Introduction to Electric Power Systems Quiz 1: Three Problems, Exams of Electronics engineering

Download Introduction to Electric Power Systems Quiz 1: Three Problems and more Exams Electronics engineering in PDF only on Docsity! Massachusetts Institute of Technology Department of Electrical Engineering and Computer Science 6.061/6.690 Introduction to Power Systems Quiz 1 March 16, 2011 Closed Book: One Handwritten Crib Sheet Allowed Please put your answers in the spaces provided on the quiz. You may, if you wish, turn in your work on additional sheets of paper. Hopefully you will get all the answers correct so I don’t have to look at those sheets. Problem 1: A three-phase transformer is shown in Figure 1. It is connected to an ordinary three- phase voltage source on the primary side and loaded by a single resistor on the secondary side. The RMS amplitude of voltage on the primary side is 100 V. The resistor has value Ns N1 R = 30, 000Ω. The transformer turns ratio is 10. Assume that the primary side voltages = are: −j 2 3 j 2 3 π π V = V V = V V = V e e ba c c N1 N1 N1N2 N2 N2 Ia a b c I Ib Figure 1: Three Phase Transformer with load resistor 1. Find the currents Ia, Ib and Ic and draw them on the template shown in Figure 2. Be sure to label each current and show its RMS magnitude and angle. Note the lines on the template are spaced 15◦ apart. 2. What are real and reactive power from each of the three voltage sources? (P + jQ)A = (P + jQ)B = (P + jQ)C = 1 a Vb Vc V Figure 2: Your answer to Problem 1 goes here 2