How can i obtain 24VDC@2A from 380VAC or 550VDC. May be i can do it from a one phase system which has one live(220VAC) and one neutral line. But i'm not sure, how to obtain from a three phase system which have three live (220VAC line to neutral and 380VAC from line to line) lines and no neutral. (Actually there is neutral but the system won't contain neutral input).
50VA (for dc/dc ≈24V @ 2A) step-down toroidal transformer can be as small as 80mm in diameter and 30mm in hight. Is it still to big?
You can find toroidal 50VA transformers (off-the-shelf) in the following configuration:
Primary: 230Vac
Secondary: 2 x 55Vac
If you connect this transformer with all windings connected in phase in series you will have 340Vac auto-transformer, and that is not far away from 380Vac. You can use then 230V (the former primary) as the supply for your 230/24 smps..
Regards,
IanP
May be at the limits. But i think, there should be applications that obtain low voltage dc from high voltage dc via switch mode technique. I think this should be more convenient but more difficult. What i'm looking is making this a bit easier for me by getting your opinions. But i will keep your suggestions in my mind, thanks
You may consider 'offline smps'. It's possible to find Integrated Off-Line Switching Regulator (e.g. NCP1000, NCP1001, NCP1002, etc) that can function in continuous operation over a wide range of inputs, from 85 Vac to 265 Vac. But 380Vac... err.... may be you still need a step down transformer from 380Vac -> 220Vac...
you can make a halfbridge converter with each mosfet rated for around 600 to 800
volt. The input filter can be made using 2 nos. 350 vdc caps in series.
But take care as the voltage is on the higher side.