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Unformatted text preview: ¢ fig (5 \U\\D‘lvi EE 3410: Power Systems
Test #1 , \x September 29, 2004 NameEMC'P U/ 7 EBBEKT Solve 3 of 4 following numerical problems.
/ ~ roblem 1. (20p) The rotor of a power generator has length l = 3 [m] and diameter 2R = 1.5 [m]. " t is made of laminated iron of mass density p = 7.2 103[kg/m3]. Calculate energy needed for the
rotor acceleration to velocity of a) = 3600 [rev/min]. Calculate maximum power of the rotor. ****************************************************************** Problem 2. (20p) A substation bus with line—toground voltage RMS value E = 3.0 kV has the
shortcircuit power, per phase, SSC = 1.5 MVA. The reactanceto—resistance ratio at the bus is % Xs/RS = 55 = 3. Calculate the supply resistance RS and inductance L5. The supply voltage
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frequency 15f: 60 Hz. ****************************************************************** Problem 3. (20p) Calculate the active power of all elements in the circuit shown in Fig. 1, assuming that the supply voltage RMS value is U = 240 V. Verify the active power balance.
R2 L i Fig. 1
The circuit parameters are R2 = 0.5 Q, R1=1.SQ, wL1=1.5 Q, (0C1: 0.8 S, *************************r***************************************** ' Problem 4. (20p) Calculate how much energy in kWh is needed for heating 100 liters of water
C from temperature of 21°C degree to boiling temperature. Assume, that half of delivered energy is lost. ******************************************************************** Answer 8 of 10 following questions 9 Question 1. (5p) Explain, why transmission lines are built as threephase lines? § Question 2. (5p) Explain, why very high voltage has to be used for energy transmission? I»
g Question 3. (5p) Explain situations in which energy has to be transmitted by DC lines.  " ‘3 Question 4. (5p) Explain Oersted, Faraday and Maxwell contribution to electrical engineering. 1 it“ ,.
‘3’ ‘ ( Question 5. (5p) When and where in USA the ﬁrst AC line was built. “
it 5’ Question 6. (5p) What it is British Thermal Unit (Btu)?. '4
\‘KL: Question 7. (5p) How much energy is needed for vaporization of one liter of water? a. K) Question 8. (5p) Prove that instantaneous power of inductors is p(t) = u(t) z'(t). ‘C r115; Question 9. (5p) Explain physical meaning of the reactive power. 2' Question 10. (5p) Prove that power balance is not satisﬁed for the apparent power. a" Ceugcﬂo 115 (9/0 LAG Met—y EE 3410: Power Systems ' ‘P ,7
Test #2 November 1, 2004 '
5" ﬂ :3": x". Solve 3 of 4 following numerical problems. Problem 1. (20p) A resistiveinductive, 100 kW at 2.4 kV load with power factor it = 0.6, is
supplied a bus with the shortcircuit power SSC = 1.5 MVA and the reactancetoresistance ratio \0 XS/RS = is = 3. Calculate capacitance of the compensator that improves power factor to unity and
\ the distribution voltage, E, beforeand after compensation, if the load voltage RMS value U: 2.4
kV has to'be preserved. ****************************************************************** Problem 2. (20p) Calculate the force F exerted on a segment of the conductor 0 of a threephase
(3 line of the length [=1 meter and its direction, if the conductor 0 current is ID =  1000 A,
assuming that the distance between condactors d = 0.5 m. } 13:500A 1b=500A
f ; {M 69 ea .
=. A a b "I '. § (
J .' :14“. 1. Ic=1000A ‘ *********¥******************************************************** Trobiem 3. (20p) Hawing a ferromagnetic core with relative permeability ,u = 8000 and Bmax r
1.2 Wb/rnz, cross—section area A = 16 cm2 and the magnetic path length l = 60 cm, design an
up inductor of inductanceL = 1 mH, that couldoperate at 60 Hz vottage of RMS value U: 120 V. ****************************************************************** Problem 4. (20p) Calculate true parameters of a 50 kVA, 3000/480 V transformer equivalent
{K circuit, if the short circuit voltage is UISC = 7% of U“, short—circuit power PSC = 2.5% of Sr, open circuit current, 110 = 4 % of In and the open circuit power P0 = 1.5% of Sr.
******************************************************************** L
Wt lb Answer 8 of 10 following questions
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'  :h a e/ f; ’ 3 Question 1. (5p) Explain effects of low power factor on energy sypply. ‘ “N
i A Question 2. (5p) Explain difference between overcompensation and undercompensation. “K \
l i \ ' i I .3. I 6‘ L/ ',
Lt Question 3. (5p) Write and explain the Lorenz Law. D? D” i w ’24 i M W t i 6
J z) Question 4. (5p) Develop relation between hysteresis power loss and hysterysis loop area. G267 ’ ’5‘” ‘ i‘ 3, 0 Question 5. (5p) Explain the Lenz Rule. / ‘ Qufstion 6. (5p) What is the difference between soft and hard ferromagneticsiED
L?) 9 Question 7. (5p) What are eddy currents?
Question 8. (5p) Explain the meaning of all parameters of a transformer equivalent circuit.
5.0 Question 9. (5p) Explain the meaning of the term “Short circuit voltage” of a transformer. 5 0 if i i, i) Question 10 . (5p) Draw diagram of voltage CRMS values for capacitively loaded transformer. '7‘“ ﬂ : '
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