GB741060A - Improvements in electric motor control systems - Google Patents

Abstract

741,060. Control of several motors: BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 15, 1953 [Dec. 17, 1952], No. 31997/52. Class 38(3) A pair of motors M1, M2, for driving the upper and lower rollers of a steel rolling mill nave their armatures connected in series circuit with the armatures of generators G1, G2, G3, the armature of generator G3 . being connected between those of the motors. A pair of auxiliary generators CG1, CG2, have their armatures connected in series with one another and in shunt with the generator G3. Points PI, P2, which normally are at equal potential, are joined by a connection C. If the voltages generated by the auxiliary generators are equal, the circuit remains balanced and the current taken by the motors remains the same. By controlling the auxiliary generators differentially, the currents taken by the motors are caused to differ. In a modification, Fig. 2 (not shown), involving a pair of motors with four generators connected symmetrically in pairs between the motors, a switching arrangement allows the auxiliary generators to be connected in turn across one of the main generators, and another of the main generators to be selectively removed from circuit by means of a short-circuit connection. The field excitation of the auxiliary generators may be controlled to maintain equal voltages, the motor field excitation being regulated to provide equal loading. Alternatively, the auxiliary generator field excitation may be arranged to provide the desired speed matching by voltage control when the motors are lightly loaded, and an overriding load-balance control when metal is in the mill.