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 Topic Title: Current in a 2 phase transformer Topic Summary: how do I calculate the current? Created On: 25 September 2013 09:31 AM Status: Read Only Linear : Threading : Single : Branch
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 25 September 2013 09:31 AM anoor Posts: 2 Joined: 12 July 2010 I am a graduate engineer and have been set a small task to work out the current (primary side) in a 2 phase 30kVA 415:650 tranformer. The 2 phases have been utlized from a 3 phase source and are hence 120degrees out of phase. I understand had it been a 3 phase 30kVA transformer I could calculate my current by 30kVA / 415 / route*3 = 42A. If it was a single phase then simply 30kVA / 415 = 73A. However if i am only using 2 phases from a 3 phase source yet still need to produce 30kVA of power, how do a calculate the line current? Thanks in advance. 25 September 2013 07:17 PM AdrianWint Posts: 304 Joined: 25 May 2006 Hint .... think about what the transformer actually sees ....... does it really see two phases .... or is the transformer really a single phase transformer that just happens to find itself connected to a 415V source? How many sinewaves does it see? What about the current in each of the supply legs? It is the same? Adrian 25 September 2013 10:30 PM anoor Posts: 2 Joined: 12 July 2010 I would consider it a single phase with a 415V input yet at the same time it sees two sine waves phase shifted? As with a balance 3 phased load i would expect the current magnitude in each leg to be the same? 25 September 2013 11:31 PM alancapon Posts: 6125 Joined: 27 December 2005 Originally posted by: anoor I would consider it a single phase with a 415V input yet at the same time it sees two sine waves phase shifted . . . Does it really? Draw two sine waves, one shifted by 120°, then draw the two added together. It sounds like you will be surprised by the answer. . . Regards, Alan.
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