GB465527A - Improvements in electric motor control systems - Google Patents

Abstract

465,527. Control of two D.C. motors. ENGLISH ELECTRIC CO., Ltd., CARNEGIE, H. S., and ROGERS, A. E. Nov. 16, 1935, No. 31788. [Class 38 (iii)] Varying E.M.F.-A motor driving a reel on which stripe material is coiled on itself, and operating normally as a purely series-wound motor, is supplied from a source including one or more generators so excited in accordance with load that the voltage applied'to the motor decreases in proportion to any increase in the load current taken thereby, and the strip tension remains constant. A rolling mill drives a generator 1, Fig. 1, having a separately excited field 2 opposed by a series field 3, the generator supplying the series-wound reel motor 4 on which the roller material is wound. The generator field 2 is controlled by resistances 8, 9, whereby the tension maintained in the rolled material may be adjusted, and inching of the motor 4 effected. The torque of the motor 4 may be maintained at standstill by a generator 11 connected in series or in parallel with the generator. The motor 4 may be provided with a field winding 12 whereby electric braking may be effected when the generator field 2 is deenergized, and this field 12 may be used at starting. In a modification, the generator 1 has a single field supplied from an exciter on which the fields 2 and 3 are provided. In a further modification, the generator 1 is driven not by the mill but by independent means, and the exciter provided with the field windings 2, 3 is driven by the mill. In this further modification, the motor torque at standstill is obtained by providing the generator 1 with a field winding additional to that supplied from the exciter. The generator may also have a series " suicide " winding. Where the mill driving motor and the reel motor 4 are supplied from a Ward-Leonard generator 26, Fig. 4, the generator 1, excited in the same manner as in the system shown in Fig. 1, or from an exciter, coupled to the mill, is connected in series with the motor 4. The generator fields 2, 3 in this arrangement may assist or oppose but the field 3 produces a voltage in the generator 1 opposing the voltage of the generator 26. A similar arrangement may be used when the motor 4 is supplied from a constant voltage source, suitable starting means being provided for the motor. When the generator 1 is provided with an additional field winding to obtain a torque from the motor 4 at standstill, this field winding may be excited to an extent weakened by resistance during normal running, and may be employed for inching.