课程名称︰电力工程导论
课程性质︰电机系选修
课程教师︰许源裕
开课学院：电机资讯学院
开课系所︰电机工程学系
考试日期（年月日）︰2018/01/08
考试时限（分钟）：120(?)
试题 :
1. Find the magnetizing inductance referred to the high voltage side of 200
turns /20 turns single phase transformer with a core with A1 = 20cm^2, A2 = 50
cm^2, A3 = 20cm^2, A4 = 50cm^2, and μR = 1000, as shown below. (15%)
https://i.imgur.com/s31DiFt.jpg
2. Three identical ideal single phase transformers, each with a turn ratio of
1:100, are connected as a three phase transformer, as shown in the figure. Let
n and n'be the neutrals for the low voltage side and highi voltage side,
respectively. Assume that v_a'n'(t), v_b'n'(t), v_c'n'(t) are balanced negativ
e
sequence three phase voltages with v_a'n'(t) = 12700√2‧cos377t (V). Find
v_an(t), v_bn(t), v_cn(t). (15%)
https://i.imgur.com/qOCdRMG.jpg
3. A three phase load of 30MW, 22KV(line-to-line), PF = 0.9 lagging is
supplied power from a three phase transformer T which is composed of three
single-phase transformers each rated 89KV/21KV, 10MVA with leakage reactance
of 0.1pu. The resistances and exciting current of the transformer can be
neglected. Select a base of 36MVA(3ψ) and 161KV(line-to-line) at the high
voltage side of the transformer.
(a) Find the per unit leakage reactance of the three phase transformer T. (10%
)
(b) Find the per unit voltages for |V_L| and |V_S|. (10%)
https://i.imgur.com/cNWt1f6.jpg
4. Find the frequency of the armature currents when a 4-ploe synchronous
generator rotates at a speed of 1500rpm (revolutions per minute). (10%)
5. A salient pole synchronous generator delievers a complex power of S_G = 0.8
∠20。 at a terminal voltage of Va = 1.05∠0。. Assume that Xd = 1.2, Xq = 0.8
, and r = 0. Find the open-circuit voltage Ea. (20%)
6. Sketch a phasor diagram and calculate the open circuit voltage |Ea| for a
round-rotor synchronous generator which delivers P_G = 0.8 at 0.9 PF leading
to a bus with voltage |Va| = 1.03. Assume that r = 0 and X_S = 0.8. (20%)