[開課學院]: 資電學院
[開課系所]: 電機系
[課程名稱]: 電機機械(一)
[老師名稱]: 張正泓 老師
[開課學期]: 98-1
[類型]: 98-1期中考2
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[1]What are the reasons that the power source is just connect to the high
voltage sides of the transformers under testing ?
[2]A 5 kVA, 220/110 V,50 Hz transformer is connected to 220 V ,60 Hz power.
What will happen?
[3]What does the terminology , %IZ , mean ?
[4]A magnetic circuit consists of two parts .Length L1 ,L2 ,and cross section
areas A1 and A2 .If A1 = 25 cm^2 = 2A2 and L1 = 25 cm = 0.5L2 . Use the
Forelich equation B = aH/(b + H) to find the core flux . Assume a = 1.5 T,
b = 100 A/m and MMF = 1000 At.
[5]Two transformers,each rate 750 kVA,23000/230 V , are connected iv V
connection.
(a)Sketch the wiring and phasor diagrams
(b)Find the maximum capacity this system can supply.
(c)A 1000 kVA , 230 V , 0.8 lagging power factor , three-phase , delta-
connected load is connected to the system . Find the line current on high-
voltage side.
[6]A single-phase , 50 kVA , 3000/300 V two winding transformer is connected
as an autotransformer to supply a rated load of 3300 V. The power source is
3000V.
(a)Draw the schematic wiring diagram . Mark all the voltage and currents.
(b)Find the capacity of the autotransformer.
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