APPARATUS FOR COMPENSATING FOR EDDY CURRENTS PRODUCED IN PARTS OF HIGH ELECTRICAL CONDUCTIVITY ON VEHICLES OR THE LIKE BY THEIR MOVEMENT IN THE EARTH'S FIELD

摘要

1,218,171. Modifying magnetic field. SIEMENS-SCHUCKERTWERKE A.G. 24 July, 1961 [23 July, 1960], No. 26801/61. Heading B7S. In a vehicle or the like provided with compensating windings for compensating for the effect of the vehicle on the earth's magnetic field, a transformer is provided for measuring variations in the current in the compensating windings and applying them, after suitable amplification, to further compensating windings surrounding parts of good electrical conductivity in which eddy currents are induced by movement in the earth's field, the current in the further windings being such as to compensate for the field produced by the eddy currents. In the circuit shown a detector 1 gives an output proportional to the magnitude of the earth's field, and this output is applied as a signal voltage through a pre-amplifier 2 and control unit 3 to a power amplifier 4 which supplies current to the compensating windings 5. This current passes through the primary winding of a transformer 6, the secondary winding of which is connected to a transformer unit 7. The unit 7 consists of a field winding 8, a winding 9 having a negative feedback action, and a measuring element 10 which is preferably a Hall generator. The voltage supplied by the Hall generator 10 is amplified in a pre-amplifier 11 and applied to phase-sensitive rectifier elements 12 and through a variable gain amplifier 13 to a power amplifier 14. The power amplifier 14 feeds compensating windings 15 which surround a plurality of small parts or one large part of material of good electrical conductivity. The current flowing through windings 15 passes through a resistance 16, the voltage across which is applied to the negative feedback winding 9 through a resistance 17. To each field variation and consequently to each current variation in the field compensating channels, i.e. in the primary windings of the transformer 6, there is a particular corresponding current in the windings 15 determined mainly by the voltage across resistance 16 and by the resistance of winding 9 and resistance 17. Three similar circuits are provided, one for each co-ordinate axis.