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tyipcal X/R ratio for an autotransformer

tyipcal X/R ratio for an autotransformer

tyipcal X/R ratio for an autotransformer

(OP)
finding typical X/R ratios for standard transformers is pretty easy to find, however, I cannot find any information on a typical autotransformer X/R ratio. Only data I can find is from a Siemens PSSE model report on a project with an autotransformer that claims the impedance (per unit) is 0 + j0.092). Does this data make sense? (no resistance, only reactance, and thus X/R is N/A?)

RE: tyipcal X/R ratio for an autotransformer

In my models, I am seeing a range of 58 to 85 for the X/R on autotransformers. That is high enough that the small amount of resistance the transformer has will play no role in short circuit or power flow calculations. Its impedance is almost entirely reactive.

RE: tyipcal X/R ratio for an autotransformer

(OP)
Thanks!! I looked everywhere for this info; Star for your help!!

RE: tyipcal X/R ratio for an autotransformer

The transformer test report provides enough information to calculate both the R and the X.

RE: tyipcal X/R ratio for an autotransformer

If you know the transformer losses, you can calculate the resistance, since any real power losses will appear as a resistive circuit element. Knowing the %Z and the R, you can calculate the X/R.

RE: tyipcal X/R ratio for an autotransformer

What is the rating ( % impedance, voltage and MVA ) of the auto-transformer that you are modelling ?

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