railway power transmission

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ABHIJITH Participant Join Date: Dec 2008 Posts: 3	railway power transmission 12/20/2008 9:46 AM
	we know that electric train engine is a dc motor.the question is weather the power is transmitted as dc or ac?
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Bricktop Guru Join Date: Mar 2008 Location: The People's Republic of Massachusetts Posts: 1946 Good Answers: 73	#1 Re: railway power transmission 12/20/2008 12:52 PM
	Electric trains can be ether AC or DC. I'm no expert, but I believe if the power transmission is DC, the the train has a DC motor, and vice versa. __________________ I go into every human encounter expecting to be framed for a crime I didn't commit. Dilbert, 2013
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Sparkchaser Power-User Join Date: Aug 2006 Location: Adirondacks of NYS Posts: 136 Good Answers: 7	#4 In reply to #1 Re: railway power transmission 12/21/2008 10:18 AM
	Two cannibals are have lunch, one says to the otther "My your husband makes a great soup...." "Yes" says the other, "But I think I going to miss him..." BRICKTOP STARTED IT!!!! __________________ If I hear hoofbeats, why don't I ever think a Zebra might be around?
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GordieGii Power-User Join Date: Nov 2006 Location: Ontario, Canada Posts: 146 Good Answers: 1	#2 Re: railway power transmission 12/20/2008 7:47 PM
	Wouldn't it be faster to just look at the wall adapter? __________________ Logic is the art of going wrong with confidence. -- Morris Kline
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leveles Guru Join Date: Jan 2008 Posts: 1753 Good Answers: 59	#3 Re: railway power transmission 12/21/2008 12:01 AM
	No. The engine's motor can be DC or variable AC. The control of the second is far more complicated, but advantageous power control vise. The normal feed to the engines is AC, but old systems exist with all DC controls. Just check out the trains in Swiss mountains. Old and new mix.
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otha Power-User Join Date: Oct 2008 Location: Meherrin Virginia Posts: 319 Good Answers: 6	#5 Re: railway power transmission 12/21/2008 11:20 AM
	At one point the Bethlehem Steel plant in Maryland had 25 cycle generators for this purpose. They also had frequency convertors to convert normal line frequency from 60 to 25 cycle. The need for 25 cycle power was gradually diminished to the point that none was required. I am fairly sure that the main requirement for the 25 cycle was for the trains. I could be wrong because we had another plant in Maine that had 40 cycle machines and didn't have extensive rail capability. The interesting thing about the Beth steel unit was, reserve power became so lucrative an asset that Beth brought this unit that was initially syncronized in the mid 20's back on line about 15 years ago back feeding through the ferq convertors to generate 60 cycle for reserve power. __________________ If you fail to follow through, you will fail.
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Haajee Guru Join Date: Feb 2006 Posts: 1758 Good Answers: 6	#6 Re: railway power transmission 12/21/2008 8:10 PM
	Regards Overhead power to train is AC, Rectifid & Drive-Motors are Brush-less Motors Have a good day & happy X-Mas
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Chankley Power-User Join Date: Sep 2007 Location: South coast of England Posts: 411 Good Answers: 36	#7 Re: railway power transmission 12/22/2008 5:37 AM
	Most of the latest rolling stock uses ac motors with 3 phase variable frequency drive, however there are still many in service with dc motors.
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VMI1998 Commentator Join Date: Aug 2008 Location: Ohio Posts: 96 Good Answers: 3	#8 Re: railway power transmission 12/22/2008 10:49 AM
	I used to work for a company that provided power for light (passenger) rail. 3rd rail systems run on DC. Here's their link. __________________ I would rather be ashes than dust...
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Chankley Power-User Join Date: Sep 2007 Location: South coast of England Posts: 411 Good Answers: 36	#9 Re: railway power transmission 12/23/2008 4:37 AM
	I realise that my previous comment failed to answer the original question properly. I addressed the incorrect assumption that the motors are dc, when in fact they can be either ac or dc. The transmission system can be either ac or dc as well. Light rail systems are almost always about 750V dc with a few at 1500V dc. Almost all new long distance systems in Europe are 25kV 50Hz (or 15kV 16 2/3Hz in the Germanic countries). Some countries have a large amount of older electric railways running on dc, usually 1.5kV or 3kV overhead or 750V 3rd rail systems (or 4 rail for some underground lines where a separate return rail is used). In other parts of the world 50kV is used on long distance heavy haul lines and 11kV is used extensively on the east coast of the USA Due to the size of the old systems it is not economic to convert them to 25kV ac so there are many classes of train able to run on several different types of supply.
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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	#10 Re: railway power transmission 12/23/2008 11:50 AM
	The Eurostar trains that pass through the Channel Tunnel pick up current from one of three systems, depending upon where they are: 750VDC third rail or 25kVAC overhead in the UK, 25kVAC overhead in France and 1500VDC overhead in Belgium. Transfer from one system to another happens seamlessly, and while travelling at speed. "Horses for courses"? __________________ "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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Bricktop (1); Chankley (2); GordieGii (1); Haajee (1); leveles (1); otha (1); PWSlack (1); Sparkchaser (1); VMI1998 (1)

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