Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Thermal
Patent
1998-10-14
2000-09-19
Metjahic, Safet
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Thermal
324105, G01R 526
Patent
active
061217662
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to current sensor assemblies of planar form arranged for connection in series with an electrical circuit, the assembly including a first conductive member adapted to contact a first conductor in the circuit, a second conductive member adapted to contact a second conductor in the circuit, a third member of conductive material connected at one end to the first conductive member and at its other end to the second conductive member such that current flow in the circuit between the first and second conductors is via the third member, third member being arranged so that the temperature rise at different parts of the member caused by current flow through the layer is different, the assembly including a plurality of temperature sensors located to sense the temperature of the third member at the different parts, and the assembly providing an output representative of current from the outputs of the temperature sensors.
There are many applications where it is desirable to monitor current in electrical equipment and systems. Knowledge of current and power consumption can enable power supply to be managed in the most effective way and can enable the detection of faults. Although current sensors are available, they are generally expensive and bulky. In FR-A-548895 there is described a current sensor having a self-supporting conductive strip extending between two terminals, the resistance of the strip being measured as its temperature changes under the effect of current flow.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved current sensor assembly.
According to the present invention there is provided a current sensor assembly of the above-specified kind, characterized in that the third conductive member is a thin planar layer supported along its entire length by a support and at least a part of the support in contact with the planar layer is electrically insulative.
Parts of the support are preferably of different thermal conductive at different points along the length of the planar layer so that heat dissipation is different at the different points. A part of the support may be diamond. The first and second conductive members may be planar members located on opposite sides of the assembly. The sensor assembly may have an aperture extending through the first and second conductive members and adapted to receive a terminal post projecting from the first conductor, the second conductive member being electrically insulated from the terminal post by an electrically-insulative collar in the aperture. The sensor assembly may include three temperature sensors, the planar layer of conductive material being arranged so that the temperatures t.sub.1 and t.sub.2 at opposite ends are less than the temperature t.sub.3 at a point between its ends, the assembly including a circuit for calculating t.sub.3 -(t.sub.1 +t.sub.2)/2 and for deriving an indication of current accordingly. The output representative of current may be provided via the electrical circuit itself.
A current sensor assembly according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of the sensor assembly in a part of a circuit;
FIG. 2 is a cross sectional side-elevation view of the sensor assembly;
FIG. 3 is a plan view of a part of the sensor assembly; and
FIGS. 4 and 5 illustrate alternative ways of deriving outputs from the sensor assembly.
DETAILED DESCRIPTION OF THE INVENTION
With reference first to FIG. 1, the sensor assembly 1 is a tag of planar form and rectangular shape with a circular aperture 2 through its thickness, close to one end. The assembly 1 is secured to a first conductor 3 by means of a threaded terminal post 4 projecting upwardly from an upper surface of the conductor, through the aperture 2. The first conductor 3 is a power line formed by a metal bar of rectangular section having a flat upper surface at
REFERENCES:
patent: 3696294 (1972-10-01), Krupka
patent: 4695793 (1987-09-01), Katzmann
patent: 4789823 (1988-12-01), Delfs et al.
Metjahic Safet
Smiths Industries Public Limited Company
Tang Minh N.
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