chap01 - 1 Introduction 1.1 INTRODUCTION TO POWER...

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1 Introduction 1.1 INTRODUCTION TO POWER PROCESSING The field of power electronics is concerned with the processing of electrical power using electronic devices [1–7]. The key element is the switching converter, illustrated in Fig. 1.1. In general, a switching converter contains power input and control input ports, and a power output port. The raw input power is processed as specified by the control input, yielding the conditioned output power. One of several basic functions can be performed [2]. In a dc–dc converter, the dc input voltage is converted to a dc output voltage having a larger or smaller magnitude, possibly with opposite polarity or with isolation of the input and output ground references. In an ac–dc rectifier, an ac input voltage is rectified, producing a dc output voltage. The dc output voltage and/or ac input current waveform may be controlled. The inverse process, dc–ac inversion, involves transforming a dc input voltage into an ac output voltage of controlla- ble magnitude and frequency. Ac–ac cycloconversion involves converting an ac input voltage to a given ac output voltage of controllable magnitude and frequency. Control is invariably required. It is nearly always desired to produce a well-regulated output
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put power and input power is The power lost in the converter is Equation (1.2) is plotted in Fig. 1.3. In a con- verter that has an efficiency of 50%, power is dissipated by the converter elements and this is equal to the output power, This power is converted into heat, which must be removed from the converter. If the output power is substantial, then so is the loss power. This leads to a large and expen- sive cooling system, it causes the electronic elements within the converter to operate at high temperature, and it reduces the system reliability. Indeed, at high output powers, it may be impossible to adequately cool the converter elements using current technology. Increasing the efficiency is the key to obtaining higher output powers. For exam- ple, if the converter efficiency is 90%, then the converter loss power is equal to only 11% 2 Introduction voltage, in the presence of variations in the input voltage and load current. As illustrated in Fig. 1.2, a controller block is an integral part of any power processing system. High efficiency is essential in any power processing application. The primary reason for this is usually not the desire to save money on one’s electric bills, nor to conserve energy, in spite of the nobility of such pursuits. Rather, high efficiency converters are necessary because construction of low-efficiency converters, producing substantial output power, is impractical. The efficiency of a converter having out-
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1.1 Introduction to Power Processing 3 of the output power. Efficiency is a good measure of the success of a given converter technology. Figure 1.4 illustrates a converter that processes a large amount of power, with very high efficiency. Since very little power is lost, the converter elements can be packaged with high density, leading to a converter of
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This note was uploaded on 01/17/2010 for the course EL 5673 taught by Professor Dariuszczarkowski during the Spring '09 term at NYU Poly.

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chap01 - 1 Introduction 1.1 INTRODUCTION TO POWER...

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