two solder pads made on track 40. Three resistive components 50, 52 and 54 are shown in Figure 3. It is of course possible to arrange as many as necessary along the track 40. Advantageously, the resistive components are arranged along the track with as few gaps as possible between each resistive component in order to limit the portions of the track 40 without resistive components in parallel. For this purpose, the track comprises intermediate pads 40c and 40d each connecting two consecutive resistive components, which makes it possible to arrange the resistive components in an almost contiguous manner.

[0042] For example, internal testing has shown that one Ohm surface-mounted resistors arranged closely along a track provide substantial damping of high-frequency disturbances propagating along the track 40.

[0043] There are different types of resistive components. Examples include carbon film resistors and wirewound resistors. Wirewound resistors have a higher natural inductance than carbon film resistors. Although carbon film resistors are a priori preferred, as they have a lower cost and add little inductance in parallel with the section of line in question, the use of a wirewound resistor can be of interest, particularly for shifting a resonant frequency of high-frequency disturbances by means of the inductance added by the resistive component itself.

[0044] It is possible to replace one of the resistive components 50, 52 and 54 with a capacitor and / or an inductor in order to best adapt the RLC type damping mentioned above. By resistive component, we mean any type of component having a resistive component, in particular a semiconductor. For example, it is possible to place a diode or two head-to-tail diodes in parallel with the portion of line considered. It is also possible to place a MOS FET type transistor connected on the one hand between the gate and the short-circuited drain and on the other hand the source. The resistive component is then the drain-source resistance. It is also possible to take advantage of the series resistance of a capacitor or an inductor then considered as a resistive component.

[0045] It is possible to distinguish several successive portions in the same linear electrical conductor. On a first portion, it is possible to connect a resistive component in parallel and leave the next portion without a resistive component. It is possible to model this conductor as two inductors in series only one of which is equipped with a resistive component. More generally, a linear electrical conductor can be divided into several portions, at least one of which is equipped with a resistive component connected in parallel with the portion in question. Other components connected in series and / or in parallel, on the same portion or on one or more other portions, can complete the damping obtained by the resistive component.

[0046] The embodiments of Figures 2a, 2b and 3 are particularly well suited to an inverter whose components are carried by a substrate formed by a printed circuit. The invention can be implemented in any other electronic equipment using a printed circuit.

Claims

CLAIMS 1. Power electrical line comprising at least one linear electrical conductor (28; 40) and at least one resistive component (30; 42; 50, 52, 54), separate from the conductor and connected in parallel with the conductor on a portion of the linear electrical conductor (28; 40), a resistance value of the resistive component being at least equal to ten times a resistance value of the linear electrical conductor (28; 40) on the portion considered.

2. Power line according to claim 1, in which the resistance value of the resistive component (30; 42; 50, 52, 54) is at most equal to 10000.(L / C) 1 / 2 , L being the natural inductance of the linear electrical conductor (28; 40) on the portion considered, and C being the parasitic capacitance of the linear electrical conductor (28; 40) seen from the natural inductance of the linear electrical conductor (28; 40).

3. Electrical line according to one of the preceding claims, in which the electrical conductor is a track (40) printed on a substrate (46) and in which the resistive component is a resistive wire (42) connected to the track (40).

4. Power line according to claim 3, wherein the resistive wire (42) is connected to the track (40) only at the two ends (42a, 42b) of the resistive wire (42).

5. The power line of claim 3, wherein the resistive wire (42) is connected to the track (40) along the entire length of the resistive wire (42).

6. Electrical line according to one of claims 1 or 2, in which the electrical conductor is a track (40) printed on a substrate (46), the electrical line comprising several resistive components (50, 52, 54) arranged along the track (40).

7. Power line according to claim 6, in which the resistive components are surface mounted on soldering pads made in the track (40).

8. Power converter comprising several switching components (T, D) and at least one electrical line according to one of the preceding claims, connecting an input or an output of the converter to at least one of the switching components (T, D).

9. Power converter according to claim 8, the converter being an inverter (14) with several branches (14u, 14v, 14w) connected between two inputs (+, -) of the inverter (14), in which an electrical line according to one of claims 1 to 7 connects each input to each branch.

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