1 or 2 dedicated 120VAC circuits for my CNC?

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29 Nov 2022 01:17 #257925 by tommylight
Never used them, but from the above spec i really do not trust Eaton, at all.
Notice how the Fuji rated current drops with the rise in voltage, Eaton does not.
Since you are using a single phase, you can always parallel relay contacts for more current.
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29 Nov 2022 01:23 #257926 by spumco
RELAYS
Yes, you've got it correct with #8 being DC+ and #7 is DC-
You'll find that there are a few different relay contact numbering schemes used worldwide.  The symbols I used don't really follow a numbering scheme because I'd need 3 or 4 different symbols for each relay type in my wiring diagram library to cover all the numbering schemes.

But if you look closely at the picture on the relay (and I think you did) you can see the pairs of NO/NC contacts along with the COM, plus the coil connections at the bottom.  The coil diagram looks a little odd because they've drawn a flyback diode as well.

CONTACTOR
The Eaton is rated for 15.5A regardless of voltage, so go with that one.
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29 Nov 2022 01:25 #257927 by spumco

Never used them, but from the above spec i really do not trust Eaton, at all.
Notice how the Fuji rated current drops with the rise in voltage, Eaton does not.
Since you are using a single phase, you can always parallel relay contacts for more current.
 


DOH!

Why not Eaton?  I've haven't used a ton of their stuff, but I've got two VFD's and some other components doing OK.

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29 Nov 2022 01:28 #257928 by spumco

 As you've probably discovered already, everyone has their own opinions about what to do. 
 


Q.E.D.

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29 Nov 2022 03:42 #257935 by Sray69

The coil diagram looks a little odd because they've drawn a flyback diode as well.

Apparently this particular relay includes...
  • LED indicator for monitoring operating status and diode surge suppression for limiting voltage spikes
Not sure if that is good or bad in my situation? I assume it should work fine?

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29 Nov 2022 03:45 #257936 by spumco
It's good in every situation.  LED is optional but nice, diode is required in many cases to protec whatever is triggering it (i.e. Mesa).
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29 Nov 2022 03:53 #257937 by Sray69

Notice how the Fuji rated current drops with the rise in voltage, Eaton does not.

Yes I noticed that and was curious why? So is your take on it that they are not posting accurate numbers? I see this all the time with Chinese stuff but I was under the impression that Eaton was a pretty good company.

Since we are on this subject can you guys give me your opinion on which companies are the better ones to look for in the electronics industry? Here are some of the brands I see all the time, at least in the relay/contactor category. If you have others that you would recommend that would be great. 
  • Dayton
  • Schneider
  • Eaton
  • Fuji
  • Allen Bradley
  • GE
  • Siemens
  • Sprecher + Schuh
  • WEG
  • Omron

Since you are using a single phase, you can always parallel relay contacts for more current.

That is interesting. So does this double the current, or is there a calculation to determine what it would be?

Thanks

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29 Nov 2022 04:21 #257939 by spumco
My opinion - subject to change if Tommy tells me I'm all wrong...

All the companies listed are fine.  Some are significantly more expensive when new than others.  And there are plenty of other 'top-tier' or nearly top-tier component OEMs.  I'm sure there are dozens I've never heard of, much less used or seen.

You want another rabbit-hole homework assignment?  Go to HGR Surplus's site, and search for "enclosure" or "control" or similar.  They've got tons of used industrial electrical & electronics stuff, and if you zoom in on the photos you can start to get an idea of what people use when money is no object.

Look at the CNC machines and other automation equipment and check out the close-ups of the control cabinets.  Ignore the drives & VFD's - look at the relays, contactors, power supplies, and other 'commodity' components.

Same thing for motion hardware.  Hi-win linear rails appear to be the cat's meow in the hobby/printer world compared to no-name ebay stuff... but you won't find them in frequently in industrial equipment.  THK, Bosch-Rexroth, IKO, Thomson Linear, and others never found on a 3D printer.

Keep in mind that the brands you come across are regional.  Lots of Allen-Bradley over here, Siemens, AB, & others in Europe.  Mitsubishi Electric for Japanese equipment.  It varies, and some equipment manufacturers stick with suppliers they know even if they could save money with a perfectly good substitute.
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29 Nov 2022 04:24 #257940 by spumco

 

  • Since you are using a single phase, you can always parallel relay contacts for more current.
    That is interesting. So does this double the current, or is there a calculation to determine what it would be?

    Thanks


That one's beyond me.  I don't know if I've ever seen a rating for individual contacts or how the rating is determined.  Is a "20A" contactor good for 20A per contact, or 20A shared between all three (or 4 or 2)?

Good question.

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29 Nov 2022 12:45 #257964 by tommylight
@ Spumco,
You forgot NSK! :)
They are top tier for linear rails and ballscrews, still made in Japan.
I see them on really expensive machines made to run 24/7/365.
THK seems to be on paar with them.
Yes, you can parallel relay contacts, and they are rated for single contact current.
Many plasma cutters use paralleled relay contats to switch the high current on and off, always when pilot arc is HV or HV/HF.
@Sray,
All the manufacturers you mentioned are good, except Dayton and Eaton that i never used or seen used so for those Spumco is a much better refference since he has experience with them. Of the rest Schneider is a bit cheaper, Omron is top notch, i have used propably over 500 Omron relays by now, even used ones never fail.
The issue with relay contacts and current/voltage ratings is the ability to switch off and prevent arcing. High current/voltage relays and switches have built in arc suppressors.
Not an issue with home voltages and currents. And as a general rule, all of those will work with a bit higher current than rated, just do not push them to far. I would guess 20% more current is OK, but it will shorten the contact life span, probably by quite a bit.
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