Instantaneous power signal measurements for bearing diagnostics

Opis

Bearing diagnostics can be carried out based on the method, which relies on the measurement and analysis of the variability of the signal instantaneous power, defined as the product of instantaneous current and voltage power supplied to the engines. Bearing damage causes the appearance of deformations, which are in the form of additional harmonic components of the spectrum. These components are formed as a result of waveform distortions by signals with frequencies specific for a given type of bearing damage.

Relationships for determining these frequencies are known in the literature. Therefore, in the instantaneous power spectrum, there are components that can be used as a diagnostic symptom, on the basis of which it is possible to assess the technical condition of bearings in induction motors.

The method of performing diagnostic tests of bearing failures is based on the use of the product of the instantaneous current and voltage, spectral analysis of the resulting signal, and determining the frequency characteristic of the damage and identify them in the spectrum of instantaneous power. In the described method, the measurement is carried out by taking the signal, which is a measure of the current and voltage supplied to the machine.

The measuring stand used for bearing diagnostics consists of a tested engine, magnetic clutch, vibroacoustic dampers, whose task is to isolate the tested machines from the base on which the load is mounted, and a laser system for accurate shaft alignment. The laboratory stand allows measurements to be made for induction motors up to 5.0 kW.

The process of conditioning the current signal is performed using the current-voltage transducer LEM CT-5T (conversion ratio 5A/5V, and conditioning of the voltage signal is done by a voltage transducer LEM CV3-500 (conversion ratio 500V/10V). Then, both signals are fed to the measurement system, whose main component is the NI PXI 4462 data acquisition card installed in the NI PXI 1031 cassette measuring. Signals from the measurement cassette are transferred to a PC, where they are analyzed.

Machines STG80X-4C type were studied of the following parameters: Pn = 1.1 kW, Un = 400/230 V, In = 2.9/5.0 A. The measurements were performed for both undamaged engines and machines with different types of bearing failures. 6204 type of bearings were used in the tested machines.

Sample measurement results for the engine with damaged bearing outer race are presented. Measurements made for the rotational speed of the tested machine n = 1460 rpm, load 76% of nominal current In, sampling frequency 16384 Hz and spectrum resolution 1/32 Hz.

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Analysis of the instantaneous power signal for bearing diagnostics.xlsx

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Rok publikacji:

2020

Data zatwierdzenia:

2020-12-17

Data wytworzenia:

2010

Język danych badawczych:

angielski

Dyscypliny:

Automatyka, elektronika i elektrotechnika (Dziedzina nauk inżynieryjno-technicznych)

DOI:

10.34808/82sq-qd46

Weryfikacja:

Politechnika Gdańska

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