In the late 1880’s, Tesla patented several types of alternating current motors that were very quickly accepted and applied in practice. Understanding the operation of such an engine was significantly facilitated by a hydraulic analogy. Alternating fluxes are represented by jets of water with with the same phase, amplitude, and direction relations. The magnetic polarity of the rotor is represented by the body shaped to behave just like the rotor relative to the poles relative to the jets.

Completeness of this Analogy is supplemented by the fact that the phase displacement between the pressure and the fluid flux corresponds to the difference in phases between electromotive force and current. Each electrical size is associated with one mechanical: electricity – fluid, pressure – electromotive force, current strength – fluid flow, and more, relations between the electrical sizes and their effect on the motor rotor corresponds the ratio of the mechanical sizes with similar effect on the rotor mechanical analogy.