GB710764A - Improvements in and relating to electric control systems - Google Patents

Abstract

710,764. Control of motors. BRITISH THOMSON-HOUSTON CO., Ltd. July 24, 1951 [July 26, 1950], No. 17499/51. Class 38(3) [Also in Group XXXV] The current supplied from a constant voltage source 4 to the separate field winding 3 of a motor having an armature 1 is kept constant at any value to which it is adjusted by connecting an amplidyne, the secondary armature reaction of which is undercompensated, in the field circuit of the motor. As shown, the amplidyne operates throughout its working range solely as a stepdown machine, the voltage at brushes 5, 6, never being reversed. A stator winding 9 of the amplidyne is energized in accordance with the voltage across brushes 5, 6, and operates to reduce the short-circuit current of the brushes 7, 8. A stator winding 11 opposes the winding 9 and is adapted to prevent the latter from producing excessive flux along the short-circuit axis when the voltage at brushes 5, 6, is substantially equal to the internal voltage-drop of the amplidyne (i.e. corresponding to full field operation of the motor). The current applied to the motor field winding 3 is substantially proportional to that flowing in the control field winding 12 of the amplidyne. The latter winding is supplied from the constant voltage source 4 through potentiometer 13, 14, and in series with the winding are connected a rheostat 17, a fixed resistor 18 (the ohmic value of which is much greater than that of the winding 12) and a portion of resistor 19 which has a sliding contact 15 in common with potentiometer resistor 14. The winding 12 is constructed of material having a small temperature coefficient. Adjustment of the rheostat 17 allows fine regulation of the speed of the motor, separate from the regulation provided by the slider 15. An additional winding 22 on the same axis as the winding 12 regulates the degree of compounding of the motor 1. The winding 22 is energized through potentiometer 23, which is adjusted in common with the contact 15, in accordance with the armature current of the motor 1. In a multi-motor drive, the sliding contacts 15 may be adjusted together by means of servomotors and a common controller, the individual speed-regulation of each motor being effected by means of the rheostats 17. By modifying its stator windings the amplidyne may be operated solely as a booster.