+12v, 100mA DC Power Supply design from 3-Phase

[Briez]

Hello,
I want to design +12v, 100mA power supply from 3-Phase without transformer. I mean to say that if i can use High Frequency Metallized Polypropylene Film Capacitor 155J 440V in all three phases and can give input to rectifier then can i get 12V, 100mA output?


Can any one suggest me circuit design of 12V, 100mA power suppy using High Frequency Metallized Polypropylene Film Capacitor 155J 440V from 3 phase?

High Frequency Metallized Polypropylene Film Capacitor 155J, 440V is shown in picture.

 

[chuckey]

If you have a neutral wire its a good idea - only 250 V from phase to neutral, also neutral can be your common (-?) line. Without a neutral , I do not think it is possible, unless you tie your output common line (- ?) to one phase which is extremely dangerous or you rectify the three phase to DC, then drop it down to 12V!
Frank

 

[Briez]

If its possible to drop down 3 phase line voltage to 25v ac then i can convert it to DC 25 by rectifier. But how can i drop down it to low voltage by High Frequency Metallized Polypropylene Film Capacitor 155J, 440V?

And what will be its current?

 

[chuckey]

You could try to establish a phantom neutral by connecting three capacitors to a common point with each capacitor going to a live phase. If the phase voltages are equal and the capacitor values are the same then the point would be at 0v, however with your +- 10% caps, this 0V point could have up to 60V AC on it.
Your capacitors are marginally rated for 440V, you should use 600V caps. The failure of one of these caps , going short circuit is dangerous , it could put a 440V mains voltage on your 12V line. feed each capacitor via a 50 mA 440 fuse and a 1K ohm resistor (to limit the inrush current to your reservoir capacitor). Use a zener diode to clamp the rectified line to a safe voltage to allow the fuse to blow in the event of a failure.
By the time you have bought all the high voltage capacitors (6) and fuses, it would be cheapper and better to use a transformer.
Frank

 

[Briez]

Thank you so much. . .

I will try to use transformer...

Actually i wanted to design cheaper power source for my microcontroller and +12V relay. what should be the transformer rating according to it?