Energy Processing and Smart Grid

CHAPTER 8PERMANENT-MAGNET MOTORS

8.1 INTRODUCTION

A permanent-magnet motor is simply a machine whose field windings have been replaced by a permanent magnet. Permanent-magnet machines are important in that they have low eddy-current losses compared to conventional DC motors and synchronous motors. Although they have limitations, they are important and useful for a number of applications.

This chapter is divided into three major segments:

• 8.1. Permanent Magnet DC Motors
• 8.2. Permanent Magnet Synchronous Motors
• 8.3. Variants of Permanent-Magnet Synchronous Motors

For each of these subsections, the concepts and fundamentals, motivation and applications, design models, and materials are discussed. Solved problems are also included.

8.2 PERMANENT-MAGNET DC MOTORS

8.2.1 Permanent-Magnet DC Motor Fundamentals and Concepts

A permanent-magnet DC motor is like an ordinary shunt motor except that its field is provided by a permanent magnet instead of a salient-pole, wound-field structure. Although there are various types of DC motors, the motor shown in Figure 8.1 is suitable for understanding the basic principles. All kinds of DC motors work on the same principles.

Figure 8.1 Permanent magnet DC motor.

For constructing a DC motor it is essential to establish a magnetic field. The magnetic field is established, obviously, by means of magnet. The magnet can by of many types including ...