GB255984A - Improvements in and relating to dynamo electric machines - Google Patents

Abstract

255,984. British Thomson-Houston Co., Ltd., and Dreghorn, H. May 16, 1925. Alternating-current commutator machines.- An alternating-current commutator motor is provided with a rotor and stator divided into two sections with a separate regulating commutating winding on each section, whereby only a part of the total main flux cuts the commutated coils, giving a reduced voltage per segment and a higher output per pole. In the form shown, the rotor of a variable-speed motor is formed in two sections 1, 2 embraced by a common primary coil 3 fed through slip-rings. Each section carries a regulating winding 6, 5 connected through commutators 8, 7 to secondary coils 12, 11 on the two-part stator. Each core carries half of the total flux so that the volts per segment on the commutators are one half of the value given in the usual arrangement. The brush sets are geared together, for instance by bevel gearing, so that the two sets move together and the two sections of the machine share the load equally. Resistance connections and short-pitch coils may be employed. In a modified form, both cores are embraced by a single secondary winding which is connected in series with both regulating windings. Or, alternatively, the primary and secondary windings embrace both cores and are used with only one regulating winding which is wound on a half or any other fraction of the total core length. In the case of a machine in which the commutator winding is used for power factor improvement, one set of commutator brushes only is employed.