Although field orientation in induction machines is only 20 years old, the corresponding concept in synchronous machines dates back almost 60 years to the days of the thyratron tube. After a brief historical review, the basic theory of synchronous machine field orientation is outlined. The difference between 90#xb0; spatial orientation of field flux and armature mmf, which always yields a lagging terminal power factor, and other forms of space angle control is examined in some detail. The problems associated with current regulators and flux position sensing are explored and present day techniques are discussed. Applications to high performance servomotors, dc brushless motors, wide speed range drives and high power synchronous motors are considered. A substantial bibliography is included.
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