AC rated contacts vs DC rated contacts

Discussion in 'Automotive Electronics' started by witailhntr, Aug 2, 2016.

  1. witailhntr

    Thread Starter New Member

    Aug 2, 2016
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    When contacts are rated for DC can they carry the same AC current? Need a 70+ amp set of continuous duty contacts from a DC relay to carry a 120 VAC with a max 70 A. The relay will be activated with 12 VDC so the coil will be fine, just looking for thoughts on the use of the contacts for this carrying ability.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    As a general rule, the contact conditions required for switching DC are more stringent than AC so they are often rated slightly higher capacity when used on AC.
    Max.
     
  3. JConnor

    New Member

    Dec 15, 2014
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    If you think about alternating current, it breaks the arc with every cycle as the polarity changes. So a DC rating will usually be MUCH lower than the AC rating (eg. 1A DC 24V, 20A AC 300V).
     
  4. tcmtech

    Well-Known Member

    Nov 4, 2013
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    1,653
    Yes most DC rated relays and contactors will handle AC switching without issie.
     
  5. witailhntr

    Thread Starter New Member

    Aug 2, 2016
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    So if a 200 amp dc relay was used for a 70 amp ac contact do you feel this would be adequate? Thank you for your assistance and input.
     
  6. witailhntr

    Thread Starter New Member

    Aug 2, 2016
    4
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    So if a 200 amp dc relay was used for a 70 amp ac contact do you feel this would be adequate? Thank you for your assistance and input.
     
  7. witailhntr

    Thread Starter New Member

    Aug 2, 2016
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    0
    Thank you
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I would say so with some certainty.
    Max.
     
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