Generalized Theory of Electrical Machinery

In the following pages electrical machinery is analyzed from a new point of view. Analytical quantities like magnetizing current, armature reaction, leakage flux, transient reactance are not introduced; only such quantities are used as actually exist in the machine at one particular load. Thereby the theory of electrical machinery is expressed in terms of the minimum possible number of quantities. No hypothetical currents or fluxes are used and no actual physical quantity is left out. The concept of ``free energy,'' used in thermo dynamics, is introduced and generalized. The criterion of good design of all electrical machines is expressed by a constant, the ``thermodynamic efficiency'' which gives a measure of the effective utilization of iron and space for the transformation of energy. This constant plays a most fundamental role in the steady and transient behavior of the machine. A method is given by which the direction of flow of energy between different parts of any complicated machine can be easily read off the diagrams. The theory of constant-potential and constant-current electromagnets is used as a stepping stone to show that the theory of the polyphase alternator is identical with the theory of the constant-potential polyphase transformer if flux linkages and magnetomotive forces are interchanged. The circle diagrams of the transformer and the alternator are developed as well as the elliptical locus diagram of the alternator with salient poles. Problems in the sudden short circuit and the sudden load variation of the polyphase alternator are also solved.