Transformerless power suply problem

[dhanajaya]

Dear Sir
I have designed the circuits for 50 HZ ,440 AC voltage i.e three phase . I have done only connecting two phase only like RYB:- RB , BY and RY so I have connected X rated capacitaor 470K/250 volts is series connected with each phase to 5408 diode bridge rectifier circuits to run 0.2 mili amps rely ON like this i am using 3 relays like RB , BY and RY . its working fine but whenever power is failure after the power is come it will damage the circuits . please help me

 

[Dick Cappels]

You probably need some kind of surge current limiting. If the power comes on while the power line is near the peak of the cycle, the current to quickly charge up the capacitor can be huge.

That's the purpose of R1 in the circuit above. Its a fuse resistor but backed up by a discreet fuse because the fusing current of R1 was not known. Also note the Metal Oxide Varistor that limits the peak voltage to R4 and the circuit to the right of it. The bleeder resistors R2 and R3 bleed the voltage across C1 to a safe level when the circuit is unplugged.

In case you are interested in the rest of the article:
http://cappels.org/dproj/Power Failure Light/White LED Battery Powered Power Failure Light.html