Abnormality diagnosis device and abnormality diagnosis method

An abnormality diagnosis device for determining abnormality of a load apparatus including an electric motor and load equipment connected to the electric motor, the abnormality diagnosis device comprising:

• a current detector which detects current of the electric motor;
• and
• an abnormality diagnosis circuitry to perform FFT analysis on the current detected by the current detector and determines abnormality using extracted spectrum peaks, wherein
• the abnormality diagnosis circuitry includes
• a peak analysis circuitry to perform analysis using a power supply frequency of the electric motor and frequencies of sideband peaks with respect to the power supply frequency, and analyzes the extracted spectrum peaks for each frequency,
• a frequency determination circuitry to determine, from the spectrum peaks analyzed by the peak analysis circuitry, which kind of the electric motor and the load equipment the spectrum peak for each frequency is due to,
• a frequency storage to store, for each load torque of the electric motor, the frequencies and signal intensities of the spectrum peaks due to the electric motor, and the frequencies and signal intensities of the spectrum peaks due to the load equipment, when the load apparatus is in a normal state, and
• an abnormality determination circuitry, and
• the abnormality determination circuitry includes
• a load torque selection circuitry to select a load torque present when the current is detected by the current detector in abnormality diagnosis,
• a feature quantity calculation circuitry to with respect to a plurality of diagnosis spectrum peaks for which the kind has been determined from FFT analysis on the current detected in the abnormality diagnosis, read the frequencies and the signal intensities of the spectrum peaks in the normal state corresponding to the load torque selected by the load torque selection circuitry and the determined kind, from the frequency storage unit, and calculate, regarding the plurality of diagnosis spectrum peaks, absolute values of differences of signal intensities from those in the normal state for the respective frequencies, to use a sum of the absolute values as a feature quantity,
• a function information storage, and
• an abnormality degree calculation circuitry to calculate an abnormality degree representing a degree of progress from the normal state to an abnormal state,
• fitting for a correlation between the abnormality degree and the feature quantity calculated by the feature quantity calculation circuitry is performed using a function stored in the function information storage, and
• the abnormality degree calculation circuitry calculates the abnormality degree corresponding to the feature quantity on the basis of the fitted function,
• wherein the abnormality diagnosis circuitry further comprises at least one processor configured to implement the peak analysis circuitry, the frequency determination circuitry, and the abnormality determination circuitry including the load torque selection circuitry, the feature quantity calculation circuitry, the abnormality degree calculation circuitry.

An abnormality diagnosis method for determining abnormality of a load apparatus including an electric motor and load equipment connected to the electric motor, the abnormality diagnosis method comprising:

• detecting current of the electric motor;
• performing FFT analysis on the detected current and detecting spectrum peaks;
• extracting frequencies of sideband peaks with respect to a power supply frequency of the electric motor, from the spectrum peaks detected in the performing FFT analysis;
• determining which kind of the electric motor and the load equipment the spectrum peak for each frequency is due to, using the power supply frequency and the extracted frequencies of the sideband peaks;
• selecting a load torque of the electric motor present when the current is detected;
• with respect to signal intensities for the respective frequencies of a plurality of the spectrum peaks determined for each kind, calculating, as a feature quantity, a sum of absolute values of differences from signal intensities for the frequencies of the spectrum peaks due to the kind in a normal state corresponding to the determined kind and corresponding to the selected load torque;
• and
• comparing the calculated feature quantity with a predetermined threshold and determining abnormality of the load apparatus.