Exciter instability: Part I — Discussion of the problem

A. Introductory INSTABILITY of an exciter has come to have a number of meanings: (1) large change in voltage for a small change in load; (2) creeping of voltage, up or down, without apparent cause; (3) temporary removal, partial or total, or even reversal of the excitation accompanying sudden short circuit of the alternator; (4) slow oscillation, or possibly reversal, of excitation following a sudden readjustment of either the shunt field or alternator field rheostat;¹ (5) “grabbing” the load, etc. when in parallel with other exciters. The last mentioned trouble, which is experienced largely, although not altogether, on compound-wound machines does not occur if respect is given to well-known characteristics of direct-current machines as discussed in any text book on the subject. Therefore this paper deals only with the first four phenomena mentioned above.