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 Topic Title: Transformer Impedance Test & X/R Ratio Topic Summary: Created On: 25 July 2013 09:14 AM Status: Read Only Linear : Threading : Single : Branch
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 25 July 2013 09:14 AM jackdaniel Posts: 69 Joined: 29 November 2012 So guys, please help me to verify my calculation, From the short circuit Test of 4 kVA, 400/200 V, 50 Hz, 3-phase transformer has the following test data SC test: 20V, 10A, 100W Impedance % = (20/400) *100 = 5% Z= V/I = 20/10 = 2 Ohm R = P/3*I*1 = 100/(3*10*10) = 0.333 Ohm X = SQRT(Z2 - R2) = 1.972 Ohm So X/R ratio of the transformer is 1.972/0.333 = 5.922. is it correct? 25 July 2013 10:01 PM JonathanHill Posts: 225 Joined: 09 September 2002 I may be getting a bit rusty, my recollection for sc testing is to short-circuit the secondary (assume the 200V windings) and then raise the voltage until full load current flows in the primary. I get the primary FLC to be 5.797A which differs from your value. So unless my methodology is wrong, you can't deduce the impedance or X/R ratio from these test results. Looking forward to hearing from others. ------------------------- Jonno 28 July 2013 04:12 PM jackdaniel Posts: 69 Joined: 29 November 2012 Originally posted by: JonathanHill I may be getting a bit rusty, my recollection for sc testing is to short-circuit the secondary (assume the 200V windings) and then raise the voltage until full load current flows in the primary. I get the primary FLC to be 5.797A which differs from your value. So unless my methodology is wrong, you can't deduce the impedance or X/R ratio from these test results. Looking forward to hearing from others. John, Act I pick randomly the value, my objective is to determine the X/R value from the test. 29 July 2013 12:01 AM JonathanHill Posts: 225 Joined: 09 September 2002 Apart from the SC issue and values, I think your approach was OK, but would appreciate a sanity check from others. ------------------------- Jonno 11 August 2013 06:40 PM sreeraasi94 Posts: 5 Joined: 11 August 2013 Correct!
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