Grad Practice Test 1

Grad Practice Test 1 - EE 5343, Test 1, Spring 2002:...

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R base_p 23.04 = R base_s 208 volt 3 I rat_s := R base_s 4.326 = R wp 0.01 R base_p := R wp 0.23 = R ws 0.01 R base_s := R ws 0.043 = Problem 3: A three-phase load is drawing 250 kW real power at a power factor of 0.75 lagging. a) Find the apparent power S drawn by the load in kVA 333.3 . b) Find the reactive power Q drawn by the load in kVAR 220.5 . c) Find the capacitor bank rating in kVAR to increase the combined power factor to 0.95 lagging. SV I = PV I pf = QV I sin acos pf () = SP 2 Q 2 + = acos 0.75 ( ) 41.41 deg = S P pf = S 250 kW 0.75 := S 333.3 kVA = Q 075 S sin acos 0.75 := Q 075 220.5 kVAR = EE 5343, Test 1, Spring 2002: Dr. M. Giesselmann, February 14, 2002 Definitions: freq 60 Hz := ω 2 π freq := MW 1000 kW kVA kW kVAR kW m 1000 MVA 1000 kW MVAR 1000 kW Problem 1: a) What is the principal advantage of AC power systems compared to DC power systems? The ability to step voltages up and down for long distance transmission. b) Give two solutions to eliminate oscillations of the instantaneous power in AC power systems. Use a balanced two-phase system with voltages 90 deg apart, or a balanced three-phase system with voltages 120 deg apart. c) Which of the solutions listed in (b) is better for long distance power distribution and why? Three-phase systems transmit more power per line since the currents add up to zero.
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This test prep was uploaded on 04/21/2008 for the course EE 4343 taught by Professor Giesselmann during the Spring '08 term at Texas Tech.

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Grad Practice Test 1 - EE 5343, Test 1, Spring 2002:...

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