STUDII DE TRANSFER DE CĂLDURĂ ÎN MAȘINI ELECTRICE UTILIZATE ÎN CONDIȚII DE FUNCȚIONARE SPECIALE

Abstract

"This paper aims to analyze the heat transfer of a DC limited angle torque motor, in special conditions, of space. Three-dimensional models will be used and two current values will be considered. As a working hypothesis, several variants will be numerically analyzed in which the boundary conditions will take into account different values of the emissivity of the motor surfaces varying in the range 0.2 ÷ 1. Inside the motor subassemblies the heat transfer will be done by conduction and between the motor and the environment by radiation. Using thermal modeling, it will be possible to determine the time in which the winding temperature reaches the maximum value allowed for the DC limited angle torque motor, in space conditions. The approached motor presents specific technical aspects (constructive and functional) and novelty in the field of torque motors with limited angle. These types of motors are recommended for applications where both volume and weight are critical requirements. The applications of DC-LATM are diverse: in the fields of aerospace, military technique, medical etc. For special applications (eg aerospace) a redundant motor solution is required [7]. The motor is designed for applications that require rotation over a certain angular range, (the working domain of this motor is 45 ÷ 135°). The space industry is a field of maximum interest from a scientific, economic and strategic point of view. Compared to other fields, its growth in recent years is extraordinary, as evidenced by the availability of telecommunications services. The requirements of the motor given by the application in which it is used including the environmental conditions in which the motor operates will determine the input data of the heat transfer problem. There are two categories of requirements that are equally important: general (mechanical, thermal, electrical) and environmental (stability to vacuum and radiation, resistance to AO - atomic oxygen) etc. Also, several aspects must be considered, such as: environmental effects (LEO - Low Earth Orbit or GEO - Geostationary Orbit), constraints applicable to materials (temperature, vacuum, thermal cycles, chemical - corrosion, galvanic compatibility, atomic oxygen , moisture absorption / desorption, fluid compatibility), if materials will degrade over time, the system in which the product will be integrated, interfaces [8]. The heat transfer analysis addressed in this paper establishes the DC-LATM behavior from a thermal point of view in space conditions."