tailieunhanh - Ebook Engineering circuit analysis (7th edition): Part 2

(BQ) Part 2 book "Engineering circuit analysis" has contents: AC circuit power analysis, polyphase circuits, magnetically coupled circuits, complex frequency and the laplace transform, circuit analysis in the s-domain, frequency response, two-port networks,.and other content. | AC Circuit Power Analysis KEY CONCEPTS INTRODUCTION Often an integral part of circuit analysis is the determination of either power delivered or power absorbed or both . In the context of ac power we find that the rather simple approach we have taken previously does not provide a convenient picture of how a particular system is operating so we introduce several different power-related quantities in this chapter. We will begin by considering instantaneous power the product of the time-domain voltage and time-domain current associated with the element or network of interest. The instantaneous power is sometimes quite useful in its own right because its maximum value might have to be limited in order to avoid exceeding the safe or useful operating range of a physical device. For example transistor and vacuum-tube power amplifiers both produce a distorted output and speakers give a distorted sound when the peak power exceeds a certain limiting value. However we are mainly interested in instantaneous power for the simple reason that it provides US with the means to calculate a more important quantity the average power. In a similar way the progress of a cross-country road trip is best described by the average velocity our interest in the instantaneous velocity is limited to the avoidance of maximum velocities that will endanger our safety or arouse the highway patrol. In practical problems we will deal with values of average power which range from the small fraction of a picowatt available in a telemetry signal from outer space to the few watts of audio power supplied to the speakers in a high-fidelity stereo system the several hundred watts required to run the morning coffeepot or the 10 billion watts generated at the Grand Coulee Dam. Still we will Calculating Instantaneous Power ---------------------------- Average Power Supplied by a Sinusoidal Source Root-Mean-Square RMS Values Reactive Power The Relationship Between Complex Average and Reactive Power Power Factor