Recirculating current

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watdefak Associate Join Date: Dec 2005 Posts: 27	Recirculating current 10/10/2007 10:11 PM
	What exactly causes Re-Circulating Current and what are the effects it causes ? __________________ When it comes to engineering, what we call ourselves is not supposed to matter. The only thing that matters is the knowledge we attain and the respect we give each other.
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Anonymous Poster	#1 Re: Re circulating current 10/11/2007 4:55 AM
	http://en.wikipedia.org/wiki/Eddy_current
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solaaderinwale Active Contributor Join Date: Sep 2007 Posts: 21 Good Answers: 1	#2 Re: Re circulating current 10/11/2007 8:01 AM
	It is expedient to have all parallel-running generators carry their proportionate share of total reactive load. To do this, they must each have the same generated e.m.f. - which is a function of field excitation. However, where two generators are running under unequal excitation , the generated e.m.f.s would not be the same. This difference in voltage, E₁- E₂, sets up a circulating (or cross) current, I_c which is equal to this voltage difference divided by the total impedance of the two machines, i.e. I_c= (E₁ - E₂)/2Z The main effect of the circulating current is the increase in kVAr output of the generator with higher excitation and reduction in that of the other. The additional loading, and the subsequent heating effects, limit the active power output of the former. There is also the lowering of the busbar voltage. Adjustment of the machines' excitation will however correct this. __________________ One does not need a mirror to look at what one is wearing on the wrist
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Samak Commentator Join Date: Sep 2007 Location: Alexandria, Egypt Posts: 86 Good Answers: 1	#4 In reply to #2 Re: Re circulating current 10/11/2007 5:18 PM
	This is a very good answer.
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charsley99 Guru Join Date: Oct 2006 Location: New Jersey U.S.A. Posts: 1114 Good Answers: 38	#3 Re: Re circulating current 10/11/2007 8:06 AM
	As the above link points out they are induced voltages or currents. Even with a VFD or SMC, stopping a large machine with a heavy load can sometimes cause the equipment to drop out on overvoltage sensing. Think of a generator in your car. __________________ The last fight was my fault. My wife asked "What's on the TV?" I said "Dust!"
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HUX Power-User Join Date: Jan 2007 Location: UK S.Northants Posts: 485 Good Answers: 19	#5 Re: Recirculating current 10/12/2007 5:35 AM
	does current flowing in earth loops count?
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Anonymous Poster	#6 In reply to #5 Re: Recirculating current 07/07/2010 2:38 PM
	Circulating current also flows due to the different coil pitches of alternator running in parallel and having their neutrals interconnected. Is there any technical writeup for that current on web that how it may be prevented e.g choke coil method and others ?
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Anonymous Poster (2); charsley99 (1); HUX (1); Samak (1); solaaderinwale (1)

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