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test1a - 3 A 20 KVA 440/220V 60 Hz single-phase transformer...

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Unformatted text preview: 3. A 20 KVA: 440/220V, 60 Hz., single-phase transformer has iron loss of 324 watts. A . A 3-phase, 300 KVA, 12,470/208 V, 60 Hz., Wye-Wye connected transformer fl I .. cl The line breaker capacities on the HV and LV side of the transformer.’ 5/ I v“. fli— .f\ [am Monday, February 26, 2001 EE 381 . ' Spring 2001 Test 1 . An iron ring has a cross-sectional area of 4 square centimeters. An air-gap of length 0.4 millimeters is cut across its section. The mean length of the iron is 100 centimeters. The ring is wound with a coil of 500 turns and carries a current of 1.2 amperes. If the total magnetic flux is 0.3 milliwebers, find the relative permeability of the iron and the energy stored in the air gap. Neglect fringing and leakage. uo=41t 10'7. , . A single-phase, 600 KVA, 11000/550 V,>6O Hz. transformer has an equivalent impedance referred to the HV side given as Zch = I. 8 + j ’i- 4 ohm Determine the percent regulation of the transformer when the transformer is supplying an inductive load with 450 KW and 262.5 KVAR at 550 volts. k” _ (put-.9 #4421): Vi -. w \JA ,the copper loss is found to be 100 watts when delivering half full load current. Determine the efficiency when delivering full load current at 0.8 power factor ' leading. Find also the KVA for maximum efficiency and the efficiency at this KVA if the power factor is 0.6 lagging. - 4. A small 2-winding transformer has its voltage and current ratings as shown. This translurmer is to be connected as a 120 V to 132.6 V Step-up autotransformer, a) Show the connection diagram indicating all dot terminals. . 125*: b) What is the tull load VA or the autotransformer? c)- What are the winding currents and V'Amdmm and V’Amducfiyc. Lu: “W 3M5. ‘2'“ I lll i supplies a department store. .The department store 3-phase load is 250 KVA at 0.8 . ' T— lagging and connected in delta. If the transformer is assumed ideal show the '_ (qr... following: if a) The diagram of connections --- showing the primary, secondary and the load. - L_.i l-\ TL .——- —L--_ ‘_ J 1.. A an U) Lite Pm. yuan» Luau uupCuafluu. 9!. 9/ [1" _ I. L‘L‘\) M -4 _ ‘I gug 435,13 ; I i I flan_ ' ' ”’2 :' ...
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