A low-intrusion load and efficiency evaluation method for in-service motors using vibration tests with an accelerometer

This paper presents a novel low-intrusion load and efficiency evaluation method for in-service induction motors based on vibration measurements. This method enhances the traditional vibration analysis by providing motor load and efficiency information in addition to the mechanical health information. The application is in multimotor plants, where individual motor monitoring is too expensive to implement yet where motor operating conditions need to be known to work at improved plant efficiency. The vibration signature of the machine, measured by an accelerometer and processed by fast Fourier transform (FFT) is used to extract frequencies defining shaft speed and the supply frequency. This data, in conjunction with the basic motor performance data, enables the determination of the actual load and indirectly, the efficiency which the motor is operating at. For motors supplied form a variable-speed drive (VSD), the loss segregation method is used to yield the motor losses indirectly and thus, the efficiency.