AbstractA substantial portion of electric energy, up to two third of the amount produced, is converted into mechanical energy by various rotating machines. These are supplied mainly from three‐phase sources of a sinusoidal voltage. There are situations, however, where this voltage is strongly distorted. In recent years, progress was achieved regarding comprehension of the power phenomena in circuits with non‐sinusoidal voltages and their power factor improvement. This is due to a power theory based on the current orthogonal decomposition into the active, scattered, reactive and unbalanced current. That theory does not take into account, however, peculiar power properties of the rotating machines. This paper suggests a modification of this theory to a form that might be more suitable for describing the flow of energy between a rotating machine and a three‐phase source of non‐sinusoidal voltage.