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It's common practice with transformers WTP Pepper. Voltage is always measured open circuit.
Please help me to build step down transformer 220 to 12-0-12 volts 1.5 x 2.5 bubbin. what number of turn to 220 volt primary and wire size to secondary 12 volts. 40 to 50 amperes.
I believe he said he wants both + and - 15V @ 5A per side. Tht's a total of 150 Watts of load power, VA rating on the transformer would be more like 250VA or higher to power both outputs and allow a small drop over the linear regs. The RMS transformer secondary current is about 1.5X DC load current with FWB diode/cap design.hi,
The 120VA transformer will not provide a 5Amp output, closer to 3Amp.
A rough transformer VA , would be 30V * 5 = 150VA, also you should allow for the voltage drop in the regulators, say 3V.
That would require a 36V * 5 = 180VA transformer.
Correct, with resistive loading delivering rated RMS secondary current.This is not what I have found, commercial transformers are quoted as the rated outed voltage at the rated current, otherwise the ratings quoted would be meaningless.
At that current, you need thick copper foil.Better you start your own thread.
Be ready to buy a lot of copper wire.
Be advised you will need massive heatsinks for this, and the design is not feasible for full current at low output voltages. At say 2V output at 5A load, you would have about 16V drop across the linear reg which would be about 80W. That exceeds the safe power dissipation for any monolithic linear reg. The one you called out specs 1.5C/W thermal junction to case, add another 0.5 for mount to the heatsink that means 80W will raise the junction temperature 160C above ambient even with an infinite heatsink. Design not feasible.After googled I have made a circuit attached hear with. please verify and and make suggestions if any to improve the circuit. I have made the circuit to suit 15V, 5Amps which will serve my purpose.