Sistemas de potencia

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6.061 / 6.690 Introduction to Electric Power Systems
Spring 2007

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Massachusetts Institute of Technology
Department of Electrical Engineering and Computer Science 6.061/6.690 Introduction to Power Systems Problem Set 1 Issued: Ses #1 Due: Ses #3Reading Assignment: Class Notes, Chapter 1

Problem 1: Your ordinary household electrical system is single phase and employs a voltage of 120 V, RMS. What can a circuit with a 20 A breaker handle? •In Watts? • A motor, rated in horsepower? Ignore questions of power factor and motor efficiency here: we will do those later. • A heater, rated in British Thermal Units/hour. Problem 2: Find theThevenin equivalent for the circuit shown in Figure 1.

2 4

4 10 + 10 −

Figure 1: Circuit Problem 3: Figure 2 shows two circuits, one with resistor values, the other with symbols. Show that thesetwo circuits are equivalent if the values represented by the symbols are chosen correctly. Find the value of the symbols.

1 1 1
Figure 2: Circuit

R1

R2 R3

Problem 4: Figure 3shows aWheatstone Bridge, loaded with a resistor at its output. Find the output voltage vo . You may do this any way but will probably find it expedient to first determine the Thevenin equivalent of the circuitthat excludes the horizontally oriented resistor. 1

+ 14 −

1

vo + − 1

2

2
Figure 3: Loaded Bridge

1

Problem 5: Find a computer the can run MATLAB and get it to plot a nice copy ofthe function
F (t) = 100 cos(ωt)e− τ over the interval 0 < t < 1/2, for values of ω = 377Radians/second 1 second τ = 2 Problem 6: For 6.690 only Figure 4 shows a ’magic ladder’ network driven by acurrent source at one end. Assume the value of each of the resistors is either R or 2R where is R = 1kΩ The value of the voltge source is V0 = 10V . Find the Thevenin Equivalent Circuit at the...