Vibration reduction of electric equipment using an electromagnetic dynamic vibration absorber: Shaking table tests and numerical simulations

This study proposes an electromagnetic dynamic vibration absorber (EMDVA) to reduce the seismic vibration of equipment in nuclear power plants. Its effectiveness is validated through shaking table tests of the integrated equipment-EMDVA system, with excitations generated by a thorium molten salt reactor (TMSR) model, considering the interaction with soil and plant structures. The EMDVA, integrating linear springs and electromagnetic spring elements with nonlinear stiffness, achieving a wide control frequency range while reducing sensitivity to variations in excitation amplitude. The damping mechanism is analyzed through theoretical and experimental studies of electromagnetic springs. Results reveal that the EMDVA transfers vibration energy to a wider frequency range and dissipates it quickly, outperforming the linear DVA in electrical cabinets. Increasing nonlinear stiffness broadens the control bandwidth but reduces stability to excitation amplitude variations. Parameter analysis shows that when the initial nonlinear stiffness proportion is 50–80 %, the EMDVA offers a significantly wider control bandwidth with minimal sensitivity increase. Under intense excitations, the EMDVA can decrease the maximum working stroke compared to the DVA, making it more suitable for space-constrained equipment applications.