Traditional methods for rotational speed measurement of centrifugal pump and their problems were analyzed. A new method for the rotational speed measurement was proposed based on motor current signal analysis(MCSA), then its mathematic equation was deduced using data processing theory. According to a principle that the frequency of current in stator windings is equal to the rotating speed frequency of the rotor when a centrifugal pump is driven by an AC motor, the frequency component of motor stator current was acquired by means of MCSA technology. Finally, the rotating speed frequency was detected from the current frequency spectrum. A trail experiment was designed according to this principle. During a test, the motor was fed by a frequency converter which could generate AC power with various frequencies, and the flow rate was adjusted, then the motor stator current was sampled by Hall effect sensors and a data acquisition card. After demodulation and fast Fourier transform(FFT), the rotating speed frequency was detected in frequency spectrum within a restricted range. To validate this method, a method based on rotor-stator interaction and an optical tachometer method were also used to get the speed. Compared with these two methods, the new method proposed was subject to an error less than 2%, and this accuracy has met the requirement of centrifugal pump monitoring, demonstrating a potential application in centrifugal pumps. What′s more, it is a sensorless method which can be realized in a better accuracy and more flexible applicability. This outcome is subject to application significance in some degree.
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