GB237188A - Improvements in electric motors - Google Patents

Abstract

237,188. Fairweather, W. C., (Underwood Typewriter Co.). Aug. 1, 1924. Motors, controlling; exciting; field magnets; commutating poles; alternating-current commutator machines.-A motor convertible for use with continuous or with alternating current of different voltages or frequencies comprises a number of field coils 49 - - 52 and auxiliary coils 66 - - 73 on a core 58, the auxiliary coils being in series with the armature and arranged, when used with alternating current, to oppose, the field coils and thereby limit the speed of the motor, and a reluctance is placed in the magnetic circuit around the auxiliary coils by the provision of air gaps between the core 58 and iron loops 75 through which the flux is directed, as shown in Fig. 3, or by placing copper bands 125, Fig. 18, on the loops. The loops 75 are secured by straps 80 and are spaced from the main core by wood blocks 78, replaceable by others of different thickness. The main core is formed of quadrants, each end of which forms one-half of either a main pole 53 extending nearly around the armature, or of a commutating pole 65 the two parts of which are secured together by copper clips 64 enclosing laminated iron 64<a>. All the coils are wound separately and are threaded on the quadrants of the core, and the ends of each coil are brought out to a terminal board 83, Fig. 2, where the coils, the armature, and resistances in series with the armature may be connected in various ways to adapt the motor by fixing interchangeable and removable contact panels 96 to the terminal board. The contacts 93 on the different panels are connected together in various ways by wires 95, and the panels are secured with a cover 86 by screws 99. Fig. 7 shows diagrammatically the connection of the terminals to the coils, the armature 41, and resistances 102 - - 105 in series with the armature, the number of resistances cut in being suited to the voltage. The connections shown in Fig. 7 provide for low-voltage continuous current, all the resistances being cut out, and the field coils 49 - - 52 being arranged in semi-parallel, and the auxiliary coils 66 - - 73 arranged similarly. For continuous and alternating current, the auxiliary coils are arranged to assist and to oppose the field coils respectively. Several diagrams are given showing the connections for adapting the motor to different conditions.