GB835734A - Improvements in control systems for electric motor equipments - Google Patents

Abstract

835,734. Control of two D.C. motors. BRITISH THOMSON-HOUSTON CO. Ltd. Sept. 18, 1956 [Sept. 22, 1955], No. 27099/55. Class 38 (3). The top and bottom rolls of a rolling mill are driven by motors 1, 2, which are supplied from a common source such as a variable-voltage generator. The motors are separately excited by field windings 25, 26 respectively energized by main exciters 27, 28, the exciter 27 having a series field winding 29 and a field winding 29<SP>1</SP> carrying the armature current of the machine 28. This machine is similarly provided with field windings 30, 30<SP>1</SP>. A pilot exciter 36 supplies, in parallel, the field windings 37, 38 of the main exciters, a rheostat 39 differentially adjusting the currents passing through these field windings. The exciters are of sufficient capacity to provide rapid changes in the excitation of the motors whereby to obtain a high rate of change of speed, the pilot exciter having a reference field winding 40 opposed by a feedback winding 35 to prevent the motors from being over-excited. A current-measuring reactor 31 is controlled jointly by the currents in the motor field windings 25, 26, and the A.C. windings of the reactor are connected in series with the feedback winding 35 through rectifier 33. The field currents of both motors may be supplied from one only of the main exciters; and, when a single exciter is in operation, the field currents of both motors pass through the control windings of the reactor so that the feedback current is still dependent upon the total excitation of the two motors.