Theory of the Three-Wire D-C. Generator with Two-Phase Static Balancer With Special Reference to Magnetic Phenomena in the Balance Core

When a three-wire d-c. generator with a two-phase static balancer operates with an unbalanced load it is possible that cumulative saturation effects may exist in the balancer core whose magnitude is out of all proportion to the small magnetic unbalance which usually results from the design of the balancer phases. By obtaining an expression for the e.m.f. induced in the balancer winding by the alternating flux the conditions under which these phenomena may be present are studied. It is shown that they are affected by any difference in the resistance of the phases, and that in general their magnitudes vary inversely as the sum of the resistances of the armature winding and the balancer. These conclusions are confirmed by test results and oscillograms taken on an actual machine which show that the maximum flux density in the balancer core may rise to as much as twice the value for which it was designed. The large peaks which occur in the magnetizing current affect the heating of the balancer and also, to a less extent, that of the generator. They also cause considerable pulsations in the terminal voltages of the system.