Power system operation

consider the circuit of Fig. 2. l 7(a). Let X = 1.5 Q. The source voltage
is a constant 100 40° V. Calculate and plot VSNR (both RMS values)(y-axis) vs P (x-axis), ifthe
load power varies in a range from 0 to 1 kW at the following 3 power factors: 1, 0.9 (lagging), and
0.9 (leading). To solve the problem, express P as a function ofthe RMS values of V, and the current
I, and the necessary phase. Note that V3 is constant. Select P = 100 W, 500 W, and 1000 W. Find
the necessary current to satisfy this equation for all 3 power factors. Then use KVL to find what
the phasor for vu(t) (at the calculated 1) is and then calculate the RMS value Va. Note that you
should have 3 total curves, 1 for each power factor.
In class, an example was given using Fig. 2-12(a) and subsequently Fig. 2.l3(a) to calculate per
unit values of the per-phase voltage, the load impedance, the load current, and the load real and
reactive powers. In the class example, the line to line base voltage was given as 208 V (RMS) and
the base value of the three-phase power was given as 5400 W.
a Calculate the per-unit values of the parameters above if the base three-phase power is
changed from 5400 W to 3600 W.
b. Repeat this problem but now the line to line base voltage is 240 V (RMS) and the base
three-phase power is 5400 W.
c. Repeat the problem again with line to line base voltage as 240 V and the base three-
phase power as 3600 W.
Consider the toroid shown in Fig. 2-21 (a). The current is 3 A, and the number of turns around coil
is 25. The inner diameter is 5 cm, and the outer diameter is 5.5 cm.
a. Calculate the magnetic field intensity H very close to the inside diameter (don‘t include
the outer diameter in the calculation).
b. Calculate the magnetic field intensity H very close to the outside diameter (don’t
include the inner diameter in the calculation).
c. Compare the results with those obtained in class where the mean diameter was used.