Can I use a centre tapped 3 wire trafo to create a single rail output.?
I'm thinking 2 X AC to BR, CT to chassis ground.
And then the 2 DC outputs from the BR give me a single rail ...with a floating '0'?.
I'm thinking 2 X AC to BR, CT to chassis ground.
And then the 2 DC outputs from the BR give me a single rail ...with a floating '0'?.
You can either:
The parallel setup takes the voltage of both windings and puts them side by side. Doing this with one winding in reverse results in 0v, with both windings cancelling each other out. Your power rating is higher, at double the current rating of one coil.
Deciding which is best out of these will depend on your requirement of current, required voltage, available transformer voltages/current handling and/or voltage after your regulators (if used.)
To enlighten you on your proposal:
The reason it'd be a bad one is that this will most likely end up burning your BR diodes out, due to imbalanced current, if you use the split supply at all.
If you do not need the split supply / half voltages, put the windings in series and isolate the center tap. It effectively works as one coil of double the length now.
The image that @euro21 posted depicts parallel operation of the windings.
I hope this helps you somewhat!
- use the two windings in series, with the center tap taped off (if that's just one wire) or with the center taps twisted together (if it's two series windings).
- use the two windings in parallel, making sure that you either have a two-wire center tap, or create one (which is often possible by digging out the single wire, splitting the windings, and attaching a second wire.
The parallel setup takes the voltage of both windings and puts them side by side. Doing this with one winding in reverse results in 0v, with both windings cancelling each other out. Your power rating is higher, at double the current rating of one coil.
Deciding which is best out of these will depend on your requirement of current, required voltage, available transformer voltages/current handling and/or voltage after your regulators (if used.)
To enlighten you on your proposal:
This would create a single voltage only for items connected across the two terminals of the bridge rectifier's output. Connecting the center tap to chassis would still provide a midway point connected to ground, technically bringing Tsec1's start at negative voltage with respect to the chassis, and Tsec2's end at positive voltage with respect to the chassis. You would have successfully made a (rather inefficient and terrible) dual rail/voltage supply. Tsec are your secondary windings.
The reason it'd be a bad one is that this will most likely end up burning your BR diodes out, due to imbalanced current, if you use the split supply at all.
If you do not need the split supply / half voltages, put the windings in series and isolate the center tap. It effectively works as one coil of double the length now.
The image that @euro21 posted depicts parallel operation of the windings.
I hope this helps you somewhat!
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Here's all you need to know: https://www.hammfg.com/electronics/transformers/rectifier
If you use simply tape off the centre tap and ignore it, you will have twice the voltage and only 62% of rated current when using a capacitor input filter as using the centre tap and two diodes.
If you use simply tape off the centre tap and ignore it, you will have twice the voltage and only 62% of rated current when using a capacitor input filter as using the centre tap and two diodes.
Interesting and loosing me a little.
So this trafo is 35-0-35 and was hoping to get approx 50vdc. It's for a power amp so I want all its current. Not sure this is going to work for me.. atleast for the class d amp I had in mind . Might be better to use it as a dual rail and feed a solid state +/-
So this trafo is 35-0-35 and was hoping to get approx 50vdc. It's for a power amp so I want all its current. Not sure this is going to work for me.. atleast for the class d amp I had in mind . Might be better to use it as a dual rail and feed a solid state +/-
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35 + 35 = 70. 70 times .71 = 49V.
So use the Full Wave version above, the bridge version will make 100V.
Real life the voltages will be lower from the load... I'd expect about 42V - 45V when loaded depending on how many VA the transformer is and how large of a cap you plan to use...
If you have basic testing equipment (like a DMM), you can do a couple of tests of the transformer and plug the details into PSUD2 and see what you get.
https://www.duncanamps.com/psud2/
So use the Full Wave version above, the bridge version will make 100V.
Real life the voltages will be lower from the load... I'd expect about 42V - 45V when loaded depending on how many VA the transformer is and how large of a cap you plan to use...
If you have basic testing equipment (like a DMM), you can do a couple of tests of the transformer and plug the details into PSUD2 and see what you get.
https://www.duncanamps.com/psud2/
