Vibration Protection for Rotating Machinery

Vibration protection becomes desirable for rotating machinery when it is operated with certain defects. Electric generators may be operated with a single ``ground´´ on the rotating field circuit without harm but the potential hazards of a second ``ground´´ at another point on the same circuit are so great that the need of protective equipment for automatic disconnection of the generator is evident. Double ``grounds´´ on a rotating field circuit may short-circuit a large part of the winding, unbalance the magnetic field, and set up vibrations of such serious magnitudes that the machine may be wrecked. A method for obtaining satisfactory vibration protection for rotating machines has been developed. It uses equipment most of which is already on hand or readily available to most companies operating important machinery. The only part requiring construction is an electronic amplifier. The equipment, its operating characteristics, wiring, and performance are described in this paper. The described protective equipment has been in service on one machine since the latter part of 1942. It has given entirely satisfactory service. Another machine was protected in a similar manner for about three months until it was found convenient to rewind the field.