ON THE SPATIAL PROPAGATION OF TRANSIENT MAGNETIC-FIELDS IN AC MACHINES

AC motors have proliferated as the most important machine type used in speed variable drive systems. The dynamic analysis and description of revolving field machines is supported by well-established theories: P ark's transformation (1929), and the space vector theory by Kovacs and Racz (1959). Yet some inconsistencies with the theory of dynamic syst ems exist. First, the machine eigenvalues suggest the existence of two damped oscillators. Second, it appears unsatisfactory that the respec tive eigenfrequencies change with the velocity of the reference frame. This contradicts the common understanding according to which the eige nfrequency is an inherent system property. A clarification is reached using a novel approach for dynamic ac machine analysis. The approach i s based on complex state variables. It permits relating a transient co ndition to the propagation processes in space of distributed magnetic fields. The formal analysis constitutes an extension to the space vect or theory and to the theory of dynamic systems.