In recent years

the issue of capacitor noise problems has become more and outstanding and the noise mainly focuses on both bottom and top of the case. The study of influence degree of harmonic on the noise at bottom and top of case of single unit of capacitor has important significance to the noise suppression of complete capacitor device. In this paper

the reasonable limit condition is set in accordance with the generation mechanism of capacitor noise and four function relations among harmonic voltage amplitude

harmonic voltage frequency

harmonic current amplitude

harmonic current frequency and noise pressure level A are deduced based on the definition of each variables. Thus obtaining the influence of harmonic variation on the noise pressure level

namely the noise pressure level is increased gradually with the increase of harmonic amplitude and is linearly related to harmonic amplitude taking common logarithm;Within a definite frequency range and with the increase of frequency

the noise pressure level increases firstly and decreases subsequently

and the harmonic frequency corresponded by its maximum value is related to the value of time parameter. The correctness of the analysis method in this paper is verified through comparison to the related test result. According to the conclusion in this paper

the influence of harmonic on the noise can be defined conveniently

and the influence of such four factors as harmonic voltage

harmonic current

harmonic amplitude and frequency and their value on the noise of capacitor can be obtained.