Electricity: measuring and testing – Measuring – testing – or sensing electricity – per se – Magnetic saturation
Patent
1997-12-29
1999-12-21
Snow, Walter E.
Electricity: measuring and testing
Measuring, testing, or sensing electricity, per se
Magnetic saturation
324127, 361761, G01R 3300, G01R 1520, G01R 1900, H05K 118
Patent
active
060053836
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a current sensor comprising a magnetic circuit with an air-gap, a winding arranged on this magnetic circuit in which flows an electric current to be measured, a magnetic field detecteur arranged in said air-gap and a support plate bearing an electric circuit arranged for amplifying an output signal of said magnetic field detector.
Current sensors of this type are well known and are being used in many technical applications. However, they do not meet all requirements from the standpoint of bulk and cost price.
The present invention therefore aims more particularly at reducing the bulk of such a sensor as well as the space it will occupy when mounted on an external circuit, and it particularly has for object to provide a sensor of substantially flat shape. Furthermore, the invention has for object to provide a sensor of reduced dimensions in which there exists nevertheless a very weak influence of the circuit in which flows the current to be measured on the measuring circuit, and which also has a good immunity against external electromagnetic fields. An important aim of the invention is further to make possible the manufacture of such a sensor in great series in a very economic and efficient way.
To achieve this, the sensor according to the invention is characterized in that said support plate comprises a main portion and a lateral extension thereof, so that the plate has a cut-away area defined by respective adjacent sides of said main portion and of said extension, the magnetic field detector being mounted on the support plate and the magnetic circuit being fixed to this plate in such a way that the magnetic field detector is placed in the air-gap of the magnetic circuit and the winding is placed, at least partially, in said cut-away area.
According to one embodiment of the sensor, the support plate comprises at least one metallized shielding area connected to the ground potential of the electric circuit, this area having at least one portion extending between the magnetic field detector and said winding. This shielding area can have a portion extending between the support plate and a part of the magnetic circuit. Preferably, such a metallized shielding area is provided on either side of the support plate.
According to a preferred embodiment, the winding is arranged on a substantially rectilinear leg of the magnetic circuit, the air-gap being formed between a lateral surface portion of a free end of this rectilinear leg and a free end of a leg of the magnetic circuit perpendicular to said rectilinear leg.
To make possible the use of a pre-formed winding and the mounting of such a winding on said rectilinear leg of the magnetic circuit, the thickness of the winding in the transversal direction thereof is smaller than the length of the air-gap of the magnetic circuit. Preferably, the winding has a cross-section such that it will be fitted closely around the leg of the magnetic circuit on which it is arranged, if necessary over an electrically insulating tube.
The magnetic circuit is preferably made in the form of a stack of metal sheets, said insulating tube being arranged so as to maintain together the portions of the various sheets forming the leg on which it is arranged, and a portion of the magnetic circuit is mechanically fixed to the support plate so as to maintain together the sheets of the circuit by means of this fixing. The insulating tube can advantageously be made of a heat-shrinkable material.
By these different means, the invention makes it possible to manufacture a current sensor achieving the above mentioned objectives in an optimal way.
The invention will be better understood in the light of the detailed description of an example of embodiment shown in the attached drawing, in which
FIG. 1 is a side view of a current sensor according to the invention;
FIG. 2 is a side view of the same sensor seen from the side opposite to that of FIG. 1;
FIG. 3 is a sectional view along the line A--A of FIG. 1;
FIG. 4 is a simplified electric diagram of a current sensor accor
REFERENCES:
patent: 5552700 (1996-09-01), Tanabe et al.
Laforet Marc
Savary Pierre
Browning Clifford W.
Liasons Electroniques-Mecaniques LEM S.A.
Snow Walter E.
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