Best RC snubber

[Peter Kiproff]

I have a hydraulic valve on a break press, 115V approx 1A+ that when opened
produces a nasty spike!

This affects other logic, I tried 47 ohm 1/2 W in series with .1 uf @ 600V.
across the coil.
This is in a remote local.

What would be your best guess to tame this? without scopeing it

should it be across the coil or across the switch or relay?

Thank you for helping.

Peter

 

[John Popelish]

Peter Kiproff wrote:

I have a hydraulic valve on a break press, 115V approx 1A+ that when opened
produces a nasty spike!

This affects other logic, I tried 47 ohm 1/2 W in series with .1 uf @ 600V.
across the coil.
This is in a remote local.

What would be your best guess to tame this? without scopeing it

should it be across the coil or across the switch or relay?

Thank you for helping.

Peter

The wiring to the coil may be as much of the problem as the coil,
itself, since it may be acting as the antenna.

I would want to wire the coil with a pair of wires that came back,
together, to the contact that drives it, and put the snubber device
across that pair, right at the contact. This will slow the rate of
rise of voltage all the way to the coil, including the wires.

Your snubber values are reasonable, but you might want to lower the
resistance a bit. Say, 22 ohms. This will still limit the worst case
turn on current spike to about 5 amperes which should do little damage
to most relay contacts. You might also want to parallel the capacitor
with an MOV rated for 120 volt AC service, to make sure the inductive
pulse does not force the voltage above the capacitors rating.

--
John Popelish