Chapter 3: 12MCQ (page 87)
The per-unit quantity is always dimensionless.
(a) True
(b) False
Therefore, the correct option is (a) True
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Consider the equivalent circuit of figurein the text. After neglecting the winding resistances and exciting current, could becomes negative, even though the leakage reactance are always positive.
(a) Yes
(b) No
A low value of transformer leakage reactance is desired to minimize the voltage drop, but a high value is desired to limit the fault current, thereby leading to a compromise in the design specification.
(a) True
(b) False
In developing per-unit circuits of systems such as the one shown in Figure 3.10, When moving across a transformer, the voltage base is changed in proportion to the transformer voltage ratings.
(a) True (b) False
A three-phase transformer is rated ,. The Y-equivalent short-circuit impedance, considered equal to the leakage reactance, measured on the low-voltage side is.Compute the per-unit reactance of the transformer. In a system in which the base on the high-voltage side of the transformer is,, what value of the per-unit reactance should be used to represent this transformer?
Figure 3.32 shows the one line diagram of a three-phase power system. By selecting a common base ofandon the generator side, draw an impedance diagram showing all impedances including the load impedance in per-unit. The data are given as follows:
G:
T1:
T2:
T3: localid="1655975246589"
T4:
M:
Lines 1 and 2 have series reactane ofand,respectively. At bus 4, the three-phase load absorbsatandpower factor lagging.
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