GB890411A - Improvements relating to the measurement of electro-magnetic power - Google Patents

Abstract

890,411. Measuring flux leakage from magnetic cores. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Oct. 21, 1958 [Sept. 30, 1957; June 6, 1958], Nos. 30548/57 and 18191/58. Class 37. In an arrangement for measuring the magnetic leakage flux from a magnetic core 1 having A.C. windings; a Hall plate, having a pair of current input electrodes 7, 8, and a pair of Hall voltage output electrodes 3, 4, is positioned in the leakage flux; the flux lines of force extending at right angles both to the direction of current flow between electrodes 7, 8 and also to the line joining the electrodes 3, 4; an input current proportional to the flux leakage is applied to electrodes 7, 8; and the component of the Hall voltage at the second harmonic of the A.C. supply to the core windings is measured. Electrodes 7, 8, on faces 9, 10 of the Hall plate, are connected to the ends of a loop embracing the transformer core 1, whereby an E.M.F. is applied across faces 9, 10 which is proportional to the varying core flux; faces 5, 6 of the Hall plate are connected by electrodes 3, 4 to an amplifier 11 which selectively amplifies the Hall voltage component of the second harmonic of the A.C. supply to the core windings; this component being proportional to the product of the magnetic leakage field through the Hall plate and the current flowing between faces 9 and 10 due to the applied E.M.F. In a second embodiment, Fig. 2 (not shown), the input current applied to electrodes 7, 8 is provided by the output of an amplifier, the input to which is obtained from two antennae having their ends positioned adjacent the faces 9, 10 of the Hall plate.