Suppressor Help

Discussion in 'General Electronics Chat' started by GARYN, Oct 22, 2009.

  1. GARYN

    Thread Starter Member

    Sep 4, 2009
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    Hello, I am an Engineer with basic electronic knowledge.
    Today i was disconnecting a faulty break coil (24VDC) on the end of a motor drive, accross the terminals was a RC suppressor. This was stright forward stuff but there was an area of confusion i would like your electronic expertise to clear up.
    I always thought RC suppressors were for AC only, Diode suppressors for DC and Varistor for both.
    Am I correct and the wrong suppressor is fitted or am i totally wrong?
    Thanks in advance for your replies.
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    Putting a rectifier across a DC relay coil slows the release so much that the contacts have a tendency to weld. Putting a Zener (Transorb) across still clamps the spike, but dissipates the coil energy faster (because the forward drop is so much higher than a simple diode) getting the relay armature moving faster, minimizing the contact welding problem. An RC snubber consisting of a lowΩ resistor in series with a DC blocking Capacitor is yet another way to dissipate the coil energy fast but hold the voltage to the coil current times the resistance.
     
  3. GARYN

    Thread Starter Member

    Sep 4, 2009
    47
    0
    Thanks for the info...
    But is a RC suppressor for AC only,
    And a Diode Suppressor for DC only.
    If this is the case can fitting the wrong one by mistake cause a problem.

    Thanks
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    No, an RC snubber is frequently used on DC relays powered with DC! It is actually better for the relay than a diode snubber, and equivalent to a Transorb.
     
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