Diagnostics of mechanical abnormalities in induction motors using instantaneous electric power

Results of a study on the use of instantaneous electric power for diagnosti cs of mechanical abnormalities in induction motors are presented. The insta ntaneous power can be measured as the so-called product power, i.e., a prod uct of one line-to-line voltage and one line current, or as a total input p ower to the stator. Theoretical analysis, computer simulations, and laborat ory 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 a s 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 no isy spectra of the product power is proposed.