Filter capacitors have become the main audible noise sources in high voltage direct current converter stations. Large numbers of filter capacitor units are mounted on racks with a great height

and radiating audible noise into surroundings.In order to settle the audible noise problem of filter capacitors

the generation mechanism of capacitors vibration needs investigating firstly. In this paper

the electric forces in power capacitors were analyzed based on its structure.The electric force was proportional to the squared of voltage applied on capacitors. Furthermore

vibration of capacitor’s internal packet was measured.The results show that capacitor packet had several discrete natural frequencies. When electric force frequency was equal or close to any one of these natural frequencies

capacitor packet was in resonant status and has increased vibration amplitude.Besides

vibration shape on capacitor surfaces was measured in order to study vibration-transmission pathways.It was found that internal packet vibration firstly transferred to bottom and top surfaces of a capacitor

and then travelled through edges onto lateral surfaces.