GB556016A - Improvements in electrical control systems for maintaining predetermined speed relationships between co-operating electric motors - Google Patents

Abstract

556,016. Automatic control systems for multimotor machines, and for dynamos. BRITISH THOMSON-HOUSTON CO., Ltd. March 27, 1942, No. 4084. Convention date, March 29, 1941. [Class 38 (iv)] Speed; voltage. - The individual speeds of driving motors in a sectionalized machine such as a paper making machine wherein changes take place in the length of web between sections, are controlled by tachometer generators which are opposed to a selected portion of the automatically regulated constant voltage of a main generator or exciter and the aforesaid portion may be adjustable to provide " draw " adjustment. Fig. 1 shows potentiometers 48, 54 in parallel with an adjustable portion of a potentiometer 28a across the constant voltage terminals of an exciter 17. The section motors 12, 13 have field windings 12a, 13a each in series with a resistance stack controlled by a regulator 52, 58. The actuating winding 52b of each regulator carries the output of a thermionic amplifier 53 grid controlled by the difference between a voltage rectified from a tachometer alternator 49, 55 and a voltage from the potentiometer 48, 54. The draw adjustment is obtained by moving contact 54a of the potentiometer. The potentiometer 28a is normally controlled and motor-driven to adjust the machine speed. The exciter field is regulated by a voltage controlled resistance stack in its field circuit ; the main generator has a similar regulator but its actuating coil is fed from an amplifier 26 similar to 53 and responsive to potential changes in the lower part of a potentiometer resistance 35 responsive to the difference between the voltage of the generator 14 and the portion of the exciter voltage determined by the adjustment of potentiometer 28a. The grid circuits of all amplifiers comprise a feed back coil on the associated regulator and the secondary winding of a stabilizing transformer 47 associated with the .controlled apparatus. In a modification the potentiometers 48, 54 are connected across the generator and permanent magnet D.C. tachometer generators are used ; in this case the generator is regulated in the same way as the exciter 17 and a manually controlled motor-driven rheostat adjusts the regulated voltage of the generator.