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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: You sure about that?... posted by Steve O on January 9, 2017 at 20:28:44:
This is pretty basic stuff. To establish the rated full load current of the windings of a two winding single phase transformer, take the VA rating of the transformer and divide it by the rated winding voltage.
For example, for a 50VA transformer with a 120V primary and a 6.3 volt secondary, the rated full load currents are: Primary, 50/120 = 0.42A, Secondary, 50/6.3 = 7.9A.
So, if you wanted to make a buck transformer out of this by connecting the secondary in series with the primary in subtractive polarity (120-6.3 vs 120+6.3) and you needed it to be capable of supplying 3 amps to your load then the transformer would need to be rated 360VA minimum (120V x 3A) to have a primary winding capable of 3 amps.
To verify, I took a 135VA transformer, 120V pri, 6.3V sec. With my line voltage I got 128V additive polarity & 114V subtractive. Wired in subtractive polarity I connected a 60W light bulb and measured 474mA in the wire to the bulb. In the incoming wire to the transformer primary from the wall outlet I measured 480mA - a little higher as expected because of the transformer magnetizing current.
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Follow Ups
- RE: You sure about that?... - sayntjack 12:57:56 01/10/17 (6)
- Ah-Ha - Steve O 16:48:35 01/10/17 (5)
- RE: Ah-Ha - sayntjack 17:50:49 01/10/17 (4)
- Diagram posted (nt) - Steve O 18:16:08 01/10/17 (3)
- RE: Diagram posted (nt) - sayntjack 10:03:03 01/11/17 (2)
- RE: Diagram posted (nt) - sayntjack 10:10:34 01/11/17 (1)
- Okey doke (nt) - Steve O 15:20:53 01/11/17 (0)
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