SENSOR FOR DETECTING VERY SMALL CURRENT SUPERPOSED UPON LARGE ALTERNATING CURRENT

摘要

PROBLEM TO BE SOLVED: To provide a sensor which can detect a vary small direct current which flows while the current is superposed upon a large alternating current with high accuracy by completely removing the influence of the alternating current. SOLUTION: In the current sensor for both AC and DC provided with a magnetic detecting element 4 in the very narrow magnetic gap 3 of an annular core 2 having the gap 3, a short-circuiting winding 6 and a magnetic flux change detecting winding 7 are wound around a core 2 and the output of the winding 7 is controlled so that the output can become zero by feeding back the output of the winding 7 to the winding 6. A very small direct current contained in the current flowing to a wire to be measured is detected by accurately making the magnetic flux generated from the core 2 due to the current flowing to the wire to be measured zero with respect to the AC component and only detecting the magnetic flux change generated by the DC component of the current flowing to the wire by means of the element 4.