Development of a leakage flux measurement system for condition monitoring of electrical drives

The aim of this paper is to investigate the possibility to employ a simple external flux coil to monitor the operating conditions of induction motors of different sizes, supplied at low voltage, from the mains or from power converters. The state of the art of the literature concerning the analysis of the stray flux around induction machines, in different positions and with different types of search coil, is here reported. Then, the flux probe here used is presented, together with several acquisitions of stray flux in three positions around the motor and with different techniques of signal analysis. These acquisitions are also compared with measurements collected by means of a commercial flux sensor. The final purpose is to find the best combination of position, sampling frequency, filter, etc. which can give the more interesting information about the “health” condition of the motor.