In a modern industrialized country about 65% of electrical energy is consumed by electrical drives. Constant-speed, variable-speed or servo-motor drives are used almost everywhere: in industry, trade and service, households, electric traction, road vehicles, ships, aircrafts, military equipment, medical equipment and agriculture. Electromechanical drives for speed and position control play a key role in robotics, factory automation, process control, energy conservation and electric vehicles. There is an increasing need to train students, electrical engineers, and electromechanical engineers in the area of modern electrical motors and drives, their control, simulation and CAD.
Vector control methods developed in the early 1970s allow for controlling three-phase induction motors in the same way as d.c. commutator motors. This new control technology, in connection with the high reliability, very limited maintenance and low price of cage induction motors, has made induction motors the most popular motors today.
With the world-wide trend to energy conservation, there is a need to increase the efficiency of a.c. drives, small and large. The recent advanceŽments of permanent magnet (PM) materials, solid-state devices and microelectronics have contributed to new energy efficient, high performance electric drives which use modern PM brushless motors. Owing to rare-earth PMs, these motors have higher efficiency, power factors, output power per mass and volume, and better dynamic performance than cage induction motors without sacrificing the reliability. It is quite possible that these PM brushless motor drives will become predominant in the next century.
Progress in PM materials has also revolutionized construction of other PM motors such as d.c. commutator motors and stepping motors, as well as making possible the manufacture of large PM motors (megawatts) and micromotors (milliwatts). New electromechanical drive technology has had an impact on teaching and training. Modern electrical drives courses in electrical engineering departments and the continuing education of practicing engineers require a book which can cover the broad topic of PM motors and their applications.