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4-Assignment4_Solution

# 4-Assignment4_Solution - ELECTRICAL ENGINEERING DEPARTMENT...

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ELECTRICAL ENGINEERING DEPARTMENT CALIFORNIA POLYTECHNIC STATE UNIVERSITY EE 255 Assignment #4 P roblem #1 A 100-KVA, 11000/2200-V, 60-Hz single-phase transformer has the following equivalent circuit parameters, referred to low-voltage side: , 1440 , 4950 , 49 . 2 , 531 . 0 = = = = m c eq eq X R X R The transformer is supplying at 2200-V rated load at a power factor of 0.8 lagging. Use the approximate circuit to determine: 1. The voltage regulation of the transformer, 2. The efficiency of the transformer. 1 I - + 1 V 531 0 . - ° = + KV V 0 2 2 2 . 49 2 . j 1440 j ' 2 I ' 1 E 4950 1) Voltage Regulation: A I 87 36 45 45 87 36 2200 10 100 2 2 . . . * - = ° - = V j V ° = + ° - + ° = 9 1 5 2288 49 2 531 0 87 36 45 45 0 2200 1 . . ) . . ( . . % . * . * 02 4 100 2200 2200 5 2288 100 2 2 1 = - = - = V V V VR 2) Efficiency: KW P Cu 1 1 531 0 45 45 2 . . * ) . ( = = KW P Core 06 1 4950 5 2288 2 . ) . ( = = KW pf S P out 80 8 0 100 = = = . * * % . * . . * 37 97 100 06 1 1 1 80 80 100 = + + = + + = Core Cu out out P P P P η Problem #2

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A 100-KVA, 60-Hz, 12000/240-V single-phase transformer is tested to obtain the equivalent circuit parameters using a short-circuit test. The voltage applied to the 12000-V side is 600 V with a short-circuit current equal to the rated current and short-circuit power of 1200 W. a. Find . and eq eq X R b. Assume that the transformer supplies a load of 100 KVA at 240 V and 0.95 PF lagging on the secondary side. Determine the voltage required at the primary side and the power factor. Short-circuit Test: V V sc 600 = W P sc 1200 = A I sc 3 8 12000 10 100 3 . * = = a) R eq and X eq : = = = 28 17 3 8 1200 2 2 . ) . ( sc sc eq I P R (HVS) = = = 29 72 3 8 600 . ) . ( sc sc eq I V Z (HVS) = - = 19 70 28 17 29 72 2 2 . ) . ( ) . ( eq X (HVS) b) Supply voltage and power factor: Load: 100 MVA, 240 V, 0.95 pf lagging 1 I - + 1 V 28 17 .
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4-Assignment4_Solution - ELECTRICAL ENGINEERING DEPARTMENT...

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