Exam2Solutions-Spring09

Exam2Solutions-Spring09 - EEL 3211 Test 2 Mar 19 2009 Time...

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EEL 3211 Test 2 Mar. 19, 2009 Time limit: 50 minutes Show all work! 1. (20 Points) An ideal transformer has N 1 = 2000 and N 2 = 500. An impedance Z 2 is connected across winding 2. If V 1 = 1200 0 o V and I 1 = 5 0 o A find Z 2 . 2. (20 Points) A real transformer has N 1 = 2000 and N 2 = 500. The winding resistances are R 1 = 2.0 Ω and R 2 = 0.125 Ω. Leakage reactances are X 1 = 8.0 Ω and X 2 = 0.50 Ω . A resistive load of Z 2 = 12 Ω is connected across the secondary (side 2). If V 1 = 1200 0 o V, find the voltage regulation. Neglect the magnetizing reactance.

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Since 3. (20 Points) A transformer is rated at 15 MVA, 11.5 kV:69 kV. If the 11.5 kV winding is short-circuited, the rated current flows when the voltage applied to the other winding is 5.50 kV. The input power is 105.8 kW. Find R 1 and X 1 referred to the high-voltage winding. Short-circuit the 11.5 kV and neglect the shunt impedance (as done in class). The rated current for the 69 kV winding has magnitude: Then: Many of you choose to do the problem this way:
4. (20 Points) A transformer is rated at 15 MVA, 11.5 kV:69 kV. If the 11.5 kV is applied to the

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Exam2Solutions-Spring09 - EEL 3211 Test 2 Mar 19 2009 Time...

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