Modern Permanent Magnet Electric Machines

Book excerpt: The late 1980s saw the beginning of the PM brushless machine era, with the invention of high-energy density permanent magnets (PM) and the development of power electronics. Although induction motors are now the most popular electric motors, the impact of PM brushless machines on electromechanical drives is significant. Today, PM machines come second to induction machines. Replacement of electromagnetic field excitation systems by PMs brings the following benefits: No electrical energy is absorbed by the field excitation system and thus there are no excitation losses, causing substantial increase in efficiency Higher power density (kW/kg) and/or torque density (Nm/kg) than electromagnetic excitation Better dynamic performance than motors with electromagnetic excitation (higher magnetic flux density in the air gap) Simplification of construction and maintenance Less expensive for some types of machines Modern Permanent Magnet Electric Machines: Theory and Control serves as a textbook for undergraduate power engineering students who want to supplement and expand their knowledge in the fundamentals of magnetism, soft magnetic materials, permanent magnets (PMs), calculation of magnetic circuits with PMs, modern PM brushed DC machines and their controls, modern PM brushless DC motors and drive control, and modern PM generators. The book can help students learn more about electrical machines and can serve as a prescribed text for teaching elective undergraduate courses such as modern permanent magnet electrical machines. Since the book is written in a simple scientific language and without redundant mathematics, it can also be used by practicing engineers and managers employed in electrical machinery or electromagnetic device industries.