Locked Rotor Current

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veronica Member Join Date: Sep 2008 Posts: 6	Locked Rotor Current 10/10/2008 1:14 AM
	Hello, Can anyone help me to find out the rated current/locked rotor current & load factor of a 15KW motor which is connected to 415V ac.Estimated full load current & maximum demand are 26Amps.Load diversification=.06.Thanks 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: to find locked rotor current 10/10/2008 5:11 AM
	Apply a multimeter between phase connections of a single winding, set to ohms, or possibly milliohms. Divide the resistance figure into the supply voltage. Bingo. __________________ "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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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	#2 In reply to #1 Re: to find locked rotor current 10/10/2008 7:22 AM
	A rule-of thumb: the locked-rotor current is 5 times the full-load current for direct-on-line starting. __________________ "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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veronica Member Join Date: Sep 2008 Posts: 6	#3 In reply to #2 Re: to find locked rotor current 10/10/2008 7:27 AM
	Thank you.It was helpful.
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Anonymous Poster	#4 Re: Locked Rotor Current 10/11/2008 7:22 AM
	The NEMA Standard MG- 1 has recommended the maximum locked rotor current of single-speed three phase motors for the various rotor designs B, C, and D, for various recommended torque values. These have been derived for a 415 V a.c. system and are shown as following: 20 hp (15KW) ------------ 178A (locked rotor current) Also typical rated power factor for this rating is 0.86, as you know power factor in motor starting duty is very low. -------------------------------------- Creative thinking is enjoyable, Then think about your surrounding things and other thought products.
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nesubra Guru Join Date: Nov 2006 Posts: 729 Good Answers: 2	#5 Re: Locked Rotor Current 10/11/2008 1:38 PM
	LRC is normally 6 times rated current+-20%.Usually it is +tolerance.If full load current is 26A then LRC is between 156 Amps-187.2 amps.It is independent of other parameters but depends upon the motor design .Duration depends upon the load inertia. __________________ To avoid crticism do nothing,say nothing,be nothing
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Anonymous Poster (1); nesubra (1); PWSlack (2); veronica (1)

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