Overload Setting

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Anonymous Poster	Overload Setting 09/15/2010 1:06 AM
	May I know how to set overload setting for motor with DOL starter. example : motor rated current is 8.80 A. V 415. 2.91 kW. pf 0.85 so I assuming that will be what I need to set overload setting and how I choose to use overload setting . and how to select the mcb also.
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vinod tomar Active Contributor Join Date: Jun 2010 Posts: 15	#1 Re: Overload Setting 09/15/2010 2:11 AM
	You can easily select the switch gear and ratings form the catalog of any reputed (ABB, Siemens, L&T) switchgear manufactures. Also these information are available with motor manufactures.
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SHAMITHGAMBHIR1 Power-User Join Date: Feb 2010 Location: dubai,mangalore,bangalore..... Posts: 145 Good Answers: 8	#2 Re: Overload Setting 09/15/2010 2:29 AM
	based on the motor type olr setting= 115-125% motor flc mcb = 150-250% motor flc check out this link http://cr4.globalspec.com/thread/56416#comment586920 __________________ shamith gambhir, electrical engineer
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Tanuja Active Contributor Join Date: Sep 2010 Location: United Arab Emirates Posts: 12 Good Answers: 2	#3 Re: Overload Setting 09/15/2010 2:39 AM
	Its 3 phase so formula is: I = kW / ( √3 x pf x VLL ), in kA
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Tanuja Active Contributor Join Date: Sep 2010 Location: United Arab Emirates Posts: 12 Good Answers: 2	#4 Re: Overload Setting 09/15/2010 2:40 AM
	Run the motor/pump at full load and then tong the cables. then set the starter 10% above that.
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kvsridhar Guru Join Date: Sep 2009 Location: Temporarily at Ashburn, VA Posts: 2744 Good Answers: 164	#5 Re: Overload Setting 09/15/2010 3:46 AM
	In IEC countries, you need to set the relay at actual motor current, not higher. The relay already has a factor of 1.125 (1.05-1.2 range) built into the trip characteristic as per IEC 60947. If you set the relay higher, it will not protect the motor on overload. The back up MCB will also need to be set at fairly close to this value. If you can get a 'magnetic-only' MCB, which does not have a thermal element, it will be better. If you want Type 2 co-ordination, it needs more analysis. As Vinod Tomar says, most good manufacturers give the whole selection. You will be better off using their recommendation. __________________ 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	#6 Re: Overload Setting 08/29/2024 7:10 AM
	Assuming the abbreviation <...mcb...> means "miniature circuit breaker", the correct protocol may be found in many countries' electrical standards, such as BS7671 in the UK. Commonly, motor cables are protected by fuses instead. The relationship between overload setting for the motor and other protection for the cables is called "co-ordination", and forms the training of a qualified Electrician, who is there to design, select, install, test and certify as safe upon completion of the testing. If one is not to hand, then hire someone locally. __________________ "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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