Development of magnetic dynamic damper for nuclear power plant

This paper describes a magnetic dynamic damper (MDD), which is a passive vibration absorber employing a permanent magnet and a conductor for both the restoring and damping force. The basic characteristics of this magnetic spring and damper system are examined through static loading tests and vibration tests using a pair of double cylindrical magnets. It is confirmed that the magnetic force analysis accurately simulates these test results. Application of this system to a rotating machinery model shows that the MDD can effectively reduce two-dimensional vibration. Moreover, through the forced vibration test in which MDD is attached to the bottom of vertical pump, it is examined that the proposed MDD can be applicable for seismic response reduction over the wide region of pump casing displacement. The top heavy valve equipped on piping vibrates biaxially at different frequencies. In this case, it is confirmed from the vibration tests using a valve-piping model that the MDD with multiple rectangular magnets is effective in reducing two-dimensional vibration with different frequencies. (author)