GB669696A - Improvements in or relating to control systems for electric motors - Google Patents

Abstract

669,696. Control of D.C. motors. SPERRY CORPORATION. Jan. 3, 1950. [Jan. 14, 1949] No. 125/50. Class 38 (iii). [Also in Group XXXV] In a two-field, reversible, servomotor system, motor control is effected through magnetic amplifiers in two ways according to the amplitude of the control signal, with a smooth changeover. In the first mode of operation, at low control signal amplitudes, the resultant strength and direction of the fields. is varied while the armature current remains substantially constant, and in the second mode,. at large control signal amplitudes the armature current is varied while the field remains substantially constant. General arrangement. The fields 44, 47 and armature 50 of the servomotor are energized respectively from magnetic amplifiers 26, 37, 29 fed with. halfwave rectified A.C. from a source 39. The control windings 35, 35<SP>1</SP> of the field amplifiers are energized differentially from a double triode 20 while the armature amplifier control winding 35<SP>11</SP> is energized unidirectionally from the full wave rectified output of a double triode 22. The magnetic amplifiers are provided with conventional bias windings such as 36 and feedback windings such as. 40, 41 and are of similar construction except that the armature amplifier is bigger and operates with a higher bias, e.g. 100 m.a., compared with say 35 m.a. for the field amplifiers, so that the field amplifiers operate and reach saturation before the armature amplifier. Operation. When a D.C. control signal is applied in parallel to the grids of valves 20, 22. one or the other of the magnetic amplifiers 26; 27 (according'to the polarity of the control signal) quickly saturates fully energizing the corresponding field; Although a small signal has little effect on the armature amplifier the normal, or no signal, standing current causes the armature to rotate. Further increase in control signal causes increase of armature current, while the field amplifier being saturated, the field remains substantially constant. Application., As described, signals from a compass magnetometer 10, or Selsyn connected to a steering wheel, are demodulated to provide the D.C. control voltage and the servomotor operates a rudder or other control surface 51, coupled to a D.C. energized follow-up potentiometer 58 providing displacement feedback. Speed feedback is obtained from a generator 55 coupled to the servomotor.