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Transformer inrush current - 2

Transformer inrush current - 2

Transformer inrush current - 2

(OP)
Once more on the same topic..I could locate some literature for calculating the worst 1st cycle inrush, based on the Transformer parameters like flux density, dimensions etc.See attached.

Next, I tried my hand at calculating the reduction in inrush because of line reactance. The reduction was not as much as desired. 1540Amps reduced to 1340Amps approx for a 150kVA, 3Ph, Dy Transformer. The power supply cable was 4/0, 200m. Does anybody have any idea on the transient analysis program for carrying out a study?

It is my belief that accounting for source impedance & cable resistance will further lower the inrush value.

RE: Transformer inrush current - 2

Quote:

It is my belief that accounting for source impedance & cable resistance will further lower the inrush value.

Is someone disagreeing with you on this?  The S&C white paper referenced in previous thread (I think) confirms this.  The cable impedance effectively increases the source impedance.  

 

RE: Transformer inrush current - 2

(OP)
I am looking for a rigorous calculation to get the final value. Thanks for the support.

RE: Transformer inrush current - 2

There is no final value.  The inrush depends on voltage phase angle at energization as well as remanence flux.  You can estimate a maximum worst-case value, or get it from the transformer supplier.  

Perhaps a transient program such as ATP can help - it may have already been modeled at some point, but you'll need a lot of specific data on the particular transformer of interest.  And make quite a few assumptions.

http://www.emtp.org/

RE: Transformer inrush current - 2

cherry2000
For what you need a final value?
Take a worst case,as Dave recommended.
Best Regards.
Slava

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