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How increase output current from of a transformer???
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Dhanushka:
Dear all,

I salvaged a transformer from an old Sony stereo audio system. It has 2 x 12 V/2 A (center tapped) and 2 x 20 V/3 A (center tapped) outputs. Can I connect these center tapped winding in parallel to increase the current (4 A and 6 A)? Please tell how can I do this? I mean that whether should I consider the winding direction? 
ledtester:

Zero999:
Connecting the transformer to a biphase rectifier will increase the current capacity a bit, because each winding conducts half of the time, so allows time to cool down, but not by double, as increasing the current by a factor of two, results in four times the power dissipation.

https://www.electronics-tutorials.ws/diode/diode_6.html

If you can access the windings, then you could break the centre tap and connect the two separate secondary windings in parallel, but it's not possible to connect two different voltage windings in parallel, because current will flow from the higher to lower voltage one, causing it to overheat.
Gyro:
I've always found the attached transformer-rectifier circuits guide from Hammond quite a useful quick reference (It used to be in the RS catalogue at one point too)...
exe:

--- Quote from: Zero999 on October 01, 2019, 10:19:31 am ---Connecting the transformer to a biphase rectifier will increase the current capacity a bit, because each winding conducts half of the time, so allows time to cool down, but not by double, as increasing the current by a factor of two, results in four times the power dissipation.

--- End quote ---

My calculations for tranny I have showed almost no benefits from these, as most losses are on primary, and iron losses. Secondary windings have low resistance. This is easy to verify by measuring resistance of windings.

I'd suggest to put windings in parallel (if they have same voltage), that would make it lowest losses, imho.
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