GB894275A - Improvements in and relating to electric follower motor control - Google Patents

Abstract

894,275. Electric correspondence control systems. LICENTIA PATENT - VEKWALTUNGS-G.m.b.H. Aug.26, 1960, No. 29544/60. Class 40 (1). A selsyn system for controlling, e.g., the screw-down gear of a rolling-mill, comprises a plurality of selsyn units selectively connectible for determining the displacement of a servomotor as measured from either the last position, or a fixed zero position. As shown, a receiving selsyn 11 with A.C.-energized single-phase rotor, has its 3-phase stator winding connected via switch 42 and differential selsyn 13 to the stator of a selected transmitting selsyn 15a- 15n. If the angular position of the rotor of selsyn 11 does not agree with that of the manually-adjusted rotor of the selsyn 15a-15n selected by operation of switches 14a-14n, 14a<SP>1</SP>-14n<SP>1</SP>, a signal voltage is developed in the latter rotor which is amplified at 16, 17 to rotate motor 10 and selsyn 11 until agreement is reached. The error signal is also fed through an amplifier 23 to a first relay which operates switch 24 to transfer motor 10 to manual control at a predetermined low value of error signal, and also to a second relay which closes switches 14, 14<SP>1</SP> to compare the new position of selsyn 11 with a further selsyn 18, the difference signal being fed via amplifiers 19, 20 and motor 21 to the rotor of differential selsyn 13. Thus the combined output from selsyns 11, 13 is again zero, and any transmitting selsyn subsequently connected will determine the displacement of motor 10 from this new zero. To revert to the original zero, switch 42 is operated via selector switch 22 to replace selsyn 11 by a further, preset selsyn 43, whereupon motor 21 drives the rotor of differential selsyn 13 to its initial position. Selsyn 18 is automatically disconnected at switches 14, 14<SP>1</SP> when its output signal is zero.