Motor control and protection, drives, and applications

Abstract

Electric motors are used in a vast range of applications, types, shapes, sizes, or constructions. In our power systems, the generators in power plants are connected to a three-phase network while most of the industrial equipment and largeor medium-size electric motors, pumps in heating, water and air conditioning systems, refrigerator, dryers, vacuum cleaner or most of the appliances are connected to a single phase AC, switched on or off by simple contactors. In cars, a DC battery is providing power to the starter motor, windshield wiper motors, and other car subsystems. The DC car motors are usually activated by a relay switch without any control. However, many of other electric motor applications often require advanced control, depending on the application and the load requirements. Motor protection and control are essential functions for proper operation and safeguard electric motors and their connection cables from the effects and/or damages caused by overheating or improper motor operation. For example, overload, stalling, and single-phasing result in overheating, and the motor protection must detect these conditions and prevent their effects. Electric motors are the major prime-mover in industrial and commercial facilities and in building electrical, mechanical, and thermal systems. Most of the electric losses occur in the end user, and electric machines and drives are a large contributor. Electric motors and drives are important electrical system components, being the interface between the electrical and mechanical systems in an industrial process, a building, industrial, or commercial facility. These are creating unique challenges for motor control and protection which, in turn, led to the solutions that are critical in all electrical motor applications. By completing this chapter, the readers must have a good understanding of the electric motor control, starting, stopping, speed changes, breaking, and motor protection methods. It is very important to understand motor characteristics, in order to choose the right one for the application requirements. The learning objectives for this chapter include understanding the basic principles of operation of AC and DC motors, understand their operation and basic characteristics, control and protection methods and schemes, compute their electrical and mechanical parameters using the equivalent circuit, and to be able to select the most appropriate electric motor for a specific application. Readers must also understand and learn the structure, configurations, characteristics, and the operation of electric drives and their major applications. The chapter also includes appropriate references to the electric motor specifications of the codes and standards.