A General Method to Measure Parasitic Capacitance of Transformer Using Guarding Technique

Precise, simple, and general measurement methods are essential for parasitic capacitance of transformer. Conventional two-terminal method has some limitations on the measurement of multi-winding transformer, like complex measurement processes. This paper introduces guarding technique into a new method to measure parasitic capacitance of multi-winding transformer. The principle and measurement processes of proposed three-terminal guarding method are introduced in detail. Comprehensive comparisons between two-terminal method and guarding method are made based on circuit verification and three case studies. Guarding method has high accuracy, but simpler measurement processes, and higher feasibility for multi-winding transformer compared to the conventional two-terminal method.