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Unformatted text preview: EE 295  Homework 1 Solutions February 3, 2010 1 Readings 1. Chapters 12 of Bergen/Vittal 2 From the textbook (Bergen/Vittal) 2.1 Problem 2.1 v ( t ) = 2120cos( t + 30 ) , i ( t ) = 210cos( t 30 ) (a) Find p ( t ) , S = P + jQ . Working backwards, we get phasors: V = 120 30 , I = 10  30 . S = V I * = 1200 60 = 600 + j 1039 . P = 600 W. Q = 1 . 04 kVAr. p ( t ) =  V  I  (cos( ) + cos(2 t + V + I )) = 600 + 1200cos(2 t ) (b) Find an equivalent circuit that gives this V/I relationship. The easiest way to do this is to assume that we have an inductor and a resistor in series: Z = V/I = 12 60 = 6 + j 10 . 4 Therefore R = 6 and L = X L / = 0 . 0276 . 2.2 Problem 2.3 5MW load at 0.7 PF lagging. Find the reactive power required from a parallel capacitor to bring the power factor of the parallel combination to 0.9. 1. First find the reactive power of the system without the capacitor: P = 5 MW =  S  . 7  S  = 7 . 142...
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This note was uploaded on 11/06/2011 for the course ECON 6545 taught by Professor Gully during the Spring '11 term at Temple.
 Spring '11
 gully

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