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Diode Surge Suppressors for Fuji Contactors

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  • Diode Surge Suppressors for Fuji Contactors

    Why are there only varistors and RC suppressors available for the Fuji contactors? It would be nice to have a diode option like the WEG contactors. The varistors do not offer enough protection for transistor outputs. There is even a note on the specifications PDF that recommends using diodes. It would be much easier if there was a diode packaged like the other suppressors, which bolt directly to the coil terminals.


  • #2
    Originally posted by ericn View Post
    It would be much easier if there was a diode packaged like the other suppressors, which bolt directly to the coil terminals.
    And the diode being closer to the coil minimizes the length of wire that would have to carry the reverse emf spike - which effectively would be a noise-radiating antenna.

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    • #3
      I once read somewhere that a simple diode reduces the life of contactors, by delaying opening causing more arcing in high current application. While I don't remember where I read it, Google will show you lots of examples that go into more detail. As it is public I'll just quote Wikipedia here:
      "When the inductive load is a relay, the flyback diode can noticeably delay the release of the relay by keeping the coil current flowing longer. A resistor in series with the diode will make the circulating current decay faster at the drawback of an increased reverse voltage. A zener diode in series but with reverse polarity with regard to the flyback diode has the same properties, albeit with a fixed reverse voltage increase. Both the transistor voltages and the resistor or zener diode power ratings should be checked in this case."

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      • #4
        Thanks for the post. I forwarded your question to the Product Manager for consideration with future releases.
        If you have an urgent issue, please contact AutomationDirect's Technical Support team at 1(800) 633-0405 or (770) 844-4200. Thank you

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