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Old 15th December 2014, 10:49 PM   #1
August is offline August  Netherlands
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Default Transformer starting point: why toroid?

I've been reading here on the fora a lot. Recently the FirstWatt clones really interest me. I was just thinking materials now.

Why are toroid transformers used? Could other types be used? I can get a couple of big transformers with 26V secundaries from some UPS systems. Good starting point for a FirstWatt project? Thanks.
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Old 15th December 2014, 11:21 PM   #2
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Toroids can be smaller, EI plates are large, No real reason if designing from scratch. Oh yes, toroids have no air gap, so no good for output transformers.
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Old 16th December 2014, 12:22 AM   #3
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26V. Probably a good starting point for some kind of project. Centre tapped or single secondary? If single-sided, are they identical? When you say big, do you know how much current? If not, what do they weigh?
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Old 16th December 2014, 06:03 AM   #4
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Toroids can run at higher flux and have lower losses, partly as a result of this. Also they radiate lower stray flux. They do have a downside however - increased inter-winding capacitance.
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Old 16th December 2014, 01:18 PM   #5
August is offline August  Netherlands
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Quote:
Originally Posted by counter culture View Post
26V. Probably a good starting point for some kind of project. Centre tapped or single secondary? If single-sided, are they identical? When you say big, do you know how much current? If not, what do they weigh?
Single sided, identical, 6.5 kg = 14.3 lbs
Core measures 135 x 162 x 40mm = 5.3 x 6.3 x 1.6 inches. Should be good for some nice amps? True dual mono configuration.

Was thinking along the lines of a balanced F5(t) or F6.

Last edited by August; 16th December 2014 at 01:35 PM.
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Old 16th December 2014, 01:35 PM   #6
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Quote:
Originally Posted by August View Post
Why ?
Standard power transformer and cheaper.
(even 30-35 years ago, obtaining an EI/U/C in a >100VA size was difficult here, best chance was buying a core package abroad and WIY)

A potentially better transformer type is much more expensive, and even harder to get (strip wound core transformer, O-core, R-core, etc.)
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Old 16th December 2014, 01:45 PM   #7
August is offline August  Netherlands
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Well, the ones I can get are salvaged so also cheap (€20/each) and surely big enough for a nice project? Or better to get standard types specified? Thanks.
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Old 16th December 2014, 01:57 PM   #8
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I'm so cheap I don't even pay for sex.

If they do not hum(p), and you don't mind building larger amp cases, why spend money if you can be a cheapskate.
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Old 16th December 2014, 03:04 PM   #9
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I read somewhere that UPS transformers don't work so well in reverse. This in part may be due to them having an air gap to prevent saturation from the driving circuitry when being used as intended.
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Old 16th December 2014, 05:39 PM   #10
August is offline August  Netherlands
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That's could be a slight problem. Can anyone confirm this for the ups transformers?

Lol@jacco like the Belgians make Dutch jokes and the English make Scots jokes. Cheap is good and free is better, but I would pay for a good transformer. They should be as good as, if not better than stock toroid stuff.
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