Comprehensive assessment of the quality of laminated core of electrical machines by the high-frequency induction-vibration method

Abstract

In this work, the problem of assessing the quality of active parts of electric machines, in particular charged magnetic conductors, is considered. The essential diagnostic indicators of the actual state of the recruitment core were determined, namely specific losses during remagnetization and weakening of package pressing, which are associated with increased losses, decreased efficiency, violation of the thermal regime, etc. induction-measuring module for determining the level of inter-sheet insulation breakdown and the growth of losses in the core. It is recommended when loosening for small-sized magnetic conductors, impregnation of the weakened area with adhesive varnish and subsequent drying with a compressed core. Also, for cores of a small diameter, between the pressure washer and the extreme sheets of the core, drive textolite wedges every 2...4 teeth. When the pressing of the cores of large electric machines, in which the pressing is carried out by tension pins, is weakened, the pins are tightened. A two-dimensional field mathematical model of a charged magnetic core package was developed in order to estimate the distribution of the electromagnetic field and eddy currents and losses at different frequencies from 50 Hz to 10 kHz. It is proposed to use the analysis of the transient process when the magnetic flux changes in the magnetic circuit. To simplify the measuring scheme, it is proposed to use the process of switching the current in the excitation winding. With the help of the developed model, the calculation of transient modes was carried out on the example of the studied magnetic circuit. As an object of research, a mock-up of a stacked magnetic core was used, which is a set package of magnetic steel sheets used in magnetic cores of dry transformers of small and medium power. In order to combine the two methods, an installation was developed that allows checking the quality of pressing and the quality of inter-sheet insulation at the same time.