Apparatus for on-line continuous diagnosis of induction motors based on the SFRA technique

The induction motor is used the most in industrial applications. In these areas, motor faults can involve several issues concerning health, safety, and process down time, in addition to the bare cost of the machinery itself. Induction motors may have different types of faults, mainly in the stator windings. These often begin as simple turn-to-turn failures, which can then lead to worst phase-to-phase or phase-to-ground failures. In the complex scenario of diagnostic techniques available today, the sweep frequency response analysis (SFRA) has recently emerged as a promising approach for the characterization of rotating electrical machines. In this article, a PC-based, low-cost test system that implements the SFRA technique is proposed, to verify its applicability for the continuous online diagnostic of induction motors. The system performances have been experimentally evaluated, by testing two 5.5-kW induction motors, with two-and four-poles. Both the heating test at constant mechanical load and the test at thermal equilibrium with variable loads have been investigated. The positive results obtained seem to confirm the applicability of the proposed system for the online diagnosis of asynchronous motors.