Abstract :
When analysing electrical machines, certain physical concepts are common to all machines whatever the axes of reference, e.g. resistance voltage-drop. These invariant quantities can be expressed mathematically as tensors. The paper investigates the form of the invariant equations of a two-machine system. One basic equation in its general transient form, and the corresponding hunting equation, are used for the two individual machines, and it is shown that the same two equations apply to the connected system. The tensor equations are expanded to give the full matrix equations of the system. The application of the latter has already been published by the authors.