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Relay with High DC Breaking Capacity

  1. Aug 6, 2017 #1
    Hello!

    I have to use a relay to operate circuit breaker opening/closing coil i.e. 80W @ 110VDC.
    Since the breaker is having some mechanical interlocks, so sometimes when the coil is operating, the breaker may not open. In that case the relay contact has to make & break the opening/closing coil supply.

    I initially used normal relay for this operation, but later on I observed that relay is not more functional, when I open the relay (i.e. removed its plastic case), I found the plastic base of the relay poles was melted and when the relay was operating, there was some gap between pole and through.

    After studying the issue, I came to the conclusion that the DC Inductive Breaking capacity of the relay I were using was 35W Inductive Load i.e. DC12 L/R = 40ms, while the coil rating was 80W.

    I search the relays from different vendors, but only 1 relay found suitable for this application, i.e. Arteche CD-2XR relay with high DC Inductive Breaking Capacity.

    Apart from this, we can use some other techniques to achieve High Inductive DC Breaking, as mentioned below.
    1. Use Two contacts in series
    2. Use Diode across the Relay Contact

    Is there anyone who has gone through such problem?
    Is there any other brand or relay to use for such High DC Inductive Breaking Capacity?
    Is there any other technique to handle this issue?

    Regards,

    Farhan Ali
     
  2. jcsd
  3. Aug 6, 2017 #2

    jim hardy

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    Last edited: Aug 7, 2017
  4. Aug 6, 2017 #3
    For an inductive load you would need a contactor with a sufficient AC-3 rating for your application, the link (http://electrialstandards.blogspot.co.za/2014/04/electrical-contactors-utilization.html) has a short explanation regarding AC ratings.

    Industrial suppliers like Siemens, ABB, Schnieder Electric, etc will have massive ranges of such devices for you to choose from, I'm sure if you gave one of them a call they would be able to offer you the correct product.
     
  5. Aug 6, 2017 #4

    davenn

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    Last edited: Aug 6, 2017
  6. Aug 6, 2017 #5

    CWatters

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    I think the OP means the relay is switching an inductive load.
     
  7. Aug 6, 2017 #6

    davenn

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    yes
     
  8. Aug 6, 2017 #7

    jim hardy

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    I think the term for relays in that service is "Pilot Duty Relay"

    ?? Inductive load so arcing is when contact opens.
    http://www.panconcorp.com/PDFs/capacitors/QRL-Quencharc.pdf
    upload_2017-8-6_21-2-45.png

    Agreed 100 % .
     
  9. Aug 7, 2017 #8

    CWatters

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    Clamps the inductive spike to the DC voltage?
     
    Last edited: Aug 7, 2017
  10. Aug 7, 2017 #9
    The diode would have to be across the Circuit Breaker's closing/opening coil, not the relays coil.

    But ideally you need a relay with contacts rated for the DC voltage and current, AND inductive load. For an air insulated contact it may have an arc chute with blowout coil, there are vacuum and solid state relays for this purpose as well.
     
  11. Aug 7, 2017 #10

    jim hardy

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    Well yes of course it would. Sorry i didnt make that clear

    old jim
     
  12. Aug 7, 2017 #11
    Not sure if someone was being pedantic - :wink:
     
  13. Aug 7, 2017 #12

    jim hardy

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    OOPS now i see my mistake

    I sure 'nuff typed " relay " while thinking " breaker " .

    Apology hereby extended to all...
     
  14. Aug 7, 2017 #13
    I was not referring to you Jim, but the others... cheers
     
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