Power Electronics, A First Course, 2nd Edition

11 APPLICATIONS OF SWITCH-MODE POWER ELECTRONICS IN MOTOR DRIVES, UNINTERRUPTIBLE POWER SUPPLIES, AND POWER SYSTEMS

11.1 INTRODUCTION

Electric motor drives (AC and DC), uninterruptible power supplies (UPS), and power systems are major application areas of switch-mode power electronics. In these applications, the role of power electronics converters is to synthesize appropriate voltages of desirable amplitude, frequency, phase, and the number of phases, where the power flow is often bidirectional. This synthesis process is described in detail in the next chapter. The purpose of this chapter is to present various applications and describe the voltage and current requirements they impose on the power electronics converters.

11.2 ELECTRIC MOTOR DRIVES

As described in Chapter 1, motor drives represent an important application area of power electronics with a market value of tens of billions of dollars annually. Figure 11.1 shows the block diagram of an electric motor drive, or for short, an electric drive. In response to an input command, electric drives efficiently control the speed and the position of the mechanical load. The controller, by comparing the input command for speed and position with the actual values measured through sensors, provides appropriate control signals to the power-processing unit (PPU) consisting of power semiconductor devices.

FIGURE 11.1 Block diagram ...