Contactor and Relay differences

This topic contains 6 replies, has 2 voices, and was last updated by  Pete Fosbender 1 year ago.

  • Author
    Posts
  • #7966

    Pete Fosbender
    Participant

    Hello Galco, I would like to know, what are the differences between Relays and Contactors?
    They seem to be the same thing.
    Pete


  • #7967
    John C
    John C
    Galco Representative

    Hello Pete, thanks for visiting our web forum today. I would be happy to help you with the differences.
    First of all they are basically the same thing, but there are also unique differences.
    Contactors are generally made for high power use in 3 phase applications, but are also available 2 pole for DC applications. Because of the high currents they are made to handle they usually have magnetic arc chamber to extinguish arcs in shortest possible time. They will also have the ability to mount auxiliary contacts for low power signalling to the control circuits.
    Relays are much more simple in nature, they just have a number of poles controlled by the coil to open or close them when energized. Relays don’t necessarily have auxiliary contacts but some types will have stackable contact blocks to be able to add poles if needed.
    Both are operated by a coil that is available in different voltage ratings, and both operate contacts to open or close when energized.
    Hope this helps
    Regards and Happy Thanksgiving
    John


  • #7968

    Pete Fosbender
    Participant

    Thanks John, this is very helpful, but have another question.
    So what kind of power are they rated for and what are the coil voltages?
    How do I know which type to use?


  • #7969
    John C
    John C
    Galco Representative

    These are great questions Pete.
    Ok well relays will generally be used to switch low power like 10volt, 24volt, 115volt AC or DC signals at less than 20amps of current.
    Contactors, on the other hand, are made to handle much higher currents and voltages. A small contactor might only be rated up 20 amps of current. Where a large contactor will do 10 times that or 200amps up to a thousand volts.
    To decide which to use, simply identify the number of poles needed for your application, the coil voltage needed (many different volts available for coils, 24Vdc minimum usually, and up to 480Vac) and then the maximum amount of amps to switch on and off.
    Better?


  • #7970

    Pete Fosbender
    Participant

    Yes John that is better, reason I’m asking is I have an old ABB DCS800 drive and it looks like the contactor went bad. 1 of the terminals is all discolored looking like it got really hot for a while and this thing hasn’t run in almost a year. Well now we need it running, can you guys help?


  • #7971
    John C
    John C
    Galco Representative

    Absolutely Pete.
    Do me a favor though, first gather the name plate data of the drive in question.
    We will need the whole part number ok?
    Then give us a call at 248-336-4591, this is Randy Barbret’s direct line. He is our ABB product manager and has many years of experience with ABB products. He will be able help you figure out what that contactor was and get a replacement ordered.
    Good luck and thanks again for asking Galco
    John


  • #7972

    Pete Fosbender
    Participant

    Very good, I will do just that.
    Thank you very much
    Pete


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