Hi, I have been fighting with a noisy pump that is switched by a relay. I have decided to give a RC snubber across the pump a try to see if it will quite it down. I'm however having some difficulties calculating the Capacitor and Resistor values.

Here is what I have:
I = 2 Amps
V = 120V
R = V / I = 60 Ohms ??
C = ??



I tried to follow this pdf but it was a little over my head http://www.cde.com/tech/design.pdf. I also tried the ehow article http://www.ehow.com/how_12030206_design-rc-snubber.html but it seemed like they dummied it down to much plus their math doesn't seem to work.

 

What type of noise?

 

Instead, put the RC snubber across the relay contacts. Typical snubber values are 0.1mf. & 100 ohms in series.

Cheers, DPW [Everything has limitations...and I hate limitations.]

 

Use a capacitor rated for full ac line voltage.

 

Thanks for the responses. I believe it to be EMI as it's radiating over all the lines and jumping opto-couplers on the other side of the relay.

I came across this document and Excel file that seems very helpful.
http://www.hiquel.com/fileadmin/userfiles/AppNotes/Englisch/HIQUEL_Snubber_AppNote_EN_0100.pdf
http://www.hiquel.com/fileadmin/userfiles/AppNotes/Englisch/HIQUEL_SnubberCalculator_AppNote_EN_0100.xls


I put in all the numbers in and it's recommending:
C: .1 uf
R: 600 Ohms

I have a 600V .1uf Capacitor on hand so I'm good there.

It's also suggesting a 2.5 Watt resistor, with a Max peak voltage of 1716V. I can't seem to find a Carbon Composite resistor beyond 1 watt though. There seems to be some wirewound ones though. I'm a little lost on which type I should be picking for this purpose?