GB539817A - Improvements in or relating to direction indicating instruments - Google Patents

Abstract

539,817. Earth-inductor compasses; phasedifference measurements. SCOPHONY, Ltd., WIKKENHAUSER, G., and JONES, P. L. F. Feb. 23, 1940, No. 3392. [Class 40 (i)] In an earth-inductor compass in which the phase of the voltage generated in a coil rotating in the earth's field is compared with that generated by a generator rotating synchronously therewith, the generated current is applied to the rotor coil of the phase indicator through a transformer the secondary winding of which rotates with and is connected to the rotor coil. On the vertical shaft 1, Fig. 1, of a motor 2 is a permanent magnet 3 which generates three-phase currents in windings 4, 5, 6, the phase of these currents being independent of the movement of the vehicle to which the windings are fixed. On the shaft 1 are also fixed an earth-inductor coil 7 and a coil 8 connected in series therewith. The coil 8 forms the primary winding of a transformer having a fixed secondary winding 9. The iron core of the transformer is formed by a part of the shaft 1, the magnetic circuit being completed by a stationary outer frame 10. Current from the stationary secondary winding 9 is fed after amplification if necessary, to the phase indicator shown in Fig. 2. This consists of a second transformer having a rotatable secondary winding 11 and a stationary primary winding 12, to which is fed the current from the winding 9, Fig. 1. The secondary winding 11 is connected to an air cored coil 13 moving in the field of three stator windings 14, 15, 16, to which are fed currents from the windings 4, 5, 6 of the generator. The coil 13 takes up a position dependent on the difference in phase between the currents generated in the coil 1, Fig. 1, and in the coils 4, 5, 6, and therefore indicates the compass direction of the vehicle. The iron parts of the transformers 8, 9, 11, 12 may be provided with air-gaps, for example an axial slot, or may be segmented. The rotor coil 13 may be damped by means of a small gyroscope or by immersing the instrument in a damping liquid.