Diagnostics of mechanical abnormalities in induction motors using instantaneous electric power

Results of a study on the use of instantaneous electric power for diagnostics of mechanical abnormalities in induction motors are presented. The instantaneous power can be measured as the so-called product power, i.e., a product of one line-to-line voltage and one line current, or as a total input power to the stator. Theoretical analysis, computer simulations, and laboratory experiments described demonstrate the superiority of the instantaneous power as a diagnostic medium over the traditionally used stator current. It is shown that in the practical environment the product power is at least as indicative of the mechanical health of an induction motor as is the total power, which is more expensive to measure. A simple method of filtering noisy spectra of the product power is proposed.