Wich Suppression Capacitor to block Mains emi?

[samsagaz]

Hi guys, i want to know if need to have some special care when choice an capacitor to use between AC Mains to Block some EMI.

i want to know if need to have some special care about brands or sizes, for example any small value will be OK?

Material? Polyester? Polypropilene?

Value?

0.1uf
0.068uf
0.047uf
0.022uf
0.015uf
0.01uf
0,0068uf
0,0047uf
0,0022uf
0,0001uf

Any will works?

[00940]

You cannot use any capacitors on the mains, read this first:

http://www.evox-rifa.com/technote_pdf/rfi_fact.pdf

[samsagaz]

Sorry for the long delay....

I understand, i need to use it after the transformer

im using this design



What about values?

0.1uf
0.068uf
0.047uf
0.022uf
0.015uf
0.01uf
0,0068uf
0,0047uf
0,0022uf
0,0001uf
Any will works?

Wich is the best material of these caps?

Im talking abt C3 C4 and C5. These schematic say 100nf, but maybe other value will be better (or cheaper).

Thanks in advance,

[Atilla]

If you want to block EMI, get an EMI filter, or a socket with integrated filter. Tthat's the easiest way and they're not expensive. Or salvage one from an old PC power-supply, they often come as a separate small board.

Generally, it's 1 X-rated cap between Live and Neutral, 2 Y-rated caps between Live-Ground and Neutral-Ground (sometimes those aren't used, like in the case of double-insulated equipment) and a Common-mode choke.

Something like this is your safest bet, especially because it comes encased in a metal, grounded enclosure:



A simple cap after the trafo won't do you way too much good in that regard.

[jtwrace]

or build one of these:


Common Diff. DCR Volt. Amp.
Mode L Mode L
P3717-AL 25.0 1000 0.30 1500 3
Q4007-AL 4.5 150 0.06 1500 5
Q4018-AL 1.5 35 0.02 1500 10" Logged

Coilcraft - RF chip inductor, power inductor, power magnetics, and other inductors

I'm getting read to build mine. I have the PCB already. Just waiting on some parts.

BC1587-NDCAP FILM MKP .01UF 440VAC X1 20%

220BC1588-NDCAP FILM MKP .1UF 440VAC X1 20%

320BC1589-NDCAP FILM MKP 1UF 440VAC X1 20%

Thread I learned it from is here: Felix project

[jtwrace]

Thought I would add this Vishay Cap PDF as too.

[richie00boy]

Originally Posted by samsagaz

Sorry for the long delay....

I understand, i need to use it after the transformer

im using this design

TNT design pic

What about values?

Wich is the best material of these caps?

Im talking abt C3 C4 and C5. These schematic say 100nf, but maybe other value will be better (or cheaper).

Thanks in advance,

You may as well use what they show, as the only way you will improve is to use proper EMI measuring equipment.

[Sch3mat1c]

Originally Posted by 00940

You cannot use any capacitors on the mains, read this first:

http://www.evox-rifa.com/technote_pdf/rfi_fact.pdf

404 error.

Ehh? X2 caps are specifically rated for across-the-line duty. You sure as heck can put caps across the mains.

Value depends on frequency and current being filtered. This only matters for SMPS supplies, to prevent conducted noise into the mains. Noise going from line to load is negligible because it's well filtered by design. In your case, the transformer and filter capacitors take out any RFI you could ever worry about.

Tim

[WuYit]

Hi,

[samsagaz]

wich will be the diference between Felix project and the one that WyYit Post it?

using components in the mains or just in the secundary, or in both places!