Motor Current Signature Analysis (MCSA) is a technique for identifying developing problems inside motors, particularly the development of defects in the rotor such as rotor bar cracking. MCSA is also sometimes referred to as Electrical Signature Analysis (ESA).
MCSA is a well-established technique with over 30 years’ industrial application. MCSA works by measuring the current drawn by an electric motor and analysing distortions to the current waveform. The key elements of MCSA involve creating and analysing a frequency spectrum of the current waveform. If the waveform were perfectly sinusoidal, this spectrum would appear as a single peak at the line frequency only. Any distortions to the current waveform appear as additional peaks, at frequencies that are related to the characteristic frequency of the phenomenon causing the distortion. By assessing the size of the peak and the frequency at which it occurs, it is possible to deduce the probable cause of the distortion and assess its severity.
Conventional MCSA works just by analysis of the current waveform. This can limit its ability to identify problems when the applied voltage waveform is itself distorted. More specialised techniques such as Model-based Voltage and Current Analysis (as performed by Model-based VI systems) takes the shape of the voltage waveform into account and works out the distortions to the current waveform that have not been caused by the voltage distortions. (For more information see What is the difference between conventional MCSA and Model-based Voltage and Current systems? (model based VI systems)). These residual distortions are the result of other phenomena in the motor and/or driven equipment, and typically correspond to developing faults in the equipment. This makes Model-based systems a very powerful condition monitoring technique, comparable to vibration-based systems in their ability to identify mechanical problems, but also able to detect electrical based problems that vibration monitoring cannot deal with.