A hunting analysis of a permanent-magnet alternator and a synchronous motor

Little has hitherto been written about the transient analysis of interconnected salient-pole synchronous machines of comparable size, where infinite busbars cannot be assumed to exist. The paper describes theoretical and practical work carried out on a simple power system of this type, in which a 60 kW permanent-magnet alternator supplies power to a synchronous motor. For analytical purposes the permanent-magnet alternator is shown to be equivalent to a conventional alternator with a constant field voltage. The measurement of the parameters of the machines is described and the steady-state performance of the interconnected system is predicted by Kron´s method of analysis. The hunting equations of the system are examined, and a frequencyresponse method involving Nyquist´s stability criterion is used to predetermine the effects of armature resistance on the hunting stability of the system under various conditions of load and saturation. A digital computer is used to perform the calculations and the predicted results are found to agree well with those obtained experimentally from the actual system.