I possess a continuous disc-type transformer consisting of 40 discs. Utilizing the geometrical dimensions of the transformer, I computed the impedance parameters for a ladder model. However, upon plotting the Frequency Response Analysis (FRA) for the transformer using these obtained values, I observed that the peaks and troughs persist beyond 2 MHz and extend up to 15 MHz, which is not physically feasible. How can I ensure that all the peaks diminish before 2 MHz?
If you have measured SFRA results, then you can compare with the computed SFRA results. If they are matching, then you can ignore the portion beyond 2 MHZ, the limit specified by IEC. The measurement results will also give crests and troughs beyond MHz range. The only question is the physical relevance of such measurements to understanding the transformer. If they are not matching, most likely, you have missed elements in the ladder network, for example, mutual inductance. The model has to be validated.
Frequency Response Analysis (FRA) is a valuable technique used to assess the mechanical integrity of power transformers. Let’s explore how you can reduce the frequency range of an FRA plot:
Understanding FRA and SFRA:FRA measures the ratio of a steady sinusoidal output to a steady sinusoidal input in a test object. Sweeping through the frequency range of interest gives rise to Sweep Frequency Response Analysis (SFRA).
Interpreting SFRA Results:
- SFRA traces reveal resonances (peaks and valleys) corresponding to combinations of capacitance and inductance within the transformer coils.
- Changes in resonance indicate mechanical alterations in the windings.
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