Abstract
The study presents the results of the analysis of applied methods and computer programs for processing electrical signals that change in function of time. A methodology, hardware and software have been developed for testing the quality of the stator steel of asynchronous machines with an extracted rotor during their overhaul or modernization at electrical repair enterprises. The test method provides for assessing the quality of the stator steel by magnetizing it with a reference voltage proportional to the design magnetic induction in the back of the stator steel, recording oscillograms of magnetizing voltage and current and power losses in the steel. The recorded oscillograms of voltage and current are digitized. A software tool has been developed that allows analyzing of digitized signals according to the following five criteria: phase shift of voltage and current equal to the difference between the initial voltage phases and the initial phase of the current determined by their maximum values; an increment of the magnetizing current equal to the difference between the maximum value of the current and the current at a voltage phase equal to 90⁰; active power losses in the stator steel; shift of the initial phases of voltage and magnetizing current; harmonic composition of voltage and magnetizing current. Logical equations have been developed, the arguments of which are the listed criteria, which allow making decisions about the quality of the stator steel, whether the steel is good, satisfactory, or bad, without human intervention. The paper contains an electrical diagram of the hardware of the device for testing stator steel; the detailed algorithm for processing digitized signals; the results of experimental studies of the stator steel of an asynchronous motor of the AI225M8Y3 type, with a power of 30 kW and the rotational speed of 735 rpm. The technique, hardware and software complex make it possible to assess the quality of the stator steel of each engine being repaired, to repair the engines with minimal labor and material costs. The development is recommended for specialists of electrical repair enterprises.
Keywords
Asynchronous motor, stator steel, test procedure, oscillograms, hardware complex, computer program, steel quality criteria.
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