GB491743A - Improvements in and relating to direct current dynamo electric machines - Google Patents

Abstract

491,743. Exciting dynamo-electric machines. JUHLIN, G. A., HILL, E. P., and METROPOLITAN - VICKERS ELECTRICAL CO., Ltd. April 21, 1937, Nos. 11422/37, 16056/37, and 1530/38. [Class 35] A machine has an auxiliary wound field structure disposed between the armature'and the main field structure with poles or pole faces magnetically in series with the main poles but separated therefrom by high reluctance gaps or members, the auxiliary poles or pole faces being magnetically bridged by members which readily saturate extending from pole to pole around the machine. In the forms shown, the auxiliary poles 4 are bridged by shunts 3, have insets of cobalt steel 11 and are separated from the main poles 1 by air gaps 7 or by non-magnetic material. In Fig. 5, the auxiliary pole has a main shunt winding 22 assisted by a shunt winding 26 in series with a resistance 27 and opposed by a winding 25 in series with the separately excited winding 8 on the main pole 1. In Fig. 4 the machine is a sub exciter 19 feeding the winding 18 of an exciter 16 of a main machine 14 across which is shunted a winding 8c on the main pole of machine 19, the main pole also having shunt and series coils 8a, 8d respectively also a coil 8 across a resistance 22 in the load circuit of the machine 14 while the auxiliary field member has shunt coils 10 which might alternatively be separatedly excited or connected in series with the coil 8a. The coils 8, 8a and 8d assist one another and are assisted or opposed by coil 8c. In the case of a Ward- Leonard equipment, the exciter or sub-exciter may increase the motor excitation and decrease that of the generator when the load current increases. The coils on the auxiliary system, which may be on the poles 4 or bridges 3 or on both may be reversed, open or short-circuited at will and when separately excited may be in series with a rectifier to ensure uni-directional excitation. The resistance 27 in series with winding 26 has a non-linear voltage-resistance characteristic.