Phase advancers of the Scherbius type

The Scherbius phase advancer has recently been adopted as a permanent addition to certain types of 3-phase motor. The author gives a simple theory of the advancer, and applies the equations to an analysis of an ¿All-Watt¿ motor. It is shown that quantities usually regarded as constants are not constant in actual practice. In this connection the effect of brush resistance and saturation of the advancer iron are dealt with. When these variations are taken into consideration the agreement between prediction and test is very close, but the locus diagram of primary current is no longer the arc of a circle, although it can be arrived at from a series of such arcs.