GB668165A - Improvements in and relating to automatic electric motor control systems - Google Patents

Abstract

668,165. Control of several D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. April 1, 1948. [April 3, 1947] No. 9239/48. Class 38 (iii). [Also in Group XXXV] The tension in a steel strip passing from a rolling mill to a reel is maintained constant by varying the excitation of the reel motor to maintain the armature current constant and also by injecting into the field control circuit a voltage proportional to the acceleration of the mill motor. The armature of the reel motor 11 is supplied from a D.C. generator 12 through a resistor 17 so that a voltage proportional to armature current is applied to the control field 16a of an amplidyne 16, the output of which controls a second amplidyne 14 acting as a buck/boost generator in series with the supply to the field 11a of the reel motor. A second field winding 12b on the generator is also energized by amplidyne 14 to provide stalled tension when the motor is stationary. An auxiliary motor 18 has its field in parallel with the field of the mill motor 4 and drives generator 19 having its field in parallel with that of a generator 7 supplying the armature of the mill motor 4, hence any change in the field or armature currents of the mill motor produces a proportional change in the output of generator 19, across which is connected a transformer 21. A voltage proportional to the acceleration of the mill motor is therefore induced in the secondary of transformer 21, and this voltage by opposing the voltage across resistor 17 causes the reel motor to be correspondingly accelerated. In a modification, Fig. 2 (not shown), the auxiliary motor 18 has a constant field excitation, and the armature is in parallel with the mill motor armature, whilst the auxiliary generator 19 has its field connected across the mill motor field regulator 9. In another modification, Fig. 3 (not shown), the transformer 21 is omitted, and the control field of amplidyne 16 is connected to the auxiliary generator 19 through a condenser.