A high-frequency semi co-axial transformer with high insulation voltage

A semi co-axial transformer concept is described which can be used to transfer energy across a relatively high potential difference without using potting components. The intended purpose of the design is to provide electrically insulated power for heating up the semiconductor devices in a double-pulse test circuit operating at several kilovolts. Because of the requirement of handling the large potential difference, a large leakage inductance is anticipated and the LLC topology is used to solve the issue of excessive voltage drop. The transformer is implemented using ring cores and a primary winding which is led through the center inside a shielding tube which in turn has several millimetres of insulation on the outside. Apart from the aspects of insulation, this work deals with the choice of core material, wire thickness and type, determining the transformer properties, including the magnetic and electrical losses. Distinctive features in the design are the configuration which approaches some of the properties of a coaxial configuration and the inclusion of a thick metallic shield. Results show that a good prediction of the performance can be achieved using relatively simple techniques.