Richard F. Guardiani

Vibration cancellation apparatus with line frequency components

Vibration induced by electromagnetic forces at an AC power line frequency are cancelled using inertial masses that are oscillated at the line frequency, out of phase with the vibration induced by the electric power due to operation of a machine. The machine can be a rotating device such as a nuclear reactor coolant pump, that is vibrated at component frequencies and harmonics related to the rotational speed and line frequency as well as sum and difference frequencies due to beating of these frequencies together. Cancellation components at the line frequency and it harmonics minimize the generation of annoying sideband acoustic components, which also may contribute to hearing damage. The line frequency cancellation devices preferably include four inertial mass shakers mounted on the outside of the housing of the pump, at 90° intervals, each mass being displaceable in an oscillating manner along three perpendicular axes, for cancelling axial, lateral and torsional vibration coupled to the housing from the rotor. This mounting requires no penetration of the pressure barrier defined by the pump and plates the shaker mechanisms out of contact with heat, pressure and fluid conditions in the pump.