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Power relay contact arcing

  1. Mar 13, 2015 #1
    DPST Power relay has 120VAC coil & 40A contacts (resistive) ratings. A Fuji PXR4 Micro Controller is triggering the relay; the load is a 220V pottery kiln element. The contacts are arcing (but not bouncing) at make & break on nearly every cycle. The above relay just replaced a previous SPST relay which experienced the same arcing with also some bouncing - which eventually pitted the contacts.

    Is there something to be added to reduce/eliminate the arcing?

  2. jcsd
  3. Mar 13, 2015 #2


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  4. Mar 13, 2015 #3
    Thanks Dave, but my Fuji controller won't talk to SSR's. A fuji model that will, costs ~ $200. That's a "swapmeet" I can't afford to go to! :-(
  5. Mar 13, 2015 #4


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    what is the type/style/voltage etc output of the controller ?
  6. Mar 13, 2015 #5
    Gordo, What exactly do you mean by pitting the contacts?
  7. Mar 13, 2015 #6
    Fuji Micro Controller #PXR4-RAY1-4VoA1 : Power: 100 - 240VAC Measured Value Input: Thermocouple (Type "K" ) Control Output: Relay
    Fuji Micro Controller #PXR4-RCY " * * : Solid State Relay
    the "C" in the 6th digit position indicates Solid State Relay in the "Control Output".

    I've been in touch with Fuji on this: Thinking that all the model's features are "setable" like the dozens of other options. This feature is fixed....therefore the "A" or "C" (in the 6th digit position of the controller number) must be selected at time of order. I purchased this Model "A" in 2/2/2007. SSR (model "C") was a lesser deal then, therefore much more expensive then.

    I just have to believe that there is a simple combo of capacitor, resister, diode, gizmo, whatever, that will moderate the shock (eliminate the arcing) of the make-break load on the DPST relay.

    Thanks for your interest,
  8. Mar 13, 2015 #7
    contacts that are burnt - pitted, eventually to "weld".
  9. Mar 13, 2015 #8


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  10. Mar 13, 2015 #9
    Is the pottery kiln have an inductive element?
    As you mentioned you could try using a RCD or just a RC snubber.

    Why can't the Fujitsu Micro drive SSDs.
    There are SSDs available down from 3.3VDC to 220VAC
  11. Mar 13, 2015 #10


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    You may need a two-stage relay. Use the existing relay to trigger a second relay with a higher current interrupting rating.

    But first discard and replace the relay with pitted contacts.
  12. Mar 14, 2015 #11
    Yes, AC. Looks like the industrologic link will help with adding R &C contact protection. Thanks for the help. This forum is really sharp.
  13. Mar 14, 2015 #12
    Thanks for the ideas. I'll try adding the R & C "protection" - first.

    Replacement = done. See my #1 post.
    Last edited: Mar 14, 2015
  14. Mar 14, 2015 #13
    Thanks for the notes.
    It's resistive. My impression: "less than industrial sized", and perhaps all pottery kilns are resistive......like oversized toasters. I've use mine to warm bagels.
    Yes, Fuji Electric Systems Company makes controllers that drive SSR's. See my #3 & #6 posts.
    I appreciate all the help. I'll use it now to do my homework.
  15. Mar 14, 2015 #14

    jim hardy

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    Big loads just make lots of sparks.

    40 amp rated contacts should last for thousands of cycles, unless that kiln is huge. You didn't say what is its current draw.

    220 volts at 40 amps is 8.8kw

    http://www.te.com/content/dam/te/global/english/products/relays/catalogs/files/powerrelaysbook/c0-v4bg-4.pdf [Broken]
    Last edited by a moderator: May 7, 2017
  16. Mar 15, 2015 #15


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    After looking at the specs for the -ray1 and the -rcy1 the only difference is that the ray1 has contact output control (you supply power to the contacts) and the rcy1 supplies 24vdc output for a solid state relay.

    If you purchase a solid state relay with a 90-280 vac control and rated for 40+ amps (sorry if I did not see your load current in any above posts) it should just replace your contactor directly. I believe this will work, http://www.crydom.com/en/Tools/parametric-search.shtml?type=panel. If not just input your parameters and it will give you a part number. I've used crydoms for years with excellent results.
  17. Mar 15, 2015 #16
    I'll reply to Jim & Wirenut here. I really appreciate the interest/help from everyone on this thread. First, I'm confused....I'm hardly up to speed on this technology.

    The kiln is 220VAC 20A - 4.4kw Yes, my Fuji PXR4-RAY1 .....the control output supplies only a signal to the 120VAC coil of my Grainger Magnacraft #6CUR4 (DPDT 40A Resistive. Fuji tech has advised that to run a solid state relay I need their RCY1 Controller. BTW, on the back of both units, taps #5 & #6 - RAY1 connects to the coil of the mechanical relay (Grainger) & RCY1 connects to a 24VAC or DC SSR .

    I'm confused. Wirenut, do I understand that there is a SSR that accepts a 100-240VAC output signal from my RAY1 (it contains a relay - the RCY1 does not) & hence switches a 220VAC 20A line load (every 2 minutes for 11 hours - the contacts remain closed aprox 15 sec. each 2 min)? I'll check the crydom.com link; perhaps that will help me understand equip ability/availability.

    Thanks, Gordo
  18. Mar 15, 2015 #17


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    No wonder it eats relays!
  19. Mar 15, 2015 #18


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    As long as you between 90vac and 280vac the part I gave you will work.
    All this solid state relay is is a mechanical relay without moving contacts, but electronic components
    to control the current flow through the output.
    The only thing I think I forgot to say is for the 220volt output you should use 2 (one for each line), and just put the control
    power to each of them in parallel.
  20. Mar 15, 2015 #19


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    After looking through the Grainger catalog these parts should work (remember you will need 1 for each line) 1DTG8 OR 1DTG3 , the only difference
    being one has a minimum output voltage of 24v and the other is 48v. Your output voltage is 220v.
  21. Mar 15, 2015 #20
    Nothing good snubbering can't deal with.
    In high power applications, even without dominant inductive loads, snubber circuit is necessary to protect switch/relay from HV surges/excessive arcing during switching actions. It is strange to me if the relay you have is sold without snubber circuit. If it comes with snubber and arcing is still significant, than the relay is inadequte for the load. In the case of high inductive loads (like motors) I would always prefer snubber circuit be put in parallel to the load rather than parallel to the relay contacts. In your case this needs to be analyzed.
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