Analysis and estimate of the influence of the leakage inductance of the charging transformer primary on the amplitude stability of the PFN charging voltage

The technology of the pulse-forming network (PFN) being resonantly charged with the PFN charging voltage being stabilized by the deQing circuit has been widely used for developing the line-type modulator over the last several decades. Experience shows that the leakage inductance of the charging transformer primary needs to be less than 2% if the required output pulse amplitude stability of the modulator is about 0.1%. This paper studies how the leakage inductance influences the amplitude stability of the PFN charging voltage in the case of using the deQing circuit, explains the mechanism, presents an estimate method, develops the formulae, and reveals the laws. These formulae are not only useful in modulator design for properly specifying the leakage inductance and the related specifications, but also in showing how to improve the amplitude stability of the PFN charging voltage.