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07-22-2013, 03:26 AM #17
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Sigurthr
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Re: Wiring transformers in parallel

It depends on how much ripple is too much for your application. For the life of me I cannot remember the formula for Vripple per Y capacitance at X current. I had it in a notebook some time last year but it is no where to be found now.

Edit; scratch that I just found it!!

Vripple = I / 2fC

I is current in amps
f is frequency of pulses
C is capacitance in Farads
Vripple is in volts (but I can't remember if it's Vrms or Vpk).

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Last edited by Sigurthr; 07-22-2013 at 03:28 AM. Reason: Found it!

07-23-2013, 07:10 AM #18
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Cyparagon
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Re: Wiring transformers in parallel

^Neither. It's Vpp

Quote:
 Originally Posted by Zeebit One more thing. I need to use both +/-12V rails instead of +12 and the tap.
If you want 24V, you want your transformers in series, not parallel. Or maybe I'm missing something because the topic changes every few posts.
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Last edited by Cyparagon; 07-23-2013 at 07:11 AM.

07-23-2013, 08:33 AM #19
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Zeebit
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Re: Wiring transformers in parallel

After the bridge rectifier I should get three outputs: +12V, GND and -12V. I have already made the power supply and Im using both +/-12V rails.

07-23-2013, 05:50 PM #20
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Cyparagon
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Re: Wiring transformers in parallel

I don't see how it's possible to get +/-12VDC from 12VAC and a bridge rectifier. Schematic?
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07-23-2013, 05:55 PM #21
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DashApple
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Re: Wiring transformers in parallel

Quote:
 Originally Posted by Cyparagon I don't see how it's possible to get +/-12VDC from 12VAC and a bridge rectifier. Schematic?
Kinda got lost from post to post but The transformer is a 12V centre taped , 12V - 0 - 12V , So 24V across the 2 windings which are in series .

Im combination with a rectifier will give the 12V+ , 12V- Rails .

Something like that anyway .
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Last edited by DashApple; 07-23-2013 at 06:01 PM.

07-23-2013, 11:42 PM #22
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Zeebit
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Re: Wiring transformers in parallel

Yep. Its a split rail power supply.

From wiki:
Quote:
 Volts center tapped (VCT) describes the voltage output of a center tapped transformer. For example: A 24 VCT transformer will measure 24 VAC across the outer two taps (winding as a whole), and 12 VAC from each outer tap to the center-tap (half winding). These two 12 VAC supplies are 180 degrees out of phase with each other, thus making it easy to derive positive and negative 12 volt DC power supplies from them.

07-24-2013, 12:29 AM #23
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djQUAN
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Re: Wiring transformers in parallel

It's also possible to do it with a single 12V winding using a voltage doubler. It'll have more ripple though.

07-24-2013, 03:35 AM #24
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Cyparagon
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Re: Wiring transformers in parallel

Then that's a 24V center-tapped transformer. NOT a 12V transformer.

A 12V center-tapped would be 6V and 6V.
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