The General Circle Diagram of Electrical Machinery

The well known circle diagram of a transmission network is applied to electrical machinery, giving circle diagrams of alternators, synchronous motors, synchronous condensers, and transformers. These diagrams give a graphical representation of the machine performance under all possible conditions. Such quantities as power loss, power input, power output, field current, etc., for any operating condition can be obtained by inspection. These diagrams have the same field of usefulness as the circle diagram of the induction motor. The transmission network circle diagram can be applied to the induction motor, yielding in the approximate representation the Heyland diagram, which is merely a special case of the more general diagram. The transmission network method of attack gives a straight-forward solution of many induction motor problems that would otherwise be difficult to handle, such as a motor equipped with a phase advancer. Methods of obtaining network constants by measurements rather than computations are described.