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  1. #1
    Junior Member Tran_Lap's Avatar
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    Default 51 & 49 function relay

    Hi all

    New to the forum, can everyone help me to explain the difference between 51 and 49 function relay incase motor protection.

    Thank you
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  2. #2
    Senior Member mrloy99's Avatar
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    Default Re: 51 & 49 function relay

    Quote Originally Posted by Tran_Lap View Post
    Hi all

    New to the forum, can everyone help me to explain the difference between 51 and 49 function relay incase motor protection.

    Thank you
    tooo vague

  3. #3
    Senior Member DanBrown's Avatar
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    Exclamation Re: 51 & 49 function relay

    What do you mean exactly 51 & 49??, is this on the contactor overload??

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    Super Moderator Lenny's Avatar
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    Default Re: 51 & 49 function relay

    Hey.

    With regard to motor protection there are a number of different relays that have different jobs.

    Function 49 is overload protection
    Function 51 is locked rotor protection.

    There are lots of others - 50 = phase fault protection
    50N = earth fault protection
    50 + 51N = Time overcurrent with thermal in built.

    You can also get harmonic protection etc etc

    Hope this helps

    Cheers
    Last edited by Lenny; 12-01-2009 at 06:56 PM.

  5. #5
    Junior Member Tran_Lap's Avatar
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    Default Re: 51 & 49 function relay

    my understanding 51 using for overcurrent protection, but the reason of overcurrent is overload, 49 is thermal relay and the reason is overload too. So, can I use one of them for overload protection? when do I use both ?

    thank you
    Last edited by Tran_Lap; 13-01-2009 at 04:18 AM.
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