Rise time reduction in high-voltage pulse transformers using auxiliary windings

Today high-voltage pulses are reaching more fields of application. High-voltage pulse transformers are often used in association with high-voltage pulse generating circuits to further increase the pulse output voltage level. However, because of the transformer parasitic elements involved, the transformer is the critical device in shaping the rising characteristics of the output pulse. One of the techniques usually adopted to decrease the leakage inductance of the transformer adds two auxiliary windings to the transformer. If properly used, these auxiliary windings reduce the leakage flux and, therefore, the leakage inductance. As a result the pulse rise time is reduced. In this paper, a mathematical model is used to describe the observed behavior of a transformer operating with auxiliary windings, based on the theory of electromagnetic coupled circuits. The model is discussed regarding the experimental results obtained from a high-voltage test transformer associated with a high-voltage pulse generating circuit, and the simulation results obtained from the numerical evaluation of the developed differential equations implemented in Matlab/Simulink with the measured transformer parameters.