In HVDC systems

the vibraiton and audible noise of filter capacitors have frequency spectra

which are generally grouped by adding

subtracting and doubling between each harmonic currents frequencies. However

some filter power capacitors possess different frequency characteristics. Thus

we investigated these phenomena in order to consummate the mechanism of capacitor vibraiton and noise. Experimental results show that there are two types of frequency characteristics of noise generated by capacitors loading single frequency harmonic current: 1) noise frequency spectra are integer multiple of harmonic current; 2) noise frequency spectra are even-numbered multiple of harmonic current

which is called multi-times-frequency spectrum phenomenon.To analyze its mechanism

a dynamic equation of two-plate capacitor is established based on the Lagrange Mechanics. By solving the equation

the vibration of electrodes is consistent with vibration frequency of power capacitor in experiments. It is concluded that the coupling of vibration and electric field will lead to multi-times-frequency spectrum phenomenon. When the frequency or its double of harmonic current is closed to natural frequency of power capacitor

the multi-times-frequency spectrum phenomenon will be more notable.