Analysis and Actual Measurement of Coil-to-Coil Capacitance of High-Frequency Isolation Transformers for Suppression of High-Frequency Patient Leakage Currents

Placing the Transformer inside an Aluminum Case

Abstract

High-frequency isolation transformers are used to suppress high-frequency patient leakage current flowing in the insulated parts of medical devices. In this study, we assumed that the high-frequency isolation transformer would be placed in an aluminum case for actual case and researched whether the coil-to-coil capacitance was small enough to suppress the high-frequency patient leakage current below the regulated value. The coil-to-coil capacitance was analyzed and measured by changing the items laid in the isolation transformer, the presence of PTFE wrapped around the isolation transformer, and the number of ferrite cores used in the isolation transformer. The results of the analysis in the electromagnetic field simulation showed that the smallest capacitance was 5.040pF when two ferrite cores were used, PTFE tape was wound, and a 1.0mm PTFE plate was laid. The actual measurement also showed a minimum of 3.9807 pF in this case.