Snubbers Work!

[cbb1962]

After I got my machine up and running I had an intermittent issue where Acorn would lose communication. CNCKeith sent me a replacement BBG and it helped the issue but it didn't go away. I began to notice that the communication error always happened after an e-stop, about every fifth e-stop would cause an error. I was talking to Keith and told him that the problem was better, but wouldn't go away and that it happened after an e-stop. He asked me if I had snubbers installed on my motor contactors...

Per the forum recommendations, I ordered a set several weeks ago but hadn't installed them yet. Well, I installed them and literally moved and e-stopped my machine 50 times and not one comm error! Snubbers WORK!

[slodat]

They are super important. Even at a low voltage like 24vdc, the counter EMF produced when the coil is deenergized is significant. And the voltage level is often higher than the supply, for the very brief amount of time it takes to collapse the magnetic field in the coil. In a similar way, we do a DC resistance test on very large (260MVA per phase) power transformers. If you don't discharge through a resistor, the counter EMF will knock a guy flat. Modern test gear takes care of this automatically. It really drove the point home for me seeing this.

This will also pit/ruin/weld contacts rather quickly.

Nice work!

[cbb1962]

Well, it happened again... I e-stopped with the spindle running and lost communications. In my testing, I didn't have the spindle on. I did additional testing with the spindle on, and no comm errors.

Ideas???

[slodat]

Yes. Check out Tech Bulletin 206.

The important thing is you want the snubber installed across the coil. Not the contact operating the coil. In your photo it looks like the coil connections are on the top of the contactor, labeled A1 and A2.

Do you have a schematic showing what you are doing with those contactors?

[cbb1962]

Here is a schematic: A1 and A2 are the 220vac control wires.

[slodat]

In your photo you have the quencharc connected across a normally open contact. The quencharc needs to be across the coil A1/A2, which is on top of the contactor in the photo. They aren't working because they are not across the coil.

[tblough]

Snubbers/varistors/RC networks/diodes/quench arcs should be installed across ANY inductive load - that includes relay coils, fans, transformers, solenoid valves and anything with a coil of wire in it.

[martyscncgarage]

Snubbers/varistors/RC networks/diodes/quench arcs should be installed across ANY inductive load - that includes relay coils, fans, transformers, solenoid valves and anything with a coil of wire in it.

And I will add LUBE Pumps....been there done that....

[frijoli]

Well, it happened again...

Ideas???

Snubbers are wired incorrectly for one. Snubber goes here

[martyscncgarage]

Well, it happened again...

Ideas???
download/file.php?id=9147&t=1

Snubbers are wired incorrectly for one.

Picture is so small I can't see it.
Snubber go across the relay coil terminals of EACH relay or device.