Self-excitation of induction motors

It has been known for some time that an induction machine whose rotor is driven mechanically may become self-excited if capacitors are connected across its terminals. The present paper is concerned with the predetermination of the machine characteristics when operating under such conditions. The frequency of excitation is very close to the synchronous frequency corresponding to the speed of the rotor. The voltage to which the machine will excite is dependent upon its no-load excitation characteristics at that frequency, the criterion to be satisfied being that the lagging volt-amperes of excitation equal the leading volt-amperes of the capacitors.