Diagnostic device and diagnostic method for rotary machine

A diagnostic device for a rotary machine, comprising:

• a current acquisition unit configured to acquire a current from a sensor that measures a driving current of the rotary machine driving a driven machine;
• a sampling unit configured to perform sampling on a modulated signal obtained by setting the driving current as a carrier wave and performing a detection process on an amplitude-modulated part of the carrier wave;
• a frequency range conversion unit configured to convert time-range data having been subjected to the sampling into a frequency range;
• a sideband detection unit configured to detect, in the frequency range, portions of a spectrum corresponding to the modulated signal as sidebands;
• and
• an abnormality detection unit configured to determine whether or not the rotary machine and the driven machine have an abnormality based on frequencies at positions of the sidebands detected by the sideband detection unit.

A diagnostic method for a rotary machine, wherein a diagnostic device for the rotary machine includes and executes:

• a current acquisition process of acquiring a current from a sensor that measures a driving current of the rotary machine driving a driven machine;
• a sampling process of performing sampling on the driving current thus acquired;
• a frequency range conversion process of converting time-range data having been subjected to the sampling process into a frequency range;
• a sideband detection process of setting, in the frequency range, the driving current as a carrier wave and detecting, as sidebands, portions of a spectrum appearing on both sides of the carrier wave having been amplitude-modulated;
• and
• an abnormality detection process of determining whether or not the rotary machine and the driven machine have an abnormality, based on a frequency difference between at least one of frequencies of the sidebands detected by the sideband detection unit and a frequency of the carrier wave.