GB253650A - Improvements in dynamo electric machinery - Google Patents

Abstract

253,650. Burleigh, J. W. April 8, 1925. Exciting.-In a variable-speed, constant-volts continuous-current generator having a doublywound armature with two commutators, the fixed windings are connected between one main brush and a subsidiary brush, both of which bear on the same commutator, the main brush being at the usual commutating position and the subsidiary brush being displaced therefrom. The two armature windings may be connected in series or in parallel. In the form shown in Fig. 1, a double armature bipolar machine with commutating poles 9 has a commutator 2 to which the main load 8 is connected and a second commutator 1 for exciting the fields, one of the exciting brushes 5 being displaced from the neutral position. The field coils 3 may both be connected to one pair of brushes 4, 5 in series, as shown, or two separate coils may be used, each connected to its own main and subsidiary brushes. In the form shown in Fig. 2, three brushes bear on the commutator 1, two of which, 4, 12, in the usual commutating position supply an external load 13 while the fields 3 are excited from the main brush 4 and a displaced auxiliary brush 5. The Specification describes also an arrangement in which the main load is supplied by both armatures in series while the fields are excited partly from an external source and partly by a coil connected between a displaced auxiliary brush on one commutator and one main brush on the same commutator. The partial excitation of the fields by an external source may be applied to any of the forms described. A commutating notch may be formed in the pole-face adjoining the brush 5 and neutralizing coils may be wound around a half of each pole face. Alternatively, the neutralizing coils may embrace the commutating poles, as shown at 15 in Fig. 5, or they may be extended further so as to spread from the central notch in one main pole to that in the next and enclose the commutating poles at their mid-points.