Variable speed is one of the important requirements in most of the
electric drives. Earlier dc motors were the only drives that were used
in industries requiring - eration over a wide range of speed with step
less variation, or requiring fine ac- racy of speed control. Such drives
are known as high performance drives. AC - tors because of being highly
coupled non-linear devices can not provide fast dynamic response with
normal controls. However, recently, because of ready availability of
power electronic devices, and digital signal processors ac motors are
beginning to be used for high performance drives. Field oriented control
or vector control has made a fundamental change with regard to dynamic
perfo- ance of ac machines. Vector control makes it possible to control
induction or s- chronous motor in a manner similar to control scheme
used for the separately - cited dc motor. Recent advances in artificial
intelligence techniques have also contributed in the improvement in
performance of electric drives. This book presents a comprehensive view
of high performance ac drives. It may be considered as both a text book
for graduate students and as an up-to-date monograph. It may also be
used by R & D professionals involved in the impro- ment of performance
of drives in the industries. The book will also be beneficial to the
researchers pursuing work on sensorless and direct torque control of
electric drives as up-to date references in these topics are provided.
