I have a transformer with 5 wires. Two mains, a centertap and the two hot wires. 2x27 VAC
Can I wire it and the rectifiers/caps in a way that I get 27x1,41~1x38 VDC with as much current as possible?
Can I wire it and the rectifiers/caps in a way that I get 27x1,41~1x38 VDC with as much current as possible?
you could use a full wave rectifier (two diodes) but the current capability will be severely compromised..
Why not parallel the secondaries to double the current at 27vac? Perhaps I misunderstand your question...
Since it is a center tap and I can't access the two windings seperatly I don't know exactly what to do. If I put the two hot wires together I'm pretty sure there will be a fire since they are out of phase.
Double full-wave bridges with outputs connected?
Double full-wave bridges with outputs connected?
Pardon me, you are correct, here in the US, most of the new Toroids come as dual sec windings which you rig up for Center tap OR parallel connection. I do know that some are hardwired as a center tap. I just made a few Toroid connections in my projects and was in "that" frame of mind.
Cheers.
Cheers.
I'm used to transformers with seperated wires too, but this one is free so I can't complain. Worst case scenario is that I have to open it up and see if I can get another wire out of it.
I found a webpage
that gives formulas for different possibilities
to make DC out of transformer.
Formulas is to decide what is minimum rating for trafo
when you need a specific DC voltage and max current.
These formulas can be rewritten to give you resulting DC voltage
and max Current for a given Trafo and method of rectifying.
Also if you use a filter capacitor will effect result.
Transformer VA Calculations
that gives formulas for different possibilities
to make DC out of transformer.
Formulas is to decide what is minimum rating for trafo
when you need a specific DC voltage and max current.
These formulas can be rewritten to give you resulting DC voltage
and max Current for a given Trafo and method of rectifying.
Also if you use a filter capacitor will effect result.
Transformer VA Calculations
I have a shield copper-foil layer on the primer, and the core has also a wire for grounding.
Where should I connect these wires ? To the earth on the primer side, or to the GND on the secunder (DC) side ?
Where should I connect these wires ? To the earth on the primer side, or to the GND on the secunder (DC) side ?
Hi Johnny,
your post6 hit it precisely.
Open up the secondary and separate the two windings. Accurately measure the open circuit voltage of each to check if they match. An antiphase connection for test purposes will give almost zero volts out. Add a turn or two to the lower voltage winding to try and get best matching.
Once this is done you can parallel the two secondaries.
If the matching is not too precise then rectify each separately and then parallel, even adding a small value power resistor (0r1?) to each line out to force better current sharing (just as you do for Re in multiple output stages).
your post6 hit it precisely.
Open up the secondary and separate the two windings. Accurately measure the open circuit voltage of each to check if they match. An antiphase connection for test purposes will give almost zero volts out. Add a turn or two to the lower voltage winding to try and get best matching.
Once this is done you can parallel the two secondaries.
If the matching is not too precise then rectify each separately and then parallel, even adding a small value power resistor (0r1?) to each line out to force better current sharing (just as you do for Re in multiple output stages).
What would a safe wattage be for powering up 2 LM3886s (max output 11A each) at 35V through 8ohms load, with these resistors... I have measured all my trannies and none of them are even close (in my opinion) to have equal secondaries.
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