Calculating Transformer Inrush multiplier from Open Circuit tests Results
Calculating Transformer Inrush multiplier from Open Circuit tests Results
(OP)
Hi,
I am trying to understand how you can calculate a transformers inrush multiplier from its open circuit test data. The transformer in question are 2.2MVA, 33/0.44kV, Dyn11, z= 6% (IEC design)
I have seen a few test reports, and also EMTP-ATP where they seem to have taken the transformer test results and seem to get the transformer inrush current, but i cannot quite see how this relationship works. I presume it is some sort of extrapolation from obtaining the magnetizing reactance (I0) - but i cant quite see how to pull all the information together, and a read through my textbooks and the web hasn't shed any light so far... so i am hoping someone with a better understanding of transformer theory can help!
FYI - i have been told by the manufacturer the inrush multiplier is 5x,and i know they calculate this using some complex formulas (Holcomb, Sprecht, Bertagnolli, etc..) but i think they can prove this by test - which is what i am trying to figure out.
Ta
Steve
I am trying to understand how you can calculate a transformers inrush multiplier from its open circuit test data. The transformer in question are 2.2MVA, 33/0.44kV, Dyn11, z= 6% (IEC design)
I have seen a few test reports, and also EMTP-ATP where they seem to have taken the transformer test results and seem to get the transformer inrush current, but i cannot quite see how this relationship works. I presume it is some sort of extrapolation from obtaining the magnetizing reactance (I0) - but i cant quite see how to pull all the information together, and a read through my textbooks and the web hasn't shed any light so far... so i am hoping someone with a better understanding of transformer theory can help!
FYI - i have been told by the manufacturer the inrush multiplier is 5x,and i know they calculate this using some complex formulas (Holcomb, Sprecht, Bertagnolli, etc..) but i think they can prove this by test - which is what i am trying to figure out.
Ta
Steve






RE: Calculating Transformer Inrush multiplier from Open Circuit tests Results
RE: Calculating Transformer Inrush multiplier from Open Circuit tests Results
RE: Calculating Transformer Inrush multiplier from Open Circuit tests Results
Open Circuit tests -> Transformer equivalent circuit -> Use this to calculate the flux vs current characteristic curve -> From flux-current curve you can get the peak value and get your inrush multiplier
I can't quite draw all the strands together though as I can't quite remember my electromagnetic theory. I am sure this is how the BCTRAN model in EMTP-ATP works, but i can't find enough detail on the model to figure it out.
FYI the 5x multiplier is unusually low, but i believe theses particular transformers are deigned this way as they are frequently connected to a weak distribution system and can cause problems with excessive voltage dip if the inrush is too high.
RE: Calculating Transformer Inrush multiplier from Open Circuit tests Results
RE: Calculating Transformer Inrush multiplier from Open Circuit tests Results
RE: Calculating Transformer Inrush multiplier from Open Circuit tests Results