# Design Step Down AC Transformer from Scratch

Discussion in 'The Projects Forum' started by Mouses, Mar 1, 2015.

1. ### Mouses Thread Starter New Member

Mar 1, 2015
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Hi,

I want to design transformer to step down from 120 V @ 60 Hz on primary to 15 V and max 1 A of current on secondary . To make winding easy for me I am going with EI core.
I hope to utilize Kgfe (core geometrical constant) method how to determine core size but even if I had spent countless hours looking into datasheets of different manufacturers (I don't want to break any anti-advertisement rule here, but one of them is mentioned in linked pdf about Kgfe method in the beginning of example #1. ), I wasn't able to convert provided specs into Kfe (core loss coefficient) and Beta coefficient.
Given that core loss Pfe = Kfe*(dB^{Beta})*Ac*lm
Can you point me out as how to use this method with data which are actually available?

Thanks.

2. ### ronv AAC Fanatic!

Nov 12, 2008
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Bernard likes this.

Jul 18, 2013
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It has been my experience so far that there is virtually no definitive transformer design criteria out there.
Max.

Mouses likes this.

Sep 30, 2009
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5. ### Dodgydave AAC Fanatic!

Jun 22, 2012
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Thats a 8:1 turns ratio, just select the size of wire that will give you the secondary current.

6. ### Mouses Thread Starter New Member

Mar 1, 2015
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Thanks,
although it doesn't seem to be related to Kgfe method. I will go through it and post back if I am able to put it in any relation with the theory I am already familiar to.
M
I'll check - thanks.

7. ### Mouses Thread Starter New Member

Mar 1, 2015
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Thanks, but I wanted to compute size of the core with that particular method which I've mentioned. I don't have troubles with turn ratio.

8. ### Mouses Thread Starter New Member

Mar 1, 2015
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Yes, I have already been on that site.