GB242705A - Improvements relating to control switches for varying the resistance of a circuit - Google Patents

Abstract

242,705. Cox, F. B. Aug. 12, 1924. Controllers, with combinations of resistances.- Variable resistances, particularly for use with motor starters, comprise the combination of a group of unequal resistances R<1> - - R<4> with another group of resistances R<6> - - R<9>. Switches S<1> - - S<5> adapted to bridge corresponding contacts 2, 3 are operated cyclically so that each resistance R' - - R<4> and each series combination thereof is introduced successively into the circuit, and similar switches S<6> - - S<10> bridging contacts 2<1>, 3<1> cyclically insert the resistances R<6> - - R<9> individually and in parallel combinations into the circuit. The switches can be operated in the desired sequence by cams on a commor. shaft, which can be operated by hand or by a sclenoid and retarded by a dash-pot or a second solenoid sensitive to the back E.M.F. of the motor. The two groups of switches may be replaced by a drum controller. The modes of operating the switches are similar to those disclosed in Specification 227,135, and include the use of electromagnetic switches, the coils of which are energized by contacts on a rotatable disc, and of pneumatic switches with electromagnet cally operated valves. The cam-shaft can also be operated by a float actuated by variation of level of a liquid.