Variable frequency drive as a source of condition monitoring data

Variable speed drives are gaining popularity as an efficient way to power industrial motors. They collect and compute a large number of signals, normally used for control and operation purposes (for example, current, torque, speed, frequency, power, flux, etc.). This data is available and can be used for diagnostic purposes. These signals can be analyzed for their spectral content, for monitoring the operating point, for examining cyclic processes, etc. On the down side, the format, quality and quantity of data is determined by the hardware. Further complication arises from the fact that variable speed drives change the output frequency to follow desired process parameters. Methods for circumventing these difficulties are presented along with actual results from various drive-powered processes. These results prove that a variable speed drive can be a valuable source of diagnostic data not only for the drive itself, but also for the entire driven process.