Patent GB-469958-A (GB)
Title: Improvements in and relating to electric motor control equipments
IPC: B60L15/10
Filed: 1936-02-03
Abstract: 469,958. Control of D.C. motors; controllers. GRAY, W. T., and METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. Feb. 3, 1936, No. 20650/37. Divided out of 470,065. [Class 38 (iii)] Armature and field control; combination of resistances.-A resistance is divided into a number of sections adapted to be connected first in the armature circuit of a series motor and then across its field, switching means being provided which first places the resistance sections in a single path connection or one having relatively few paths, and subsequently in a series of multiple path connections, the switching means exerting its control on the resistance in both the armature and field circuit control stages. The switching means may comprise a drum controller actuated manually or by a servomotor as described in Specification 451,514. The tapping connections D, F, H, J, L, of a resistance AM pass through a switch in each to a conductor B1, while a second set of tappings B, C, E, G, I, K, intercalated with the first set pass through respective switches to a conductor B2 in which further switches may be interposed between some of the successive tappings. Motors M1, M2 are first connected to the supply in series with the resistance AM by closing switches R1, F2, and line switches LS1, LS2, and then the resistance is removed in steps by closing switches R2-R16 in sequence, the switches R5, R6 closing simultaneously on the fifth notch and the switches R8, R9, R11, R12, and R14, R15 closing in pairs on the seventh, ninth and eleventh notches respectively. Thus on the twelfth notch the motors are connected with the resistance section r12 only. At the thirteenth notch the switches R5, R8, R11, R14, and R17 are closed to connect the resistance sections r1-r11, in series across the resistance section r12, and on subsequent notches the switches R2, R3, R6, R9, R12 and R15 close to remove the resistance sections r1-r10, leaving the sections r11, r12, connected in parallel. On further notches the sequence is repeated in turn until at the sixty-fifth notch the resistance sections r3-r12 are all in parallel. The sequence may be continued to include the sections r1, r2. On the sixty-sixth notch the switch R1 is closed to short-circuit the resistance completely. A switch F1 is then closed followed by the opening of switches F2 and R2-R17, and by closing the switch F3, the resistance AM is connected across the motor fields Fd1, Fd2. The resistance is then varied as before. The resistance sections may be graded and some notches may be omitted if desired. With a drum type of controller the contact fingers are divided into two groups of adjacent fingers associated respectively with the two sets of alternate tappings and interlacing of connections in the drum thereby avoided. In passing to the field weakening notches the alternative circuits are established before the opening of circuits at the drum. The 'arrangement is applicable to a seriesparallel control system. The drum controller may be built up in units, and additional switches may be directly associated with the drum as in the arrangement according to the invention described in Specification 470,065.