Analysis of the thermal state of the electromagnetic mill inductor with oil cooling in stationary operation modes

Abstract

Introduction. An electromagnetic mill (EMM) for the technological processing of various substances, which is based on the stator of a three-phase induction motor, is being studied. The stator winding has an increased current density, so the mill is provided with a system of forced cooling with transformer oil. Problem. Currently, there are no works on the thermal state calculation of the EMM with the given design and oil cooling. Therefore, the study of such EMMs thermal state is relevant, as it will contribute to increasing the reliability and efficiency of their work. Goal. Formation of a mathematical model of the thermal state of the electromagnetic mill inductor and the analysis of its heating in stationary modes of operation with cooling by transformer oil. Methodology. The problem of calculating the thermal state, namely the temperature distribution in the main parts of the electromagnetic mill, is solved by the equivalent thermal resistance circuit method. The design of the EMM is provided in a sufficiently complete volume, and on this basis, a corresponding equivalent thermal replacement circuit is formed, which is supplemented by an equivalent hydraulic circuit of oil passageways. An explanation is provided for the composition and solution of the equations algebraic system that describes the distribution of temperatures by the constituent elements of the EMM. Results. The thermal calculation results of the electromagnetic mill showed that the maximum heating temperature is much lower than the allowable one for the selected insulation class. According to the hydraulic scheme, the necessary oil consumption, its average speed and the corresponding pressure at the inlet of the intake pipe are determined, which are at an acceptable level. It is noted that the rather moderate temperature state of the inductor and the hydraulic parameters of the oil path are facilitated by such innovations in the design of the EMM as the loop double layer short chorded winding and axial ventilation channels in the stator core. Originality. Now EMM thermal equivalent circuits with air cooling only have been presented. Therefore, the developed thermal circuit of the oil-cooled inductor is new and makes it possible to evaluate the operating modes of the EMM. Practical value. The proposed technical solutions can be recommended for practical implementation in other EMMs. Taking into account the identified reserves of the EMM temperature state, a forecast was made regarding the transition from its oil cooling to air cooling. But the use of air cooling requires a change in the design of the EMM.