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?
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?
You cannot use any capacitors on the mains, read this first:
http://www.evox-rifa.com/technote_pdf/rfi_fact.pdf
http://www.evox-rifa.com/technote_pdf/rfi_fact.pdf
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,
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,
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.
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:
An externally hosted image should be here but it was not working when we last tested it.
A simple cap after the trafo won't do you way too much good in that regard.
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
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
Attachments
You may as well use what they show, as the only way you will improve is to use proper EMI measuring equipment.
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
You can buy in EMI filters.
I modified one to work with some equipment.
Here is the cct diagram.
The capacitors must be X2 (to L+N) and Y2 (to earth) if i remeber correctly.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Pretty much, yes. You can see the schematic on the back of the socket on that image above. And you wouldn't have to worry about reading and following all the safety requirements. It is good to know them though. But to save you time and trouble, get a decent EMI filter and you're done.
That one is definitely better. Just take care of proper safety measures when doing mains-related stuff. Case it in a small, grounded, metal box. If you plan on including MOVs/gas-discharge overvoltage protectors, keep in mind that one won't be enough. They can only handle a few surges before becoming ineffective.
Also against UK and European electrical safety regulations. Can't remember ever seeing 2u2 in Y rated either. 2n2 is pretty much the standard value.
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