[Jackal66]

I am getting started on the power side of my mill. All of my contactors have these small black boxes mounted on the front.

After searching several sites, I can't come up with anything.

Usually that is where the (plunger????) is.


Are these to make a lamp come on when the contactor is engaged? Or prevent the contactor from engaging until something else is kicked in?


I didn't take a pic of mine so here is a modified catalog pic. Can't remember if mine have 1 or 2 wires?



Just checking to see what they were in case it affects how things need to be wired.

JAckal:cheers:

[gthlm]

That's an rc network. I don't know the science behind it, but it's purpose is to stop arcing across the points when the contactor opens and extend the life of the contacts.

[Al_The_Man]

Also see this post.
http://www.cnczone.com/forums/genera...ion_error.html
The type you show is usually across the coil to prevent back EMF spikes appearing on the AC supply to the coil, there are 3 ph types also that go across the 3 phases for the same reason.
The AC snubber in the link, is the equivalent purpose to the back EMF diode for a DC relay/contactor.
Some contactor manufactures supply ones made that will fit right across the coil terminals without any other mounting necessary.
Al.

[bloke]

Also, it's a possibility that they are auxiliary contacts attatched to the main contactor. If you can unclip it, look underneath it to see if it has a plunger. If so, stick a meter across it (without power to the machine) set your meter to ohms and actuate it. if it changes state (opens or closes, chances are it's auxiliary contacts.

[Al_The_Man]

Also, it's a possibility that they are auxiliary contacts attatched to the main contactor. .

That is possible but IIRC that contactor has side mount auxiliaries, if at all.
Al.

[Jackal66]

I'll have to go check and see. Will report back the results. Right now we are in a bad storm.

JAckal

[Jackal66]

Here are some pics of the actual parts in the machine:

These boxes do have 2 leads. They connect to the contacter and the (heater???) where the green arrows show.






You can see the label after I turned one around to take a pic.
These don't have a plunger/switch in them.


Thanks for all of the help.

JAckal :cheers:

[Al_The_Man]

They are RC snubbers .22µf with 100ohm in series, it is a job to say whether they are across the coil or a contact.
The overload contact is often placed in series with the coil.
BTW, modern O/L's do not use heaters but electromechanical type detection.
Al.

[Jackal66]

Thanks Al,

So the lower part is an overload, then.

Should I try to incorporate the RC snubber into the retrofit, or just save them in case there is some sort of problem?


JAckal :cheers:

[bloke]

Those were wired across the coil. They connect to the overload as that had a set of contacts in it to drop the 115v to the coil if the overload tripped.

[Al_The_Man]

Should I try to incorporate the RC snubber into the retrofit, or just save them in case there is some sort of problem?
JAckal :cheers:

Are you keeping the contactors as they are?
But in any event, I would wire the snubbers across the coil terminals, I have seen a few application problems where they required fitting.
BTW, there is a spare N.O. contact on the O/L, I often use these to advise a controller or PLC that a trip has occurred so a alarm message can be displayed.
Saves in trouble shooting time.
Al.