Exam 1_04_Sp-11_Solution

# Exam 1_04_Sp-11_Solution - ELECTRICAL ENGINEERING...

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ELECTRICAL ENGINEERING DEPARTMENT EE 255-04 MIDTERM May 2nd, 2011 I have neither given nor received unauthorized assistance during this test. Name (Print)_______________________________ Signature:__________________________ P roblem #1 (10 P oints ) A 132-KVA, 11,000:2,200-V, 60-Hz single-phase transformer has the following circuit parameters: Primary (HVS) Secondary (LVS) R1 = 6.1 R2 = 0. 3 X1 = 31.2 X2 = 1.2 Rc = 57,300 Xm=124,000 Rc and Xm are HVS parameters. The transformer is supplying at 2,200-V the rated load at 0.95 power factor lagging. Use the approximate circuit to determine: 1. The voltage regulation of the transformer, 2. The all-day efficiency of the transformer for the following load cycle: 12 hours full-load and 0.95 power factor lagging 4 hours 50% full-load and 0.95 power factor lagging. 1 I - + 1 V 10 - + ' 2 V 50 j m jX ' 2 I m I = + = = + = 2 61 5 2 1 2 31 6 13 2200 11000 3 0 1 6 2 2 . ) ( * . . . . . eq eq X R V V ° = 0 11000 2 ' A I ° - = ° - = 2 18 12 2 18 11000 132000 2 . . ' V j jX R I V V eq eq ° = + ° - + ° = + + = 25 3 11403 2 61 6 13 2 18 12 0 11000 2 2 1 . ) . . ( .

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