Liaisons Electroniques-mecaniques Lem Sa

Liaisons Electroniques-mechaniques Lem S.a.

Marcel Etter

A direct current of high intensity having alternating current components superposed thereon is flowing in a conductor 1 through a magnetic circuit 5, 6. Two measuring coils 7, 8 are arranged inside opposite air-gaps of the magnetic circuit and are connected in an electric measuring circuit in series with each other and in parallel to voltage dividers 12, 13 and 14, 15. The alternating current components induce voltages in the coils 7 and 8 which add up, the sum thereof appearing across the series-connection of resistors 13, 15. This voltage is integrated by an integrating circuit 10 and then filtered in a band-pass filter 11. The magnetic circuit 5, 6 is screened by lateral screening members 30, 31 so that the remaining field lines of a lateral parasitic magnetic field produce in the magnetic circuit flux portions which are approximately equal and which are added to the useful flux in one air-gap and are substracted from the useful flux in the other air-gap.

Inductive measuring device for measuring alternating current components

Bidirectional electric current sensor fed from a unipolar source

Current sensor comprising a magnetic circuit with an air gap

A current measuring device includes first and second current transformers, having each a magnetic core, a primary conductor or winding and a secondary winding coupled with the magnetic core, the primary windings or conductors being connected to carry the current to be measured. The secondary windings of the first and second transformers have an equal number of turns and are connected in series with each other, and arranged so that the currents induced in the secondary windings by the current to be measured flow in the same direction. A current generator has an output connected to the secondary winding of the first current transformer for feeding to the same a current comprising a magnetizing current component capable of driving the corresponding core, alternately, in opposite states of saturation. A device is provided for controlling the generator by the magnetizing current component, and measuring device are provided for measuring the current flowing in the secondary winding of the second current transformer, which is proportional to the current to be measured.

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Troinex, Switzerland

Marcel Etter