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Parallel secondary windings
Parallel secondary windings
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Old 25th March 2004, 01:00 PM   #1
jlm is offline jlm  France
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Default Parallel secondary windings


Is it possible to connect in parallel secondary windings of several identical transformers? For example 4 toroids ( 2 x 25 V - 10 A - 500VA ).

Config 1 with 4 bridges and config 2 with 1 bridge

If yes, which of these 2 configurations is preferable and which of these 2 configurations will permit me to have the equivalent of a transformer of 25 V - 80 A - 2000 VA?

Thanks and Regards
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Old 25th March 2004, 10:36 PM   #2
GRollins is offline GRollins  United States
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Yes, you can parallel identical transformer windings. Many transformers these days come with two ratings--one with the secondaries in series and another with them in parallel. It makes no difference if the windings are on different transformers.
I'm not sure that I follow what you mean about rectifiers.

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Old 25th March 2004, 10:47 PM   #3
sreten is offline sreten  United Kingdom
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The 4 bridge option is safer and will have lower
rectifier losses than the single bridge version.

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Old 25th March 2004, 11:03 PM   #4
xenofex is offline xenofex
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I did parallel 2 identical transformers with 4 bridge for my A5

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Old 25th March 2004, 11:11 PM   #5
Christer is offline Christer  Sweden
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If we are talking simply tying the secondaries together in
parallel, then there seems to be different opinions judging
from previoous threads on this topic.

Datasheets for Transformers with low VA ratings often say that
it is OK to parallel the secondaries of a single transformer at least.
Probably the winding resistance is highe enough to smoothe
out slight variations in voltage, or the manufacturing precision
assures an identical number of turns for the windings. For higher
rated transformer, i suppose a slight mismatch would have
larger consequences and it may, perhaps, be wise to have a
small resistor in series with each secondary before tying them
together, which anyway can have some advantages to smooth
out the cap charging pulses.
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Old 26th March 2004, 01:23 AM   #6
labjr is offline labjr  United States
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I imagine you need to have the phase correct. Other than that I don't think it would be a problem.

I think it would be more expensive to use multiple transformers, unless you can get them cheap or surplus.
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Old 27th March 2004, 11:39 AM   #7
Brian Donaldson is offline Brian Donaldson  United States
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I would use a seperate bridge for each transformer so they don't fight each other when the load is light. Dead shorting different windings on a single transformer is OK, but there may be some small difference between sperate transformers. But if the feed different bridges and one puts out less voltage, it can freewheel until the supply sags a bit an it then contributes. Make sure you have matching bridges (same forward voltage drop).

Since you posted in Pass Labs area, I'm assuming this is for a class A amp. Then you should have each transformer feed its own bridge, first bank of capsand an inductor or resistor then connect together to the last common set of caps.
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