DC filter capacitor is affected by the harmonic voltage and current in the operation and the noise problem is also existed. At present

related study on the noise of AC filter capacitor in China is made and

however

the study on that of DC filter capacitor is not sufficient. The noise frequency of AC filter capacitor is composed of the difference frequency

sum frequency and frequency doubling at AC voltage of various frequencies But in the DC filter capacitor

in addition to above three items

the vibration and noise of the frequency of the harmonic voltage itself is existed. In this paper

the influence of different loading condition the capacitor noise is analyzed through the noise analysis of DC filter capacitor. It is shown by the test result that the noise magnitude of mainly influenced by the DC voltage and the noise frequency is determined by the AC harmonic voltage and the sound power level of DC filter capacitor is proportional with logarithm of DC voltage.