The analysis of hunting by means of vector diagrams

With the increasing use of automatic control of electrical machines, and the high accuracy often required in such systems, stability problems have become increasingly important. The paper describes the analysis of some tests which have been carried out on electrical equipments in which hunting occurred. The hunting is considered as a condition of self-excitation, setting up alternating voltages and currents which are independent of the normal operation of the equipment, and are superimposed on the useful voltages and current. The way in which the hunting is sustained by self-excitation is analysed by means of vector diagrams, which give a picture of the behaviour of the circuits, and enable the factors causing hunting to be studied.