GB711104A - Improvements in or relating to control systems for electric motors - Google Patents

Abstract

711,104. Control of several D.C. motors IGRANIC ELECTRIC CO.. Ltd. July 4, 1952 [July 19, 1951], No. 16882/52. Class 38(3) A system for applying stalled tension to a strip of material 10 passing from rolls 11, 12, to a reel 13 comprises a reel motor 19 supplied from generafor 21 which is excited in accordance with the speed of roll motor 14, A generator 17 with a field winding 17a energizes the roll motor. An exciter 27 has a control field winding 33 responsive to the armature current of the motor 19, and is connected in the field circuit of the reel motor in bucking relation to a constant source 15, so that a tendency for the armature current to increase as the diameter of the reel 13 becomes larger is counteracted by an increase of excitation of the winding 19a. A rectifier 28 prevents the bucking-action of the exciter 27 from exceeding the predetermined value represented by the voltage-drop across resistor 20. In order to prevent the armature voltage of the motor 19 from reaching zero value when the motor is stationary, the exciter 27 is connected to the field winding 21a of the generator 21. The motor 19 will thus exert stalled torque upon the reel and thereby maintain the desired value of tension in material 10 with the reel at rest. In place of tachometer generator 23, a compound rheostat of the type described in Specification 684,882 having its adjusting element coupled to that of the regulator of the field winding 17a, may be used for supplying the winding 21a with an excitation voltage proportional to the speed of the motor 14, Fig. 3 (not shown). A similar compound rheostat may be connected to the armature of the exciter 27 and with the field winding 21a for supplying the latter with an excitation voltage proportional to the output of the exciter.