DIEM project´s outcomes: An automated air-gap monitoring approach for Italian Navy´s on-board low-voltage generators

The Italian Navy committed in 2006 to the Department of Astronautics, Electrical, and Energy Engineering-University of Rome “Sapienza” a Research Program aimed to define an automated procedure for air-gap monitoring of onboard generators. An effective solution was needed to overcome the heavy shortcomings of usual manual measurement practices. This paper describes the research work which led to very reliable rotor eccentricity indicators, based on measurement of internal currents in armature windings with parallel connections. The new approach permits absolute on-line estimations of both static and dynamic rotor shaft misalignments. A fully operative demonstrative system has been developed in the Department´s laboratory. A four pole 17kVA generator was used for experiments, with artificial eccentricities produced by an apposite mechanical flange. A virtual instrument was used for data acquisition and processing, so obtaining a real-time estimation of the actual shaft misalignment. Comparison of data obtained from simulations and tests prove the reliability of the proposed methodology.