Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
  • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
  • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
  • G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
  • G01R15/185—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core with compensation or feedback windings or interacting coils, e.g. 0-flux sensors
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
  • G01R19/18—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using conversion of DC into AC, e.g. with choppers
  • G01R19/20—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using conversion of DC into AC, e.g. with choppers using transductors, i.e. a magnetic core transducer the saturation of which is cyclically reversed by an AC source on the secondary side
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
  • G01R31/005—Testing of electric installations on transport means
  • G01R31/008—Testing of electric installations on transport means on air- or spacecraft, railway rolling stock or sea-going vessels

Definitions

• the subject of the invention is an improved current sensor isolated and adapted to the servo-controlled devices of the onboard avionic power electronics.
• the field of the invention is that of current sensors. More particularly, the field of the invention is that of the servocontrol / control of power electronics devices that develop significantly in aeronautics, automotive, rail and energy. In these electronic systems, the measurement of the "current" physical quantity is indeed a control variable that must be measured in order to control the device.
• An object of the invention is to provide a sensor adapted to the avionics environment and in particular a sensor that supports a large variation in temperature.
• Another object of the invention is to provide a sensor having a wide range of use.
• Yet another object of the invention is to provide a sensor having good linearity.
• the currents to be measured circulate in high-voltage conductors (hundreds of volts), and it is not easy to extract this measurement and bring it back to the level of the electrical mass.
• a resistor is an element with high heat dissipation.
• For a current measurement is generally chosen to be of low value to minimize dissipation losses, but then the disadvantage of having to measure very low voltage values (of the order of a few millivolts) for the low currents, which causes a significant loss of precision. It then becomes necessary to make a compromise between precision and losses due to the measurement resistance. With this solution it is necessary to adapt the measuring device to each use.
• FIG. 1 illustrates this solution.
• a main conductor 101 crossed by a current to measure Iprim The main conductor passes into a magnetic torus 102 whose role is to concentrate the field lines created by the passage of current Iprim in the main conductor 101.
• a patch 103 Hall effect is included in an air gap in the magnetic circuit.
• the Hall effect pellet creates a voltage Vh proportional to: the magnetic flux density B, the current Ic, and a constant called Hall constant.
• This voltage Vh is amplified by an amplifier 104 and converted into a proportional current Is.
• Figure 2 illustrates a generic embodiment of the invention.
• Figure 2 shows a magnetic torus 201 characterized by its geometric dimensions, the effective length, and Ae its effective area.
• B is the flux density in the magnetic material, / - / is the magnetic field.
• FIG. 2 also shows a primary conductor 202 in which a current Iprim flows. This driver performs Nprim turns around the torus. In the example of Figure 2 Nprim is 1
• the square signal voltage generator 204 supplies a square voltage Vosc which switches between the + E and -E voltages.
• the role of this generator is to alternately carry the magnetic material in saturation of + Bsat to -Bsat (the magnetic flux density excursion)
• this average current Isec is extracted, which makes it possible to deduce the value of the current to be measured Iprim.
• the extraction is carried out by integrating the current Isec.
• the invention therefore relates to a current sensing device characterized in that it comprises: - a magnetic core
• a measurement resistor connected between the electrical mass and a second terminal of the secondary winding via an extractor circuit.
• the device according to the invention is also characterized in that the magnetic core is of fine section, of the order of one micrometer.
• the device according to the invention is also characterized in that the number of turns of the primary winding is 1, that is to say that it is a simple wire passing through the magnetic core.
• the device according to the invention is also characterized in that the number of turns of the primary winding is strictly greater than 1.
• the device according to the invention is also characterized in that the number of turns of the secondary winding is of the order of a thousand.
• the device according to the invention is also characterized in that the extractor circuit is an integrator circuit whose inputs are for one the electrical ground, for the other the terminal of the secondary winding to which is connected the measuring resistance, the output of the integrator circuit being connected to the terminal of the measuring resistor which is not connected to the secondary winding.
• Figure 1 an illustration of a sensor of the state of the art.
• Figure 2 an illustration of a generic sensor according to the invention.
• Figure 3 an illustration of a practical implementation of a sensor according to the invention.
• Figure 4 an illustration of a physical embodiment of a magnetic core according to the invention.
• Figure 5 a correlated illustration of the evolution of Vosc, Vsec, Iphm and Vint signals over time.
• This conductor is a primary winding crossed by a current Iprim which must be measured.
• the core 301 has a micrometric section, a few tens of micrometers.
• Figure 4 illustrates such a torus.
• Figure 4 shows the conductor 302 which passes through a central orifice, a torus 401 mechanical square section. In practice this section could be other, circular or rectangular for example. Torus 401 is hollowed at its center by an opening 403.
• the torus 401 is formed of several elements.
• the torus 401 comprises a support 402 which is formed in a non-magnetic and electrically non-conductive substrate.
• the support 402 therefore has a crown section.
• the torus 401 also has, on at least one of its faces, near the opening 403 a closed magnetic loop 404 of micrometric dimensions, a few tens of micrometers in practice.
• This loop 404 is made in an electromagnetic material deposited on the support 402 by a micrometric screen printing process, the most common of these methods being:
• the torus 401 further comprises, deposited on the loop 404 an insulating layer 405 of a few microns to a few tens of microns thick.
• This insulating layer is produced by a micrometric screen printing process, the most common for this operation being: photo lithography for polymer type insulators, or
• metal oxides for example SiO 2 or Al 2 O 3.
• the torus 401 finally comprises, wound around the torus 404 a winding 406 of turns, corresponding to the secondary winding of the invention, also produced by a micrometric screen printing method of the type used to make the torus 404.
• winding 406 has two ends 407 and 408 to which the other elements of the sensor according to the invention are connected.
• the set of cores 402, 404, 405 and 406 is covered by a protective mold 409 such that said molding isolates the cores said cores leaving free the opening 403 and leaving accessible the ends 407 and 408 to be able to connect them other elements of the invention.
• FIG. 3 shows that the end 407 is connected to an oscillator circuit 303 and that the end 408 is connected to an integrator circuit 304.
• FIG. 3 shows that the oscillator circuit 303 comprises an operational amplifier 305.
• This operational amplifier 305 comprises:
• the input 306 is connected to an electrical ground 31 1 via a resistor R1.
• the input 306 is connected to the output 310 via a resistor R2.
• the input 307 is directly connected to the end 408.
• the input 308 is connected to a potential + E.
• Input 309 is connected to a potential -E.
• the output 310 is connected to the end 407.
• FIG. 3 shows that the integrator circuit 304 includes an operational amplifier 312.
• This operational amplifier 312 comprises: a non-inverting input 313,
• the input 314 is connected to the end 408 via a resistor Rint.
• the input 314 is connected to the output 315 via a capacitor Cint.
• the output 315 is connected to the end 408 via a resistor Rsense, which is the measurement resistor.
• the circuit 303 is an autonomous voltage oscillator. It is a comparator whose 307 inverting and 306 non-inverting inputs oscillate between E and -E. The positive reaction of the system is ensured by the loopback of the output on the non-inverting input by a gain G ⁇ 1. It is recalled here that in the case of this arrangement the gain G is R1 / (R1 + R2).
• the voltage oscillator is a comparator whose output voltage can vary between + E and -E. This voltage circulates a current Isec in the winding 406. This current leads to saturation of the magnetic core. The voltage Vsec, increases until reaching the voltage
• N sec-Ae - ⁇ B Figure 5 also illustrates the voltage Vsec as a function of the evolution of
• the voltage Vsec follows, with a deformation due to the magnetic core, the voltage Vosc.
• the voltage Vosc has a zero average value, except during a current variation in the conductor 302. In this case the voltage Vsec is disturbed and then restored to its stable form following the action of the integrator circuit 304.
• the circuit 304 is a looped system consisting of a comparator and an "integrator" gain function K i which makes it possible to extract the image from the average value of the Iprim current, ie the potential Vint.
• This voltage is fed back to Rsense, which makes it possible to control the oscillation at the center of the hysteresis cycle by compensating for the imbalance created by the ampere-turns of the primary current.
• the gain Ki is 1 / (Rint * Cint).
• Diagrams 502 and 503 of Figure 5 show the effect of a current step Istep on Vsec.
• the average value changes, until the compensation loop reacts and refocuses (T1) the average value of Vsec on Ovolts by injecting a voltage Vint.
• the value of Vint is then a direct image of the current to be measured Iprim by fundamental relation
• the sensor according to the invention makes it possible to achieve higher accuracies than the other measurement methods.
• the accuracy of the measurement is essentially related to the accuracy of the Rsense resistance. It is a low power resistor, which can be easily found in accuracies of the order of 0.1%, and with a low sensitivity to temperature conditions.
• the principle of compensation of ampere turns with an integrator makes it possible to extract and to measure with a null error. The ampere turns are compensated directly and not an image of these through an intermediate sensor which induces an error.
• the dynamics of the sensor is related to the speed of the hysteresis cycle.
• the law of faraday imposes an effective section of the toroid of a few tens of micrometers. This is made possible thanks to a screen printed magnetic circuit. We can then obtain a bandwidth> 100Khz.
• the transformer effect guarantees good linearity.
• the integrator ensures that there is no offset effect near the current zero.
• the sensor according to the invention therefore has all the desired benefits.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)
• Measuring Magnetic Variables (AREA)
• Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
• Secondary Cells (AREA)
• Ignition Installations For Internal Combustion Engines (AREA)
• Level Indicators Using A Float (AREA)
• Measurement Of Current Or Voltage (AREA)
• Transformers For Measuring Instruments (AREA)

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Citations (7)

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• 2007
  • 2007-07-19 FR FR0756599A patent/FR2919068B1/fr not_active Expired - Fee Related
• 2008
  • 2008-07-10 BR BRPI0814264-5A2A patent/BRPI0814264A2/pt not_active IP Right Cessation
  • 2008-07-10 RU RU2010105843/28A patent/RU2431851C1/ru not_active IP Right Cessation
  • 2008-07-10 DE DE602008004535T patent/DE602008004535D1/de active Active
  • 2008-07-10 JP JP2010516554A patent/JP2010533856A/ja active Pending
  • 2008-07-10 CN CN200880105466A patent/CN101796421A/zh active Pending
  • 2008-07-10 US US12/669,560 patent/US8773112B2/en active Active
  • 2008-07-10 AT AT08827954T patent/ATE495453T1/de not_active IP Right Cessation
  • 2008-07-10 EP EP08827954A patent/EP2171483B1/fr active Active
  • 2008-07-10 WO PCT/FR2008/051298 patent/WO2009024692A1/fr not_active Ceased
  • 2008-07-10 CA CA2707102A patent/CA2707102C/fr not_active Expired - Fee Related

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