A METHOD AND AN APPARATUS FOR MACHINE DIAGNOSING AND CONDITION MONITORING BASED UPON SENSING AND ANALYSIS OF MAGNETIC TENSION

摘要

A method for machine diagnosing and condition monitoring of a machine set mechanically coupled with an alternating-current electric machine, comprising the steps of sensing at least one parameter of the electric machine by using a Rogowski coil (RC) looped on at least one of the feed wires of the electric machine (EM) as a sensor; evaluating the sensed parameter by measuring a so called magnetic tension signal being proportional to the derivative of the current of the alternating-current electric machine (EM) at the output of the Rogowski coil (RC); analyzing said signal in time and frequency domains; providing the magnetic tension spectra; and on basis of the magnetic tension spectra, identifying fault frequencies characteristic for the operation of the electric machine (EM) and the coupled machine set. In the apparatus for machine diagnosing and condition monitoring of a machine set mechanically coupled with an alternating-current electric machine the feed wires of the electric machine (EM) are surrounded by Rogowski coils (RC) and the apparatus comprises a signal processing unit (DSP) producing a DFT/FFT spectra of the magnetic tension signal of the Rogowski coil (RC) looped around the feeding cables of the AC machine.