Definition of Ir and In in MCCB

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Truong Cong Le Participant Join Date: Apr 2008 Posts: 3	Definition of Ir and In in MCCB 07/27/2010 4:10 AM
	Please, give to know the differences between Ir and In in MCCB according to IEC recommendation 974-2. Thank you in advance
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Definition of Ir and In in MCCB 07/27/2010 5:24 AM
	→ British Standard 7671. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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kvsridhar Guru Join Date: Sep 2009 Location: Temporarily at Ashburn, VA Posts: 2744 Good Answers: 164	#2 Re: Definition of Ir and In in MCCB 07/27/2010 7:33 AM
	Please see this comment from JRaef on another thread: http://cr4.globalspec.com/comment/561110/Re-What-is-the-Ith-Ir-at-MCCB-stand-for Extract below for ready reference. Voltage Ue = Rated operational voltage Ui = Rated insulation voltage Uimp = Rated impulse withstand voltage Current In = Rated current Ith = Conventional free –air thermal current Ithe = Conventional enclosed thermal current Short -Circuit Icm = Rated short circuit making capacity Icu = Rated ultimate short circuit breaking capacity Ics = Rated service short circuit breaking capacity Icw = Rated short time withstand current Trip unit Ir = Adjustable overload setting current 1.05xIr = Conventional non –tripping current 1.30xIr = Conventional tripping current Isd = Short time delay tripping setting current Ii = Instantaneous tripping setting current i am curious. Since you mention IEC 60947-2, why did you need to ask this at all ? __________________ Nothing worthwhile can ever be taught, it can only be learnt.
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#3 Re: Definition of Ir and In in MCCB 04/28/2020 2:43 AM
	Is there a prize for getting it right? __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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vijaymail_electrical Commentator Join Date: Jan 2011 Location: India Posts: 98 Good Answers: 2	#4 Re: Definition of Ir and In in MCCB 07/23/2020 9:30 AM
	Ir: Rated current which is selected based on load current and protection settings. In: Rated current of MCCB or frame size. Ex: 160A MCCB with 100A TMD protection. Means 160A frame size of MCCB (In) and it has protection function for Ir:100A where you can either set the protection from 0.8..1.2xIr or fixed (i.e 100A) __________________ You don't understand anything until you learn it more than one way.
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