Dynamo. Compound

A compound wound dynamo; one which has two coils on its field magnet; one winding is in series with the external circuit and armature; the other winding is in parallel with the armature winding, or else with the armature winding and field winding, both in series. (See Winding, Long Shunt--Winding, Short Shunt.) Such a dynamo is, to a certain extent, self-regulating, the two coils counteracting each other, and bringing about a more regular action for varying currents than that of the ordinary shunt or series dynamo. The extent of the regulation of such a machine depends on the proportions given its different parts. However good the self-regulating may be in a compound wound machine, it can only be perfect at one particular speed. To illustrate the principle on which the approximate regulation is obtained the characteristic curve diagram may be consulted. IMG:8956969607833025625_196F137.jpg: Fig. 137. CURVES OF SERIES AND SHUNT WINDINGS SUPERIMPOSED. One curve is the curve of a series winding, the other that of a shunt winding, and shows the variation of voltage in each with resistance in the external or working circuit. The variation is opposite in each case. It is evident that the two windings could be so proportioned on a compound machine that the resultant of the two curves would be a straight line. This regulation would then be perfect and automatic, but only for the one speed. 197  STANDARD ELECTRICAL DICTIONARY.