Abstract
In the case of large induction motors, it is very important to quickly and safely identify the onset of failure. In that way one should take appropriate corrective measures to prevent significant damage. In this paper, the comparative diagnostics between two high-voltage large induction motors using the specific proposed waveform analysis of current during the direct-on-line start is presented. Using the previously recorded signals, a rotating current vector amplitudes for both machines are determined. Their shapes are analysed and the presence of the initial 100Hz stator current component, indicating the existence of a rotor failure, is observed.
Highlights
ModelovanjePosmatra se simetričan trofazni sistem struja prikazan na slici 1.
Projekcija vrhova vektora struja ia i ib predstavlja obrtni vektor struje I(t).
On je postavljen u odnosu na struju faze “a” pod uglom θ = ωt + θo.
Summary
Posmatra se simetričan trofazni sistem struja prikazan na slici 1. Projekcija vrhova vektora struja ia i ib predstavlja obrtni vektor struje I(t). On je postavljen u odnosu na struju faze “a” pod uglom θ = ωt + θo. Struje ia i ib se mogu predstaviti pomoću relacija (1) i (2). Uvršćavanjem ovih jednakosti u relaciju dolazi se do izraza (4) koji predstavlja trenutnu vrednost amplitude obrtnog vektora struje I. Za neku konkretnu vrednost ia Ix sin( t) i ib Ix sin t 120 dobija se da je I = Ix, odnosno obrtni vektor struje je jednak konstanti. U Simulinku je napravljena blok šema (slika 2) za simulaciju obrtnog vektora struje. Na slici 3 prvi dijagram predstavlja struju ia, drugi struju ib, a treći amplitudu obrtnog vektora struje I(t). Struje faze “a”, “b” i amplituda obrtnog vektora u vremenu, u slučaju simetričnog sistema; ukupno vreme simulacije je 60 ms
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