Gusarow A. The protection of the asynchronous device by means of modeling the current thermal state by thermal detector correction.

The object of research is the thermal processes under steady-state and transient duties of AD operation in the course of the thermal overloads of low and high growth. The purpose is the improvement of the temperature protection of the low voltage asynchronous electric devices at the expense of the control function realization of the current temperature state and signaling of processes providing the excess of the accepted heating of both stator and rotor windings. The tasks of the given paper are solved on the basis of the method of the equivalent thermal circuits, the method of the finite differences, the method of the equivalent thermal losses - for the mathematical representation of the thermal processes in the AD; the theory of the electromagnetic field - for studying the influence of the skin-effect on heating of the short-circuited rotor bar; the methods of the analytical solution of the system of the linear differential equation and methods of the matrix algebra - for the mathematical modeling of processes. The research paper develops the mathematical model of the thermal state of the low-voltage asynchronous device for its temperature protection under the thermal overload of low and high growth and non-standard operating conditions, which is differ from the standard model by using the nodes: for thermal detector the nodes are used in the front stator winding and for the rotor winding the nodes are used by taking the skin-effect into account. For the first time, with the help of the thermal model of the rotor winding the paper researches the skin-effect influence or the distribution of the temperature gradient in the rotor slot. The above influence causes the time variations of the highest temperature along the slot depth. For the first time, with the purpose of use in the temperature relay the obtained results of the temperature gradient distribution along the rotor slot depth by taken the skin-effect into account, the author presented the analytical solution of the field task of penetration of the plane electromagnetic wave into the rotor rod. For the first time the paper develops the temperature protection which helps to make corrections of the modeling results on the basis of the analysis of the difference between the factual and estimated temperatures of the thermal detector as well as to indicate unexpected deviations which take place within the electrical drive or to switch off the overheated electrical engine. The results of the research in the form of recommendation and methods as well as the algorithm and programs of the microcontroller of the temperature relay are used by the Ukrainich research design and construction technological institute of the explosion-proof and mining electrical equipment of the pilot production (the city of Donetsk) to develop the combined systems of the thermal protection of the asynchronous low-voltage explosion-proof engine of the coal flight conveyer of the type 2ЭДКОФ250М4 whose power is 55 kW. The results of the paper are also used by the students studing at the Donetsk National Technical Unsversity.