Incorporating capacitance into partial-core transformer models to determine first natural resonant frequencies

Capacitive components are added to partial core transformer models to allow resonant analysis at harmonic frequencies (50-5 kHz). The harmonic frequency responses of partial core transformers with relatively low turns ratio are analysed with the model. Capacitive loads of various magnitudes are then connected to the secondary terminals in order to calculate loaded resonant frequencies. The calculated values are validated with test results. The harmonic frequency responses of two high-voltage partial-core transformers with large turns ratio are presented. Calculations of the transformers´ first natural resonant frequency were validated with test results. Additionally, a capacitive load was placed across each of the secondary terminals and the loaded resonant frequencies, calculated by the model, are compared to the measured values.