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**Lenny** · 12-01-2009

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

12-01-2009	#4 (permalink)
Lenny Moderator Join Date: Dec 2008 Location: South Wales Posts: 3,304 Thanks: 143 Thanked 539 Times in 472 Posts	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 07:56 PM..