GB819033A - Improvements in electrical resistance switching networks - Google Patents

Abstract

819,033. Control of D.C. motors; controllers. GENERAL ELECTRIC CO. Nov. 16, 1955 [Nov. 16, 1954], No. 32847/55. Class 38 (3). A resistor for controlling an electric motor has a plurality of sections A-H connected in series with voltage taps 11-18 therebetween, a pair of bus wires 23, 24, being connected respectively to one end of the resistor and to a voltage tap 11 adjacent said end and being adapted to be connected to the remainder of the voltage taps in a predetermined manner. Contactors 1, 2 are provided for connecting each of the bus wires to a load circuit and a switch 31 connects the other end of the resistor to the circuit, whereby the making and breaking of the connections between the bus wires and the voltage taps varies the effective resistance. The section A is short-circuited by moving controller 25 from the first to the second notch, and, on the third notch, sections A and B are connected in parallel with each other and in series with the sections C-H. In moving to the fourth notch, the sections A and B are short-circuited. Sections A, B and C are connected in parallel on the fifth notch, and are serially-connected with sections D-H. Proceeding to the sixth notch shunts sections A, B and C. On the seventh notch, sections A and D are connected in parallel, and this combination is placed in series with sections E-H. Movement to notch 8 puts sections A, B, C, D in parallel with one another and in series with sections E-H. Proceeding to the ninth notch causes the sections A, B, C, D to be short-circuited. This sequence of operations is continued until the whole of the resistance is removed in the thirty-first position of the controller 25, Figs. 2, 3 (not shown), the arrangement being such that none of the contactors 1-9 are opened whilst carrying current. In a modification, some of the notches are omitted to shorten the sequence and to make the changes of the resistance more closely approach a geometrical progression. As shown, the resistance is used for controlling series motors 19, 20, the selector switch 31 allowing the resistance to be connected for accelerating the motors, for dynamic braking, or for field regulation. Specification 692,099 is referred to.