Effect of "Oversizing" an MOV

Discussion in 'General Electronics Chat' started by Rustifer, Dec 15, 2009.

  1. Rustifer

    Thread Starter New Member

    Dec 15, 2009
    4
    0
    :)Greetings to all on the GREAT forum. I'm new here and have little experience with electronics. I have a PLC w/relay outputs. One of these outputs will operate an external relay (24DC coil)that will then cycle a pull solenoid (24VDC-35 Ohm). I want to suppress the arcs in the external relay w/a mov as I've read from searching this fine forum.
    Question is: What is the effect of using a higher capacity mov than a perfectly sized one ? Just slower to react ? And can/should I use one also to protect the contacts in the PLC's relay too ?
    Thank you for your consideration,
    Rustifer
     
  2. Duane P Wetick

    Active Member

    Apr 23, 2009
    408
    19
    For DC coils, a free-wheeling diode across the coil will suppress the inductive kick. Personally, I like RC snubbers (0.1mf/ 100 ohm) for contact protection; cheap and reliable and available for 460 VAC circuits too. You can use MOV's in combination with other devices also, and you may find that it is needed.

    Regards, DPW [ Always remember that you are not going to live forever.]
     
    Last edited: Dec 15, 2009
  3. Rustifer

    Thread Starter New Member

    Dec 15, 2009
    4
    0
    Thank you very much DPW !
    I just tried the r & c and it looks to be excellent.
    I don't have a scope but the *contact lightening* is nearly non-existant now !

    THANKS again,
    Rustifer
     
    Last edited: Dec 15, 2009
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