GB715700A - Improvements relating to control apparatus for electric motors - Google Patents

Abstract

715,700. Control of motors. ENGLISH ELECTRIC CO., Ltd. Oct. 10, 1952 [Oct. 12 1951], No 23809/51. Class 38(3) Control apparatus for an electric motor comprises a plurality of switch means associated with the sections of a speed controlling resistor for the motor, some at least of the switch means being operated according to a predetermined time sequence, wherein selector means are provided for selecting the particular switch means at which the time sequence starts without altering the time sequence itself. If the time sequence is required to commence at contactor RC4, the selector means -a switch 15-is set at position 4. Movement of a manually operated speed controller closes contacts MC1 ... MC8, eight contacts only being shown in figure 1, and starts up a motor driven timing device 12 which is effective to momentarily connect the positive bus-bar 10 alternatively to timing bus-bars 13, 14. With contacts MC1 ... MC8 closed contactors RC1 ... RC3 operate in quick succession to cut out portions of the speed controlling resistor, the latter contactor, RC3 being energized over contact b of the selector switch 15. Operation of contactor RC3 closes self-maintaining contacts RC3b and also contacts RC3c which prepare contactor RC4 for operation. When now the timing device 12 operates to energize timing busbar 14 contactor RC4 is energized closing selfmaintaining contacts RC4b and contacts RC4c to prepare contactor RC5 for operation. When timing bus-bar 13 becomes energized contactor RC5 operates and the operation continues until all the contactors are closed when the timing means 12 will be de-energized. The time intervals between the closing of the contactors is governed by the speed of the motor driving the timing device 12 which is in turn governed by the rheostats r1 ... r6 (see Fig. 2). During the closure of contactors RC1 ... RC4 the motor driven timing device runs at full speed, no pre-determined time occurring. When contactor RC4 operates, contacts RC4e close and contacts RC4d open (see Fig. 2). With the selector switch 15a in position 4, as is the switch 15. an eddy current braking coil 16, associated with a disc driven by the motor of the timing device, is energized. over a rheostat 41. the speed of the timing device being thereby controlled. When contactor RC5 operates contacts RC5e close and contacts RC5d open thus the brake coil is now associated with rheostat r2 and so on. Movement of the selector switch permits either of contactors RC3 ... RC6 to be associated with rheostat r1 Thus the acceleration of the main motor may be selected by simply moving the switch 15 to the desired position. In a further embodiment the contactors RC1 &c. may be mechanically operated by a cam system. The invention may be applied to both A.C. and D.C. motors and the speed controlling resistor may be used for dynamic braking. Specification 715,701 is referred to.