Thermal modes of the automated electric drive system during burning under load

Abstract

Purpose. Conducting experimental studies of temperature regimes of an induction motor during start-up on a laboratory complex. Obtaining real characteristics of the heating process during the start of the start, assessing its impact on the insulation state of the induction motor, confirming the adequacy of the indirect method of determining the heating temperature of the induction motor windings during the formation of the cyclic starting torque during the start.

Methodology. To solve these problems, we used mathematical modeling based on the first mathematical expressions that calculate the temperature of the stator winding during start-up, taking into account the influence of the frequency of the supply voltage on the parameters of the induction motor. Physical modeling on the developed laboratory stand of modes of movement on fixing of temperature during each stage of experiment for confirmation of theoretical researches of movement at pulse character of the starting moment.

Findings. The use of different methods of constructing equivalent thermal circuits (ETS) to calculate the temperature of an induction motor requires significant resource consumption, which is unprofitable when the rotor of the machine is stationary as in the case of failure. Using the method of determining losses in steel in the deep saturation mode, the mathematical dependences of the calculation of the temperature regime during the algorithm, taking into account the change in the properties of the stator winding during heating, calculated the allowable current overload parameters taking into account the allowable heating of stator windings. The paper obtains mathematical dependences for calculating the temperature regimes of the stator windings during the formation of the cyclic starting torque for the movement, taking into account the change of the initial conditions of the movement for each cycle and the change in the properties of the stator windings during heating. The developed laboratory complex allows to carry out research of temperature modes of a stator winding at movement of the induction motor with the braked rotor, at assignment of various values ​​of amplitude and frequency of supply voltage. The results of research indicate that the mathematical dependences derived in the work allow to control the heating temperature by the analytical method. Analysis of the modes of operation of the induction motor during the execution of the movement confirmed the need to control the temperature of the stator windings to prevent accidents. In general, when starting with a step-by-step supply of low frequency supply voltage to obtain increased starting torque, the heating of the stator windings is slower compared to heating during prolonged operation of an induction motor with a braked rotor, which allows multiple attempts to move at low frequency. nutrition.

Originality. For the first time, mathematical dependences for calculating the temperature of stator windings during start-up with a braked rotor of an asynchronous machine are obtained and experimentally confirmed, which take into account the change in stator winding properties during heating and the influence of supply voltage frequency.

Practical value.  For the first time, an indirect method of controlling the heating temperature of the stator windings of an asynchronous machine during start-up is proposed to prevent emergencies on process equipment that is started under load.