snubber circuit design
snubber circuit design
(OP)
I'm using a low cost VFD in a hoist application. I am controling the drive with some small ice-cube (120vac) relays. I need to eliminate any potential noise from the relay's coil. How do you size the R and C?
thanks in advance.
thanks in advance.





RE: snubber circuit design
RE: snubber circuit design
RE: snubber circuit design
http://www.littelfuse.com/ASP/Search/detail.asp?ID=460
If the link does not work, go to www.littelfuse.com and search "MOV."
Maybe something in there will help. I know at least one of the papers compares various devices, including MOVs and snubbers. Best of luck.
RE: snubber circuit design
The Variable Frequency Drive (VFD) may need input filter(s), perhaps R-C or L-C. Also, it may need output filters, R-C or L-C. The filters are passive (can be active too, but more complicated) and mitigate harmonics. There are also EMI input and output filters which suppress the electromagnetic interference. Next, threre are different principles of VFDs available on the market. Please, would you have more information available?
RE: snubber circuit design
There is Chapter 18 "Snubber Network" including
1. Snubber Resistor Value in Ohms
R=Timeoffmin/(2 x Csnubbercapacitorvalue)
Timeoffmin time in microSec
Csnubbercapacitorvalue in microFarads
2. Snubber Capacitance in microFarads
C=Ip x Tf/(2 x 70% Vceo)
Ip is maximum current in Amps
Tf is fall time in microSec
Vceo is rated voltage
RE: snubber circuit design
ASCO solenoid. I used a 47 ohm in series with a .1uf cap
for noise suppresion. The solenoid was completely messing
up my PIC16F628 microcontroller. I tried a MOV at first but
that didn't stop the problem. I also remember using a snubber
for a pump motor(1/3hp) circuit it ended up being 100 ohms 1/2 w
with a .1 uf cap rated at 200 for a 120 VAC application.
But.. like other posts say it all has to do with the speed of
the wackie pulse. Incidentally the solenoid above was 24vac
and I believe about 7 watts or so,, not very large but it was
twinking out my circuit at both turn on and turn off modes.
The above suppresor completely eliminated the problem.
You can determine the values by trial and error but at least
overrate your components.