Vibration Analysis Using Dynamic Statistical Averaging of Tachometer Data
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Solution Overview
Problem
Vibration analysis of variable frequency drives (VFDs) is challenging due to the spread of energy across a range of frequencies, making it difficult to compare fundamental vibrating frequencies and harmonics, and traditional methods lack accurate speed parameter calculation and phase analysis, leading to ambiguous fault identification.
Innovation Solution
The system uses a tachometer to monitor rotational speed and a logic device for dynamic statistical averaging to calculate maximum, minimum, and average speed parameters, combined with synchronous triggering for phase analysis, enabling accurate correlation of vibration spectra with speed parameters to identify machine faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional vibration analysis methods are used on variable frequency drives, then the system can operate, but the energy spread across frequencies makes it difficult to compare fundamental vibrating frequencies and harmonics, leading to ambiguous fault identification
Solution Approach 1:
The patent changes the reference parameter from fixed frequency to variable speed parameters (maximum, minimum, average speeds calculated through dynamic statistical averaging). By correlating vibration frequencies with these dynamic speed parameters instead of assuming fixed operating conditions, the system can accurately identify faults even when energy is spread across frequencies due to variable speed operation.
2Measurement precision
If a tachometer is used to monitor rotational speed, then speed data can be obtained, but traditional methods lack accurate speed parameter calculation, leading to insufficient correlation with vibration spectra
Solution Approach 1:
The patent introduces dynamic statistical averaging as an intermediary processing step between raw tachometer data and vibration analysis. The logic device calculates maximum, minimum, and average speeds from tachometer signals, creating refined speed parameters that serve as mediators to correlate vibration spectra with actual operating conditions, thereby improving fault identification accuracy.
3Measurement precision
If synchronous triggering is used for phase analysis, then waveforms can be sequentially acquired from multiple locations, but traditional methods lack accurate phase difference calculation, leading to ambiguous fault identification
Solution Approach 1:
The patent uses synchronous triggering with feedback from the tachometer signal to sequentially acquire waveforms from multiple locations on the machine. The pulse edge of the tachometer signal triggers the acquisition, and the acquired waveforms are then correlated back to the speed parameters, creating a feedback loop that enables accurate phase difference calculation and fault identification.
Data Source
AI summary
Vibration analysis is performed on a machine having a variable frequency drive by using a tachometer to monitor rotational speed of the drive shaft and a logic device to calculate speed parameters associated with the drive shaft using the tachometer data. The speed parameters include a maximum speed, a minimum speed, and an average speed of the drive shaft. By correlating the vibration spectra of the motor drive with the speed parameters, machine faults can be identified based upon the energy distribution in the spectra. Further, vibration waveforms from two or more locations on the machine can be sequentially acquired through synchronous triggering by using a pulse edge of a stable tachometer signal. The waveforms can be compared to determine a phase difference to help in identifying any machine faults that may be present.