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I want to make a 70 VDC power supply, output unregulated with +/- 10V variation allowed. I also want 50 A current from it. My input can be 3-phase 380 V mains supply.

I cannot think of a 3-phase transformer for this power supply that can give me 70 VAC at the output. How is it possible to wind this type of transformer?

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  • \$\begingroup\$ Make your mind up 70 VAC or 70 VDC? \$\endgroup\$ – Andy aka Jun 19 at 16:50
  • \$\begingroup\$ The transformer will output 70 VAC and then i will rectify it to 70 VDC. \$\endgroup\$ – homecloud Jun 19 at 16:52
  • \$\begingroup\$ At that power you should design it to have power factor correction. No, there isn't a 3 ph to single ph transformer that does this. You will likely have to use a three phase rectifier and a powerful DC to DC converter (if you don't care about power factor correction) or use a bespoke power supply. \$\endgroup\$ – Andy aka Jun 19 at 17:08
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For a 70 V DC supply with a capacitor filter, the AC RMS voltage should be about 52 volts. If you use a 48 volt transformer, that would provide about 65 volts allowing for voltage drop in the 3-phase bridge. It is certainly possible to wind a transformer for the voltage that you need.

Rather than power factor correction, you might want to consider harmonic current reduction. Harmonic currents cause reduction in power factor, but the correction method is different.

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