Influence of the Winding Geometry and its Materials on the Resonance Behavior of Transformer Coils

Voltage stress due to steep impulses during switching operations of e.g. vacuum circuit breakers and ongoing harmonics caused by converters are a well-known but still increasing problem in the field of transformer design and operation [1]. In order to investigate the behavior of transformers during such impulses and oscillations, several models have been developed [2,3]. However, with increasing complexity of the coils, all studies show minor to major deviations in computation, compared to the corresponding measurements. Due to a high number of turns in the high voltage coils of transformers, the errors caused by simplifications or inaccurate data of the interwinding geometry can be tremendous. Hence, it is necessary to know which parameters are influencing the resonance behavior significantly and need to be represented accurately, while other parameters may be neglected. Therefore, a parameter study has been carried out, in order to analyze the resonance behavior of a simple coil geometry, based on FEM computations.