Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N35/00—Magnetostrictive devices

Definitions

• the present invention relates to the field of devices for energy recovery. It relates in particular to a converter capable of converting a variation of magnetic energy into a potential difference.
• the magneto-electric converter comprises a stack of layers of magnetostrictive and piezoelectric materials.
• the invention also relates to an electricity generator comprising said converter.
• the combination of a magnetostrictive material and a piezoelectric material is particularly advantageous for the production of magneto-electric converters which can be integrated into electric generators.
• the present invention proposes a magnetoelectric converter comprising at least one layer of piezoelectric material and one layer of magnetostrictive material; them respectively polarization and magnetization axes of these layers extend perpendicularly to the main plane of the layers or reference plane.
• the magneto-electric converter is clamped, without degree of freedom along an axis normal to the reference plane, in a cage; the latter allows the application of stresses on the piezoelectric layer, due to the expansion or contraction of the magnetostrictive layer along the axis normal to the reference plane.
• the invention also proposes an electricity generator based on the aforementioned converter.
• the present invention relates to a magneto-electric converter, capable of converting a variation of a magnetic field into a potential difference between two electrical terminals, including:
• a stack having an upper face and a lower face, parallel to a reference plane, and comprising a first layer of piezoelectric material secured to a second layer of magnetostrictive material, the first layer and the second layer extending parallel to the plane and having respectively a polarization axis and a main axis of magnetization normal to the reference plane, the first layer being provided with two metal electrodes respectively connected to the two electrical terminals of the converter,
• a cage comprising two blocking walls respectively in contact, without degree of freedom, with the upper face and the lower face of the stack.
• the cage is formed of at least one non-magnetic material and whose Young's modulus is greater than that of the piezoelectric material of the first layer;
• the -at least one- non-magnetic material of the cage is chosen from among aluminum, steel, copper, silver, tungsten, glass and carbon fibers, high performance cements, organic glasses or minerals;
• each electrode of the first layer comprises a plurality of metal films: o extending parallel to the reference plane, o buried at different levels in the piezoelectric material, o and arranged alternately with the metal films of the other electrode;
• the cage is configured so that the two blocking walls apply a compressive prestress to the stack of between 1 MPa and 100 MPa;
• the stack comprises a third layer of piezoelectric material extending parallel to the reference plane, having a polarization axis normal to the reference plane and provided with two metal electrodes connected to the two electrical terminals, the first and the third layer taking the second sandwich layer;
• the magnetostrictive material is composed of Terfenol-D, Galfenol, Terbium Iron, Iron-Cobalt, Iron-Nickel or even Iron-Silicon-Boron;
• the piezoelectric material is composed of PZT, PMN-PT, PVDF, BaTi03 or even AlN.
• the invention also relates to an electricity generator comprising a magneto-electric converter as mentioned above, and a magnetic source able to generate a magnetic field normal to the reference plane, the magneto-electric converter and the magnetic source being able to move in translation or in rotation relative to each other, so as to induce variations in the magnetic field parallel to the main axis of magnetization or variations in a component of said magnetic field parallel to the main axis d magnetization.
• the magnetic source defines a space in which the magnetic field prevails, the magneto-electric converter being placed in said space;
• the electricity generator comprises a second magnetic source capable of generating a magnetic field oriented in the reference plane
• the magnetic source is formed by a Halbach cylinder, the magneto-electric converter being placed in the internal space of said cylinder;
• the magnetic source comprises two magnetic bars extending along a longitudinal axis parallel to the reference plane, arranged facing each other, and defining between them an internal space in which the magneto converter is placed -electric, each magnetic bar forming a Halbach network configured to generate a first sinusoidal magnetic field in the internal space, oriented along an axis normal to the reference plane.
• Figure 1 shows a magnetoelectric converter according to the invention
• Figure 2 shows an exploded view of a layer of piezoelectric material with electrodes comprising a plurality of buried metal films, in a magneto-electric converter according to the invention
• Figure 3 shows a curve of evolution of the deformation of the layer of piezoelectric material as a function of the Young's modulus of the material of the cage, in a magneto-electric converter according to the invention
• Figure 4 shows the electrical energy produced by an electricity generator comprising a magnetoelectric converter according to the invention, depending on the prestress applied to the stack of layers of said converter by the cage;
• Figure 5 shows a curve linking stress and strain for a layer of piezoelectric material of a magneto-electric converter according to the invention
• FIG.7 Figures 6 and 7 show a first embodiment of an electricity generator according to the invention
• FIG.8 shows a second embodiment of an electricity generator according to the invention.
• Figure 9 shows a third embodiment of an electricity generator according to the invention.
• Figures 10a and 10b show respectively an example of a magneto-electric converter according to the invention and a generator according to the invention
• Figure 11 shows another example of a magneto-electric converter according to the invention.
• Some figures are schematic representations which, for the purpose of readability, are not to scale.
• the thicknesses of the layers along the z axis are not necessarily to scale with respect to the lateral dimensions along the x and y axes.
• the invention relates to a magneto-electric converter 100, capable of converting a variation of a magnetic field B into a potential difference between two electrical terminals.
• the converter 100 includes a stack 10 having an upper face 10a and a lower face 10b, parallel to a reference plane (x,y).
• the stack 10 comprises at least one layer 1 of piezoelectric material (called first layer 1) extending parallel to the reference plane (x,y) and having a polarization axis P normal to the reference plane (x,y).
• first layer 1 of piezoelectric material
• the expression according to which a layer extends parallel to the reference plane (x,y) means that the lateral dimensions of said layer, in the plane (x,y), are significantly greater than its thickness according to the z-axis.
• the piezoelectric material of the first layer 1 may be chosen from PZT (lead titano-zirconia), PMN-PT (Pb (Mgi / 3Nb2 / 3) 03 -PbTi03), PVDF (polymer of vinylidene fluoride), BaTi03 (barium titanate) or AIN (aluminum nitride).
• PZT lead titano-zirconia
• PMN-PT Pb (Mgi / 3Nb2 / 3) 03 -PbTi03
• PVDF polymer of vinylidene fluoride
• BaTi03 barium titanate
• AIN aluminum nitride
• the first layer 1 is provided with two metal electrodes allowing the collection of electric charges during the operation of the converter 100. These electrodes are respectively connected to the two electric terminals of the said converter 100.
• each electrode 1a, 1b of the first layer 1 advantageously comprises a plurality of metallic films 1a', 1a'', 1a''', 1b', 1b'' extending parallel to the plane (x,y), buried at different levels in the piezoelectric material le, and arranged alternately with the metal films of the other electrode lb,la.
• two successive metallic films 1a′, 1b′ in the first layer 1 can be spaced apart by approximately 100 microns.
• Each metallic film 1a', 1a'', 1a''', 1b', 1b'' may have a thickness of the order of a few microns, for example 3 microns.
• each electrode 1a, 1b can be connected together by a conductive adhesive (for example epoxy) in the form of a ribbon preferably extending over a slice of the first layer 1.
• a conductive adhesive for example epoxy
• This configuration of electrodes 1a, 1b is known as the name of "multilayer piezoelectric stack” or “piezo stack” according to the Anglo-Saxon terminology.
• Such a configuration is perfectly suited for the first layer 1, which has a polarization axis P normal to the reference plane (x,y), because it allows effective charge collection over the entire thickness (along the z axis, parallel to the axis of polarization P) of the first layer 1.
• the stack 10 also comprises at least one layer 2 of magnetostrictive material (called second layer 2), extending parallel to the reference plane (x,y) and having an axis principal magnetization A normal to the reference plane (x,y) (figure 1).
• the second layer 2 is integral with the first layer 1 at an interface parallel to the reference plane (x,y).
• the two layers 1,2 are secured without degree of freedom, so that the deformation of the second layer 2 of magnetostrictive material is effectively transmitted to the first layer 1, the objective being to maximize the mechanical/electrical energy conversion.
• glues or strong adhesive substances can be implemented to ensure the joining of the two layers 1,2.
• the second layer 2 has a roughness, at its (or its) surfaces to be secured, of between 0.01 ⁇ m to 50 ⁇ m Ra (average roughness, measured by atomic force microscopy on scans of 20 microns x 20 microns per example).
• Such roughness is favorable to the adhesion of the glue and consequently to the mechanical joining of the layers 1,2; in particular, it improves the normal interfacial rigidity of the stack 10.
• the magnetostrictive material is chosen to have a magnetostrictive coefficient advantageously greater than 30 ppm. It may be crystalline or sintered Terfenol, Galfenol, Terbium Iron, Iron-Cobalt, Iron-Nickel or even amorphous Fe-Silicon-Boron (FeSiB).
• Terfenol-D alloy of iron and rare earths Tbo,3Üyo,7Fei,9 crystalline
• FZM vertical zone melting
• the longitudinal axis of the ingot which is the ⁇ 112> axis, is the preferential magnetization (or deformation) axis of the material.
• the second layer 2 comes from a transverse cut (that is to say normal to the longitudinal axis) of the ingot.
• the main axis of magnetization A here corresponds to the axis ⁇ 112> of the crystal of Terfenol-D, preferential axis of deformation under a magnetic field.
• the fact of taking advantage of the deformation under a magnetic field of the magnetostrictive material along its main axis of magnetization is particularly advantageous for maximizing the deformation transmitted to the first layer 1, and therefore for maximizing the associated charge collection in the piezoelectric material.
• the stack 10 of the magneto-electric converter 100 therefore comprises the first layer 1 and the second layer 2, as described above.
• the stack 10 comprises another layer 3 (known as the third layer 3) of piezoelectric material extending parallel to the reference plane (x,y).
• This third layer 3 has a polarization axis normal to the reference plane (x,y), collinear with the polarization axis P of the first layer 1.
• the third layer 3 is also provided with two metal electrodes connected to the two electrical terminals of the converter 100. In this particular mode, the first layer 1 and the third layer 3 sandwich the second layer 2, as shown in figure 1.
• the stack 10 comprises another layer of magnetostrictive material extending parallel to the reference plane (x,y), having a main axis of magnetization normal to the reference plane (x,y).
• the layers of magnetostrictive material (including the second layer 2) sandwich the first layer 1.
• its upper face 10a and its lower face 10b may each be formed by a layer of piezoelectric material or by a layer of magnetostrictive material.
• the stack 10 can have lateral dimensions, in the reference plane (x,y) of between 0.1 mm and 200 mm, and various shapes (square, circular, rectangular, polygonal, etc.) in this same plane.
• the layer(s) 1,3 of piezoelectric material may have a thickness, along the z axis, of between 1 micron and 100 mm, preferably between 1 micron and 25 mm, or even between 1 micron and 10 mm.
• the layer(s) 2 of magnetostrictive material may have a thickness, along the z axis, of between 1 micron and 100 mm, preferably between 1 micron and 50 mm, or even between 1 micron and 25 mm.
• the total thickness of the stack 10 will be between 10 microns and 200 mm.
• the total thickness of the stack 10 will be chosen to be less than 80mm, or even less than 30mm.
• the magneto-electric converter 100 further comprises a cage 20 comprising two blocking walls 21, 22 respectively in contact, without degree of freedom, with the upper face 10a and the lower face 10b of the stack 10. in other words, the internal surfaces of the blocking walls 21, 22 bear flat respectively against the upper face 10a and the lower face 10b of the stack 10, and prevent any movement or displacement of the stack 10 along 1' z-axis.
• a deformation D along its main axis of magnetization A (parallel to the axis z) of the second layer 2 will directly induce a deformation d of the first layer 1 of piezoelectric material along its axis of polarization P, said first layer 1 having no possibility of moving along the z axis, due to the firm hold of the blocking walls 21,22.
• the deformation D corresponds to an extension of the second layer 2
• the deformation d will correspond to a contraction of the first layer 1
• the deformation D corresponds to a contraction of the second layer 2
• the deformation d will correspond to an extension of the first layer 1.
• the cage 20 is formed from at least one non-magnetic material, to avoid disturbing the magnetic field which will be applied to the converter 100, during its operation in an electricity generator.
• non-magnetic material is meant a material or a composite without magnetic properties but also a material whose magnetic susceptibility is low or very low, therefore a paramagnetic or diamagnetic material.
• the Young's modulus of the -at least one- material constituting the cage 20 is greater than that of the piezoelectric material of the first layer 1: this allows more effective transmission of the deformation of the second layer 2 to the first layer 1 because said deformation is not "attenuated” in whole or in part by a deformation of the walls 21,22 of the cage 20.
• the walls 21,22 of the cage 20 have a thickness of 8mm. Note that a maximum deformation is reached when the material of the cage 20 has a Young's modulus greater than or equal to approximately 200 GPa.
• the magneto-electric converter 100 it is always possible to increase the dimensions (thickness in particular) of the first layer 1 and/or of the second layer 2, or the thickness of the walls 21,22 of the cage 20, or else the intensity of the magnetic field B, to generate a greater deformation of the first layer 1 and consequently a greater quantity of electric charges.
• one objective of the magneto-electric converter 100 according to the invention is to be integrated into an electricity generator of small size, compact, and easy to associate with connected objects to make them self-sufficient in energy.
• the lateral dimensions of converter 100 are therefore preferably kept less than 15 mm, and its thickness less than 50 mm, or even less than or equal to 15 mm. Dimensions of a converter 100 according to the invention are shown in Figure 7, by way of example.
• the cage 20 is configured so that the two blocking walls 21,22 apply a prestress in compression, along the z axis (in other words, along the axes of polarization P and magnetization A), to stack 10, thus favoring flat support conditions.
• the prestress is between 1 MPa and 100 MPa, preferentially between 10 MPa and 30 MPa, or even preferentially between 1 MPa and 20 MPa
• the prestress may in particular be applied by a mechanical system with screws and nuts (the progressive screwing making it possible to increase the prestress applied by the cage 20), by a system of cables and pulleys or else by a counter-deflection system (a deformation of the cage 20 is operated before insertion of the stack 10; after assembly, the cage 20 applies a prestress to said stack 10).
• the electrical energy supplied by the converter 100 increases with the increase in the compression prestress applied to the stack 10.
• the stack 10 and the magnetic field B applied are the same as those stated with reference to Figure 3, and the cage 20 is made of austenitic steel.
• the electrical energy, proportional to the quantity of electrical charges collected due to the deformation of the first layer 1, can go from approximately 10 microJoule to approximately 150 microJoule, for a prestress ranging from 0 to 50 MPa in the example given .
• the increase in electrical energy comes in particular from the fact that the magnetostriction coefficient of the magnetostrictive material (second layer 2) increases when a prestress is applied to it.
• the deformation D along the main axis of magnetization A is therefore greater, which increases the deformation d, and therefore the generation of charges, in the first layer 1.
• the magnetostriction coefficient tends to decrease beyond a critical prestress (typically around 20 MPa). Care will then be taken to apply a prestress lower than this critical value.
• a layer 1.3 of piezoelectric material supports stress better in compression than in elongation.
• the rupture limit in elongation is reached more quickly than the rupture limit in compression of the piezoelectric material.
• Pre-stressing the stack 10, and therefore pre-stressing the layer(s) 1,3 of piezoelectric material makes it possible to position the operating range in a compressive stress zone (operating range with pre-stress), as illustrated in Figure 5.
• the application of a prestress to the stack 10 thus makes it possible to increase its reliability and its service life, by moving the operating range of the layer 1,3 of material piezoelectric of its voltage breaking limit.
• the blocking walls 21,22 can in particular be machined so as to create indentations in which the upper face 10a and the lower face 10b of the stack 10 will be placed and glued respectively. It is important to ensure good flatness of the surfaces intended to be in contact with the faces of the stack 10, to guarantee flat support, and effective blocking or prestressing along the z axis (parallel to the main axis of magnetization A).
• the cage 20 advantageously comprises at least one side wall 23 to interconnect the two locking walls 21,22.
• a fixed or removable cage can be considered, based on known fixing techniques such as welding, screwing, clipping, etc.
• the cage 20 can optionally be assisted by a prestressing system based on cables, counter-deflection or expansion of the hot frame.
• the cage 20 can be used to provide access to the electrical terminals of the converter 100 from the outside.
• the cage 20 is composed of two parts, a frame 20a and a typically cylindrical cover 20b, intended to cooperate to form the two locking walls 21,22 of the cage 20 ( Figure 10a ( a),(b)).
• These two parts 20a, 20b respectively comprise an internal thread and a thread.
• the diameter, the width of the pitch and the angle of the pitch are sized to exert a specific prestress on the stack 10.
• known anti-loosening techniques can be implemented, to limit the loosening between the frame 20a and the cover 20b over time: for example by using a nylon insert or an anti-loosening washer. This loosening phenomenon occurs in particular in a context of vibratory environment.
• a hexagonal bore 200b can be provided (FIG. 10a (c)) in order to insert a tightening tool facilitating the fixing of the cover 20b on the frame 20a.
• the entire system is sized so that the second layer 2 of magnetostrictive material transmits the maximum deformations onto the first 1 and (when present) the third 3 layer of piezoelectric material ( Figure 10a (c)).
• the cage 20 has a deformable parallelogram structure (FIG. 11 (a), (b)).
• the material, the shape and the thickness (or the thicknesses of the various segments making up the cage 20) of the cage 20 will dimension its stiffness, and consequently, the specific prestress which will be applied to the stack 10 when the latter is introduced. in the cage 20 (FIG. 11 (c)).
• the shape of the cage 20 and the material used can be optimized to exert a specific prestress on the stack 10, while retaining an initial deformation capacity which allows the stack 10 to be inserted into the interior space of the cage 20.
• the inner left and right sides of the cage have a flat support and must be designed to be as parallel as possible, in order to apply a uniform force on the stack 10.
• each cage design considered must be designed to have the maximum rigidity in order to effectively transmit the stresses and deformations of the magnetostrictive material to the piezoelectric material.
• the chosen design must allow precise adjustment of the preload, modulated by the geometric dimensions of the cage 20 and by the mechanical properties of the material used, so as not to damage the stack 10 and take advantage of the piezoelectric material once compressed.
• the present invention also relates to an electricity generator 150 comprising a magneto-electric converter 100 as described above.
• the generator 150 further comprises a magnetic source 50 capable of generating a magnetic field B normal to the reference plane (x,y), in other words parallel to the main axis of magnetization A of the second layer 2 and to the axis polarization P of the first layer 1.
• the magneto-electric converter 100 and the magnetic source 50 are capable of moving in translation or in rotation with respect to each other, so as to induce variations in magnetic field B.
• it is sought to induce variations in the amplitude of the magnetic field B along the z axis parallel to the main axis of magnetization A, or variations in a component of the magnetic field B parallel to the main axis of magnetization A.
• Amplitude variations between 0 and 300 mT are typically expected.
• the principle of operation of the generator 150 is schematized in FIG. 6, in the case of a relative movement, between the converter 100 and the magnetic source, in translation along the axis z.
• an initial state 0 the converter 100 is placed in a space in which there is a magnetic field of intensity Bo.
• This initial state corresponds to a deformation Do (for example, maximum elongation) of the second layer 2 along the main magnetization axis A and to an initial deformation do (for example, maximum contraction) of the first layer 1 along its axis P polarization; it is assumed that the potential between the terminals of converter 100 is zero in this initial state.
• the converter 100 is moved vis-à-vis the magnetic source 50 (or vice versa), and undergoes a magnetic field variation: the intensity of the latter passes from Bo to Bi, according to the z-axis.
• a deformation Di (for example, contraction) of the second layer 2, along the axis of magnetization A, is generated, which leads to a deformation di (for example, elongation) of the first layer 1 along its axis of polarization P.
• a quantity Qi of charges is then produced, inducing a potential difference between the metal electrodes 1a, 1b and consequently between the terminals of the converter 100. The charges are then collected, and the potential between the terminals of the converter 100 is found at 0.
• a following state 2 (which may be the initial state 0, if the relative displacement of the source 50 and the converter 100 passes through only two positions), the converter 100 is moved vis-à-vis the magnetic source 50 (or vice versa), and undergoes a magnetic field variation: the intensity of the latter changes from Bi to B2, along the z axis.
• a deformation D2 of the second layer 2, along the magnetization axis A, is generated, which leads to a deformation d2 of the first layer 1.
• a quantity Q2 of charges is then produced inducing a potential difference between the terminals of converter 100. The charges are then collected, and the potential at the terminals of converter 100 is found at 0.
• a following state 3 (which may be the initial state 0, if the relative displacement of the source 50 and of the converter 100 only passes through three positions), the converter 100 is once again moved with respect to the magnetic source 50 (or vice versa), and undergoes a magnetic field variation: the intensity of the latter changes from Eh to Eh, along the z axis.
• a deformation D3 of the second layer 2, along the magnetization axis A, is generated, which leads to a deformation d 3 of the first layer 1.
• a quantity Q 3 of charges is then produced inducing a potential difference between the electrical terminals of the converter 100. After collection of the charges, the potential between the terminals of the converter 100 is found again at 0.
• the following state 4 corresponds to the initial state 0, but it could be envisaged that there exist other distinct states associated with successive displacements of the converter 100 with respect to the magnetic source 50.
• the converter 100 sees the intensity of the magnetic field vary from B 3 to Bo, along the z axis.
• the deformation Do of the second layer 2, along the axis of magnetization A, is generated, which leads to the initial deformation do of the first layer 1 along its axis of polarization P.
• a quantity Qo of charges is then produced inducing a potential difference between the terminals of converter 100.
• the charges are then collected, to cancel the potential at the terminals of converter 100.
• the operation of the electricity generator 150 is based on an oscillatory dynamic behavior at the level of the stack 10 of the magneto-electric converter 100.
• the generator 150 is provided with a collection circuit (not shown in the figures), connected to the two electrical terminals of the converter 100, to collect the charges Q x produced. This collection circuit is arranged outside the cage 20.
• the intensity of the magnetic field, along the z axis is also preferable for the intensity of the magnetic field, along the z axis, to vary continuously between each state and not abruptly when passing between two positions corresponding to two successive states. This makes it possible to obtain a regular and periodic state of stress-strain that can be easily exploited by the electronics (periodic electrical intensity and voltage).
• the intensity of the magnetic field B varies sinusoidally along the main axis of magnetization A with values between 0 mT to 300 mT.
• Figure 8 illustrates such a configuration.
• the magneto-electric converter 100 is configured to move relative to the magnetic source 50, between a position corresponding to state 0 and a position corresponding to a state 4 equivalent to state 0. Between these two positions, the converter 100 will go through intermediate states (states 1, 2 and 3). During displacements, in translation, to go (state 0 to state 4) and return (state 4 to state 0), the converter 100 sees the intensity of the magnetic field B vary continuously along a sinusoid.
• the second layer 2 of magnetostrictive material will pass from a maximum contraction (state 0) to a slightly deformed state (state 1), then to a maximum elongation (state 2) to return to a slightly deformed condition (state 3).
• the layer(s) 1,3 of piezoelectric material undergoes significant deformation generating electric charges which are collected before switching to the next state.
• the charges could alternatively be collected only at the end of a cycle extending over two states: for example, the recovery of the charges can be operated at state 0, at state 2 and at state 4.
• the magnetic source 50 comprises two magnetic bars 51,52 forming Halbach networks.
• a Halbach network is in the form of a bar 51,52 with a succession of adjacent magnets whose particular arrangement increases the magnetic field on one side (internal space side of the magnetic source 50), while eliminating almost completely the magnetic field on the other side (external side of the magnetic source 50). This is achieved by rotating the orientations of the magnetic fields on successive magnets.
• the magnetic source 50 of the electricity generator 150 can therefore consist of two magnetic bars forming Halbach networks, the longitudinal axis y of each bar being arranged in the reference plane (x,y) .
• the relative movement between the converter 100 and the magnetic source 50 is then a movement in translation, along said longitudinal axis (axis y in the example of FIG. 8).
• the magnetic source 50 may consist of a Halbach cylinder, in the internal space of which there is a magnetic field B along the z axis, collinear with the main axis d magnetization A of the second layer 2 and with the axis of polarization P of the first layer 1.
• the relative movement between the magnetic source 50 and the converter 100 is preferably a translation along the z axis.
• the electricity generator 150 comprises a second magnetic source 60, capable of generating a magnetic field b oriented in the reference plane (x,y).
• the first 50 and the second 60 magnetic sources may consist of superposed Halbach cylinders, each inducing perpendicular magnetic fields B, b, namely one parallel to the z axis, the other parallel to a reference plane axis (x,y).
• the initial state 0 magnetic field B corresponds to a maximum elongation of the second layer 2 along the main axis of magnetization A (and therefore to a maximum contraction of the first layer 1 along its axis of polarization P) ; in the following state 1, the magnetic field B along the z axis is zero, which will cause a contraction of the second layer 2 along its magnetization axis A, accentuated by the presence of the magnetic field b along the y axis which promotes the deformation of the second layer 2 of magnetostrictive material in the plane (x,y) ⁇
• the relative movement between the magnetic source 50 and the converter 100 is a round trip translation.
• Figure 10b also illustrates a generator 150 in which the magneto-electric converter 100 is configured to move relative to the magnetic source 50 by translation round trip.
• the magnetic source 50 is not placed outside the cage 20 but inside the latter.
• the relative movement between the magnetic source 50 (for example, consisting of magnets) and the converter 100 is made possible by the presence of elastic elements (such as springs) which make it possible to move the source between different positions.
• elastic elements such as springs

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