GB532715A - Improvements in electric motor control systems particularly adopted for tension control in strip rolling mills - Google Patents

Abstract

532,715. Electric control systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. July 28, 1939, No. 21933. Convention date, July 28, 1938. [Class 40 (i)] [Also in Groups XXXVII and XXXV] The tension of the material in a strip rolling mill controls the ratio of transformation of a transformer adapted to vary the output potential of a generator affecting the excitation of a motor, the speed of which is controlled to maintain the tension constant (see Group XXXV). A lever 24 carrying a roller which is adapted to deflect a strip 12 passing through rolls 14, 16 is subject to constant fluid pressure in a cylinder 32 and arranged on an increase in strip deflection to rotate a transformer winding 38 in relation to a winding 40 and decrease the ratio of transformation. The current circulating through a rectifier 48 and the field winding 58 of booster generator 60 is thus reduced and the generator voltage falls. With the booster voltage added to the voltage of mains A, B the excitation of the field winding 64 of the motor 20 will fall and the motor speed will increase to restore the strip deflection. Transformers 54, 56 inject voltages into the circuit of winding 58 in accordance with the rate of change of motor current and booster voltage respectively in the sense required to retard such changes. The variable ratio transformer may be of any kind ; the application of an auto-transformer and a transformer with a variable reluctance magnetic circuit are described.