Disturbances in the Behaviour of Alternating - Current Machines by Self-Excited Electromagnetic Phenomena

During the last few years many vibrational problems have been encountered on synchronous and asynchronous machines. The torsional vibrations of a.c. generating sets on ships were so large that a vibrationless parallel operation became impossible. With asynchronous machines, lateral vibrations of the rotor disturbed the operation in such a way that the rotor soon touched the stator inner surface. In both cases the problem was caused by electromagnetic self-excited phenomena, in connection with the mechanical damping of the rotor.