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Old 20th October 2005, 10:13 PM   #1
Klimon is offline Klimon  Belgium
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Default Wiring secondaries of two power trafo's in parallel?


Am I right to think that parallelling the secondary ht windings of two identical power transformers (primaries also parallelled with respect to phase) will result in: same voltage as one trafo; current rating doubles; internal resistance is half of one trafo?

Are there any electrical drawbacks to this approach?

I could also go dual mono but the parallelled approach (if my suppositions are true that is) fits better for the amp I'm planning + needs less filter components...

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Old 20th October 2005, 10:23 PM   #2
Tweeker is offline Tweeker  United States
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If they arent perfectly matched, they wont share current perfectly. Low value output resistors might possibly be called for.
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Old 20th October 2005, 10:43 PM   #3
Klimon is offline Klimon  Belgium
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Okay - thanks!

I have four identical trafo's so will pick two with matching primary & secondary winding resistance.

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Old 20th October 2005, 11:09 PM   #4
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Still not guaranteed. If one transformer outputs 40V, the other 39.9 V, and the secondary resistance is 0.2 ohms, then you have 0.5 amps flowing from the higher voltage one to the lower. Also the output voltage can change under load because primary and core losses might be different for the two as well, so you're really looking at a suboptimal situation.

I'd recommend dual mono. You'll feel virtuous doing it, too.

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Old 21st October 2005, 12:22 AM   #5
Klimon is offline Klimon  Belgium
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Back to dual mono than! And this time right ... my previous amps were meant to be dual mono but I accidently parallelled power trafo's on both occasions... strangely enough one plays perfectly while the other one almost burned both it's trafo's - ...... I did experience the virtuous-feeling thing however
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Old 21st October 2005, 01:22 AM   #6
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You could parallel the primarys, then series the secondarys 4 ohm taps, then you'll have pretty good sharing, but they won't fight each other.
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