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  #1  
Old 04-06-2010, 07:37 AM
justin77 justin77 is offline
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Default Connect two transformers parallel

Can i connect two transformers after the AC to DC conversion in parallel as shown in the diagram.
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Old 04-06-2010, 08:36 AM
t_n_k t_n_k is offline
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You can - in this situation the highest output at any instant will conduct into the parallel load path - by virtue of the diodes D1 & D2.
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Old 04-06-2010, 09:12 AM
justin77 justin77 is offline
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Will the load get balanced. Will i be able to get more Amps from the combined circuit?
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Old 04-06-2010, 10:01 AM
t_n_k t_n_k is offline
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You could probably lose the diodes (D1 & D2). The bridge rectifiers will themselves prevent backflow of current.

Perhaps you could explain why you want to take this approach - is it for a real circuit?
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Old 04-06-2010, 03:14 PM
justin77 justin77 is offline
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Yeah this is. I need it to give power to my amplifier. One transformer is not enough as its maximum current is 2A. I need to have some method to provide 4A of current. So i was thinking of buying another 24 0 -24 V transfornmer and connet it in parallel.
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Old 04-06-2010, 03:29 PM
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nomurphy nomurphy is offline
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Instead of building two seperate circuits, literally place the two equally rated xfmr's in parallel to double the output current capacity. Verify the diode bridge can handle the extra current, or upgrade it.
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Old 04-06-2010, 03:40 PM
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SgtWookie SgtWookie is offline
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Make certain that you have the transformers connect in phase with each other.

If you have them out of phase, you will get 0v out and a pair of smoking transformers.

Connect the primaries to a fused and switched supply of mains power. Connect one of the ends of the secondaries together. Use a meter set to AC to test the voltage between the disconnected ends of the secondaries. If you have them in phase, you should measure very little voltage between the two. If they are out of phase, you will measure around 48vac.

If they are out of phase, you can swap either the primary or secondary connections.
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Old 04-06-2010, 03:54 PM
justin77 justin77 is offline
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Quote:
Originally Posted by nomurphy View Post
Instead of building two seperate circuits, literally place the two equally rated xfmr's in parallel to double the output current capacity. Verify the diode bridge can handle the extra current, or upgrade it.
Do you mean to connect the AC output's of the two tranformers in parallel?

Isn't it a risky thing to do. Isn't connecting DC outputs in parallel safer?
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Old 04-07-2010, 12:38 AM
Bychon Bychon is offline
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If the 2 transformers are same brand, same number, they will be perfectly happy in parallel. If they are a bit different, the use of 2 rectifier circuits (like the drawing shows) will keep them from fighting each other.

In the real world, I have connected transformers of different brands, but both labeled 24 VAC, and they do not fight each other, so a little bit of difference doesn't seem to hurt.
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Old 04-07-2010, 02:32 AM
justin77 justin77 is offline
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what if one DC output is 33.3V and the other is 35V only the 35V output generating transformer will be active.

Now if i draw 2A , 35V will drop to say 30V then the 33V transformer will become active. So only one transformer is ideally active at any one instance?

Am i corect?
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