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Unformatted text preview: ECE 333 Green Electric Energy Spring 2010 Exam #1, Tuesday, February 23, 2010. 11:00AM-12:20PM NAME: Solutions Question 1 (10 p) (a) What are the sectors in which the demand (or end-use) side of the electric system is commonly divided? Residential, commercial, and Industrial. (b) What are the principal loads that drive the peak demand for power? Lighting and air-conditioning of residential and commercial buildings. Question 2 (10 p) The acronyms for two important Acts for the electric industry in the US are PUHCA, and PURPA. (a)What do these acronyms stand for? PUHCA: Public Utility Holding Company Act. PURPA: Public Utility Regulatory Policies Act. (b) Name a key outcome that resulted from the enactment of each of these Acts. PUHCA: Regulation of gas and electricity companies to prevent holding company excesses. PURPA: It gave birth to the electric side of the renewable energy industry. Question 3 (10 p) Calculate the average and the RMS of the waveform v ( t ) displayed below. 6 12 18-1-0.5 0.5 1 time [s] v ( t )[V] Average: v ( t ) = 0 V (symmetric waveform centered around zero). RMS: v RMS = radicalBigg 1 T integraldisplay T v 2 ( t ) dt = radicalBigg 1 6 integraldisplay 6 ( 1 3 t 1 ) 2 dt = 1 3 = 0 . 577 V Question 4 (10 p) The voltage and current of a single-phase load are v ( t ) = 2 sin(2 ft ) i ( t ) = 2sin(2 ft ), where f is the standard value of frequency in the US. Denote by p ( t ) the instantaneous power consumed by the load. Among the four different power snapshots below, circle the one that corresponds to p ( t ). Explain your answer with a couple of sentences. 0.01 0.02 0.03 0.04 0.05 0.5 1 1.5 2 time [s] p ( t )[W] (a) 0.01 0.02 0.03 0.04 0.05-1-0.5 0.5 1 time [s] p ( t )[W] (b) 0.01 0.02 0.03 0.04 0.05 0.5 1 1.5 2 time [s] p ( t )[W] (c) 0.01 0.02 0.03 0.04 0.05 0.5 1 1.5 2 time [s] p ( t )[W] (d) Explanation: The answer is option (d). Power p ( t ) = v rms i rms + v rms i rms sin(4 ft ) = 1 + sin (4...
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