Synchronizing of 3-Phase Alternators

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Anonymous Poster #1	Synchronizing of 3-Phase Alternators 04/09/2014 12:28 AM
	Hi, If in a three phase system, one three phase alternator is already synchronized to three phase bus, then - to synchronize another three phase alternator - 1. " If the incoming alternator is running faster, then its voltage star R' Y' B' will appear to rotate anticlockwise with respect to the bus bar voltage star RYB at a speed corresponding to the difference between their frequencies." Why anticlockwise? I think it should be clockwise. 2. " Voltage across L1 is RR' and is seen to be increasing from zero. That across L2 is YB' which is decreasing, having just passed through its maximum. That across L3 is BY' is increasing and approaching maximum." How can this be justified? Regs,
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lyn Guru Join Date: Oct 2008 Posts: 42355 Good Answers: 1693	#1 Re: synchronizing of 3-phase alternators 04/09/2014 12:42 AM
	Is this multiple choice or essay? Is it an interview question, or do you work for a puzzle company? Or, are you just doing your homework? Where have you looked so far?
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SolarEagle Guru Join Date: Mar 2007 Location: by the beach in Florida Posts: 33392 Good Answers: 1817	#2 Re: synchronizing of 3-phase alternators 04/09/2014 12:53 AM
	It sounds like you are using a synchronoscope... A Synchronoscope is capable of rotating in both directions. The rate of rotation of the pointer indicates the amount of frequency difference between the Alternators. The direction of rotation indicates whether incoming Alternator frequency is higher or lower than the existing Alternator. The TPST switch is closed to synchronise the incoming Alternator when the pointer faces the top thick line marking. http://faculty.sau.edu.sa/filedownload/doc-2-pdf-335cd1b90bfa4ee70b39d08a4ae0cf2d-original.pdf __________________ All living things seek to control their own destiny....this is the purpose of life
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The.Tinkerer Guru Join Date: Apr 2012 Posts: 732 Good Answers: 17	#3 Re: Synchronizing of 3-Phase Alternators 04/09/2014 10:19 AM
	1. It would depend on the reference. If the "alternator" is referenced to the bus and is overspeed vs. if the bus is referenced to the overspeed "alternator". 2. This sounds like a homework problem. You should then reference the CR4 guidelines. __________________ common knowledge...less common than common sense
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RAMConsult Guru Join Date: May 2007 Location: NYC metropolitan area. Posts: 3230 Good Answers: 444	#4 Re: Synchronizing of 3-Phase Alternators 04/09/2014 12:43 PM
	Probably an interview question, and one that only an engineer experienced in this sort of thing could answer correctly. Since I'm averse to giving away these type of answers I'll just answer the question with another one, why do you think it should be clockwise? Second question, there's an error in it, L1 is not RR', it is either RY' or RB', and the answer depends on which it is. Can you tell us what is being described in both cases, please justify your answers. __________________ “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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