1:3 transformer for low voltage

That's not quite enough information - mains transformers are rated by voltage and VA (i.e. 20V to which winding and it it step-up or step-down? total VA is what (20V x 5A = 100VA??). I'd be surprized if you get one that's not rated for an actual mains voltage, such as 110V or 230V...
 
I drew the circuit I would like to make.

Realistic?


EDIT: not 12V but 15V.
 

Attachments

  • scan.jpg
    scan.jpg
    125 KB · Views: 36
Last edited:
So 15VA output at 15 V in at mains frequency. The AliExpress link is for SCR trigger transformers, which are high frequency ferrite cored, so completely unsuitable. You need silicon steel lamination construction to go down to 50Hz at significant power. The problem is there is no demand for 15V mains transformers, so its unlikely anyone makes something that low impedance at that sort of power that can go down to 50Hz. You could take a 120V input 40V output mains transformer that's rated at 25A output, then the impedances are similar, but that would be a 1kVA monster!

Sounds like a custom winding job.