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Transformer Impedance-Inrush

Transformer Impedance-Inrush

Transformer Impedance-Inrush

(OP)
Its a liquid filed 3000KVA/4000KVA, 13.8/600 delta wye, z=10%. Is inrush current still 12 time the FLA for .1 sec?

RE: Transformer Impedance-Inrush

Per IEEE, yes.

RE: Transformer Impedance-Inrush

It is 12X for a zero impednace source but will be reduced as the source Z increases.
JIM

RE: Transformer Impedance-Inrush

Hi Humble2000 (Electrical)
According to Siemens "Formel und Tabellenbuch" the inrush current depends upon Rated Power .So for 3000/4000 KVA would be 6 [from 13.8 kV] and 10 supplied from 0.6 kV. The inrush current amplitude would be half of the above value for at least 10 up to 60 cycles. For 60 Hz [one cycle=1/60 second] from 1/6 up to 1 second. So for 0.1 seconds would be sure above the half.
Best Regards

RE: Transformer Impedance-Inrush

(OP)
7anoter4
what is siemens "Formel und Tabellenbuch" ?
Thanks for the responce though. I am also woriied about cold and hot load pick up. cold load pick up could be 15 times more right? any information on these values?

RE: Transformer Impedance-Inrush

The 12x figure is a very rough approximation used to determine boundary for primary protection.  

Source impedance does have an effect, as you suggest.  There was some discussion here several months ago regarding a white paper by S&C that discussed this issue.  You might search this forum or see if you can find it on S&C webpages.

RE: Transformer Impedance-Inrush

Re: "I am also worried about cold and hot load pick up. cold load pick up could be 15 times more right? any information on these values?"
These items are different from the magnetizing inrush in both magntiude and duration. You need to differentiate if the load is a utility feeder residential, industrial load etc all of which may have much different characteristics.
JIM
 

RE: Transformer Impedance-Inrush

(OP)
Well, thats hard to calculate precisely, I beleive. Any litreture on this subject?

RE: Transformer Impedance-Inrush

Hi Humble2000
Siemens AG is well known Manufactory company for Electrical Product including High Voltage Equipment  and Transformer.
The actual table [Translated] is as follows:
Siemens AG Berlin Muenchen
Formel- und Tabellenbuch für Starkstrom-Ingenieure [Formula and table book for power engineers] 1965[see attachment]

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