Wykorzystanie metod wibracyjnych do wzorcowania systemu diagnostycznego opartego na analizie prądu zasilajacego silnik indukcyjny Application of vibration methods for calibration of diagnostic system based on motor current analysis /

Tyt. nagł.Bibliografia s. 205-206.Dostępny także w formie drukowanej.STRESZCZENIE: W artykule przedstawiono sposób oceny trafności diagnoz uzyskiwanych z wykorzystaniem nowej metody badawczej, opracowanej do badania uszkodzeń łożysk w silnikach indukcyjnych. Badana metoda diagnostyczna oparta jest na pomiarze i analizie prądu stojana silnika indukcyjnego. W metodzie tej, dla podwyższenia trafności diagnoz, obliczanie zarówno prędkości kątowej silnika, jak i częstotliwości sieci zasilającej jest wykonywane na podstawie tego samego widma, które dalej jest wykorzystywane do pomiaru składowych harmonicznych charakterystycznych dla uszkodzeń łożysk. Sztucznie uszkodzone łożyska poddawano kwalifikacji pod względem głębokości i rodzaju uszkodzenia, wykorzystując urządzenie pomiarowe zbudowane na podstawie opracowanej metody, również wykonując badania sprawdzonym systemem diagnostyki wibracyjnej. Niektóre wyniki badań łożysk o różnych typach i głębokości uszkodzenia oraz wnioski płynące z tych pomiarów zostały podane w niniejszym artykule. SŁOWA KLUCZOWE: prąd stojana, widmo, silniki indukcyjne, system diagnostyczny, wzorcowanie, analiza prądu, diagnostyka wibracyjna, ABSTRACT: Damage of the bearings is the most frequent cause of squirrel cage induction machines failure. In some applications the current signal is the only potential source of information about the state of the machine, including the state of its bearings. Damage of the raceway or of the rolling element is followed by additional vibrations of the rotor. These vibrations are reflected in spectral composition of the stator currents. The new measuring method and the supply current analysis were elaborated for diagnostic of the motor bearings. In this method it is possible to recognize type of bearing fault, checking the control sum for each type of possible fault. The investigation referring to real objects were performed. The investigations were carried out using motors with bearings having defects caused on purpose. Examples of diagnostic results in case of: a) faultless bearings, b) bearing with damaged outer ring are presented in Figures 2 and 3. Marks from L1 to L20 in the Figures 2 and 4 define loads from idle running (L1) to 75% of rated power (L20). The correctness of distinguishing the type of damage was investigated. The diagnosis was assumed to be correct if it conforms to the defects indicated by the standard system of the vibration diagnostics, of course, when other damages were not detected. Figures 1 and 3 show the vibration testing results. The probability of correct distinguishing the type of damage defined this way is shown in the Figure 4. The average probability of diagnostic correctness determined this way reaches 70%. The probability that the system will identify correctly at least one existing defect is more than 90%. The investigations shows, that for testing new diagnostic method it is not enough to make damage to bearing but also have other reliable diagnostic method. This method defines real state of investigated bearing. KEYWORDS: diagnostics, spectrum, current measurements, vibration measurements, induction motors

Detection of inter-turn faults in transformer winding using the capacitor discharge method

The paper presents results of an analysis of inter-turn fault effects on the voltage and current waveforms of a capacitor discharge through transformer windings. The research was conducted in the frame of the Facility of Antiproton and Ion Research project which goal is to build a new international accelerator facility that utilizes superconducting magnets. For the sake of electrical quality assurance of the superconducting magnet circuits, a measurement and diagnostic system is currently under development at Gdansk University of Technology (GUT). Appropriate measurements and simulations of the special transformer system were performed to verify the proposed diagnostic method. In order to take into account the nonlinearity and hysteresis of the magnetic yoke, a novel mathematical model of the transformer was developed. A special test bench was constructed to emulate the inter-turn faults within transformer windings