Use of AC operated relays

Discussion in 'General Electronics Chat' started by dermotx, Apr 27, 2014.

  1. dermotx

    Thread Starter New Member

    Apr 27, 2014
    2
    0
    Hi, I'm new to using AC operated relays. I want to use an AC powered relay to turn a single phase load ON and OFF. The coil of the relay is 230V AC 50 Hz and the load I want to turn on is up to 30A. I'm using a Finder DPDT 230VAC relay. (66.82.8.230.0000)
    I have two questions:

    1. Do I need to add flyback diodes like DC relays use. At the moment I'm just connecting the neutral and live across the coil and the relay is operating fine.

    2. Should I put an inline fuse to the relay coil. It only draws 15mA.

    Any help would be appreciated. Thanks

    Dermot
     
  2. profbuxton

    Member

    Feb 21, 2014
    233
    68
    Diodes should NOT be used on AC relays. If volt spikes are a problem you may use a suitably rated varistor or a resistor and capacitor in series across coil to act as a "snubber".
    A fuse is not strictly needed but may help protect wiring if coil goes shortcircuit.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,565
    2,379
    +1 on RC snubber.
    Max.
     
  4. #12

    Expert

    Nov 30, 2010
    16,343
    6,828
    1. Connecting it with what? A mechanical switch? A triac?

    2. I don't think so. More likely to cause nuisance failures than to protect anything.

    3. There are relays called, "contactors" that are SPST or DPST made for exactly this purpose. That is, assuming you don't need another circuit powered when there is no activation voltage on the coil. This is a, "Keep it simple" suggestion, but contactors are bulky compared to relays.
     
  5. dermotx

    Thread Starter New Member

    Apr 27, 2014
    2
    0
    Thanks guys for the quick and informative replies.

    Regards

    Dermot
     
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