GB578128A - Improvements in dynamo-electric machines for the remote transmission of angular motion and torque - Google Patents

Abstract

578,128. Electric distant control systems. BRITISH THOMSON-HOUSTON CO., Ltd. CHOUDHURY, S-U. A,, MAGGS, A. H., and CLARK, L. J. Jan. 24, 1944, No. 1315. Addition to 578,122. [Class 40 (i)] [Also in Groups XXXV and XXXVII] Specification 578,121 describes a selsyn transmitter in which the alternating supply current is fed through brushes to commutated selsyn windings from which currents are derived to control a selsyn receiver. The parent Specification shows how this transmitter can be made to run as a motor, by provision of suitable stator windings. The present invention uses a pair of brushes, in quadrature with the above brushes, connected by a choke, thereby to ensure that the motoring field coincides with the selsyn field, so that accurate synchronism between transmitter and receiver is maintained on motoring. In the Figure, brushes B, D, feed the selsyn coils of the transmitter via the commutator (segments not shown) on the armature 1 and currents to be fed to the receiver coils 3 are derived from slip rings connected either to equally spaced tappings on the selsyn coil or to suitable secondary coils deriving currents therefrom. The transmitter can be made to run in either direction as a motor by closing the reversible switch 22, which connects alternating current supply, via a suitable power factor and speed controlling network to the stator coil 12 whose axis is in quadrature with axis B-D. The distortion of the field so produced is counteracted by flux produced in the quadrature axis by current in the armature taken by the choke 25 from the brushes A C. Vector diagrams in Figs. 2, 3 and 4 (not shown) demonstrate that the system is stable under no-load conditions and that on load there is a tendency for speed to increase with load. By suitably choosing components this may be used to counteract the losses which normally in practice increase with load, to cause the speed to be substantially independent of load except at very low speeds when it is necessary to introduce a stator wind- :ng 14 in the axis B-D. fed with demagnetizing current in order to effect stability.