News Column

Patent Issued for Current Sensor

July 23, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Rousset, David (Toulouse, FR); Davy, Arnaud (Pechbonnieu, FR), filed on July 10, 2008, was published online on July 8, 2014.

The patent's assignee for patent number 8773112 is Airbus Operations SAS (Toulouse, FR).

News editors obtained the following quote from the background information supplied by the inventors: "The aspects of the related embodiments relate to an improved insulated current sensor and adapted to slave power electronic devices for onboard avionics.

"The domain of the disclosed embodiments is that of current sensors. More specifically, the domain of the disclosed embodiments is that of slaving/controlling power electronic devices that are developed mainly in the aeronautics, automotive, rail, and energy industries. In such electronic systems, the measurement of the physical quantities 'current' size is effectively a control variable to be measured in order to control the device."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "A goal of the disclosed embodiments is to provide a sensor for the avionics environment, particularly a sensor that supports an important variation in temperatures.

"Another goal of the disclosed embodiments is to provide a sensor with a wide range of use.

"Another goal of the disclosed embodiments is to provide a sensor with good linearity.

"In the prior art, there are several devices that are used to measure currents and that are integrated into the control loops of electronic devices.

"The most obvious way to measure a current is that of a shunt resistor, which involves using in parallel a low value resistor and measuring the voltage at the terminals. Simple in appearance, this method is not entirely satisfactory.

"The currents to be measured flow through high-voltage (hundreds of volts) conductors, and it is not easy to extract this measurement and restore the electrical ground.

"An insulated amplifier is often required. The associated electronics is then quickly complicated (secondary power supply referenced to the potential of the conductor, transformer).

"A resistor is a high heat dissipation component. To measure a current, a low-value current is generally chosen in order to minimize losses by dissipation, but this also comes as a disadvantage because very low voltage levels have to be measured (around a few millivolts) for low currents, which causes a significant loss of accuracy. It then becomes necessary to find a compromise between accuracy and losses due to the measuring resistor. With this solution, the measurement device must be adjusted to each use.

"Another solution from the prior art is to measure the current by the closed loop Hall sensor method. FIG. 1 illustrates this solution.

"That is, a main conductor 101 is traversed by a current to be measured Iprim. The main conductor passes through a magnetic core 102, whose role is to bring together the field lines created by passing the current Iprim through the main conductor 101.

"A Hall-effect chip 103 is included in an air gap in the magnetic circuit. The Hall-effect chip creates a voltage Vh proportional to the magnetic flux density B, the current Ic, and a constant called the Hall constant. This voltage Vh is amplified by an amplifier 104 and converted into a proportional current Is.

"A secondary coil 105 with Ns turns receives the current Is. This is called a compensation coil, because traversed by the current Is, it opposes the ampere-turns created in the magnetic core by the main conductor in order to have: Ns*Is-Nprim*Iprim=0

"The final Vsense expression measured at the measuring resistor 106 terminals and based on the Iprim quantity is: Vint=Rsense(Nprim/Ns)Iprim

"These Hall-effect sensors have limitations, however, making their use complex in some environments. Some of these limitations include the following: A risk of magnetic offset in the event of an overcurrent. This overload can lead to accidental saturation due to the residual field from the magnetic material. This adversely affects the accuracy of the sensor. It must then be demagnetized. Frequent maintenance for this is therefore necessary. Generally, the sensor is highly sensitive to temperature variations. The computing constant relating the field B to the voltage Vh in the Hall-effect cell varies according to the temperature. The cell also causes offset voltages, causing inaccuracies in the vicinity of the zero current.

"The disclosed embodiments will be better understood upon reading the following description and studying the figures that accompany it. They are presented for illustrative purposes and are not limiting to the disclosed embodiments. The figures show:

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1: An illustration of a sensor from the prior art.

"FIG. 2: An illustration of a generic sensor according to the disclosed embodiments.

"FIG. 3: An illustration of a practical implementation of a sensor according to the disclosed embodiments.

"FIG. 4: An illustration of a physical realization of a magnetic core according to the disclosed embodiments.

"FIG. 5: A correlated illustration of changes in Vosc, Vsec, Iprim, and Vint signals over time.

"FIG. 6: A schematic illustration of a generic sensor according to the disclosed embodiments."

For additional information on this patent, see: Rousset, David; Davy, Arnaud. Current Sensor. U.S. Patent Number 8773112, filed July 10, 2008, and published online on July 8, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8773112.PN.&OS=PN/8773112RS=PN/8773112

Keywords for this news article include: Airbus Operations SAS.

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Source: Journal of Engineering


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