Relay current

Discussion in 'General Electronics Chat' started by Dritech, Dec 3, 2013.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Hi,

    If a relay is rated to have a Nominal switching capacity of 16A 277V AC, what will be the maximum current if 12VDC are switched instead?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
    2,369
    The ratings for contacts, both AC and DC are usually stated in both Resistive and inductive, for DC the current would typically be more for the lower DC voltage range, but less at the equivalent rated AC voltage value.,
    You really need to consult the manuf. spec if they are available.
    Do you have a part number in mind?
    Max.
     
  3. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    After seeing the datasheet the proper answer is.. Its not rated for DC at all and thus should not be used for switching DC..
     
  5. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Hi, What makes a relay good for switching AC but not DC?
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
    2,369
    DC, especially an inductive load requires rapid release action and adequate contact area.
    The relay you show, is not only recommended for AC but a resistive load, which is not so demanding on the contact composition.
    Max.
     
    Dritech likes this.
  7. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,509
    2,369
    That would be a better choice, it is similar to automotive relays, which incidentally you can pick up fairly cheap, especially at a recycler.
    If the motor has other control such as DC speed controller, it is best to make sure is low speed or stopped before operating the relay if possible.
    Max.
     
  9. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    756
    5
    Thanks for the info.
     
Loading...