Motor current signature analysis method for diagnosing motor operated devices

A method for diagnosing operating characteristics of a device driven by an operating motor that draws an electric current, comprising the steps of:

• operating the motor to drive the device;
• sensing an electric current drawn by the motor during an operation of the device, to produce a detect signal;
• determining a frequency range based on a specific operating element whose operating characteristics are to be analyzed;
• generating, at a first time, a first frequency signature, within the frequency range, from the detect signal in the form of a plurality of amplitude values at a plurality of frequency values, the frequency values and associated amplitude values of the first frequency signature corresponding to the frequencies and the associated amplitudes in the detect signal;
• generating, at a second time, a second frequency signature from the detect signal, said second frequency signature having a same form as the form of the first frequency signature;
• comparing the first and second frequency signatures to determine information as to the operating characteristics of the device;
• identifying specific side band frequencies that are indicative of a degradation of an operating characteristic of the device;
• comparing the first and second frequency signatures to determine a presence of the specified side band frequencies in the second frequency signature as compared to the first frequency signature;
• and
• determining a degradation condition in an operating characteristic of the device when said presence is detected.

A method for diagnosing operating characteristics of a device driven by an operating motor that draws an electric current, comprising the steps of:

• operating the motor to drive the device;
• sensing an electric current drawn by the motor during an operation of the device, to produce a detect signal;
• determining a frequency range based on a specific operating element whose operating characteristics are to be analyzed;
• generating, at a first time, a first frequency signature, within the frequency range, from the detect signal in the form of a plurality of amplitude values at a plurality of frequency values, the frequency values and associated amplitude values of the first frequency signature corresponding to the frequencies and the associated amplitudes in the detect signal;
• generating, at a second time, a second frequency signature from the detect signal, said second frequency signature having a same form as the form of the first frequency signature;
• comparing the first and second frequency signatures to determine information as to the operating characteristics of the device;
• identifying at least one side band frequency that is an indication of an operating characteristic of the device;
• and
• analyzing the side band frequency in the first and second frequency signatures to determine information as to the operating characteristic.

An apparatus for diagnosing operating characteristics of a device driven by an operating electric motor wherein said device produces noise in a current drawn by said motor, comprising:

• means for sensing said current drawn by said motor;
• means for specifying a frequency range based on a specific operating element whose operating characteristics are to be analyzed;
• spectrum analyzer means for measuring amplitudes of a frequency spectrum of said current;
• means for storing said measured frequency spectrum amplitudes in a recording device in the form of a frequency domain recording, to form a recording of a frequency spectrum;
• means for comparing said stored frequency domain recording with other frequency domain recordings to detect changes in the operating characteristics of said device,
• wherein said comparing means also includes means for comparing said stored frequency domain recordings with time domain recordings to determine additional operating characteristics of said device.