Development of a virtual hardware temperature observer for frequency-controlled asynchronous electric motors

Abstract

One of the most common types of AC electric machines are asynchronous electric motors. Because of their simple and reliable design, they are used in many industries. In this paper, the object of research is an asynchronous electric motor with a short-circuited rotor. To ensure the normal operation of an asynchronous electric motor, the heating temperature of its active parts should not exceed the maximum permissible values, which are determined by the corresponding class of heat resistance of the insulation system used in the electric motor. In asynchronous electric motors, the stator winding is the most thermally vulnerable node, which is the first to fail when the temperature of the electric motor increases. Thermal protection devices protect an asynchronous electric motor from emergency operating modes accompanied by an unacceptable excess of the temperature of their windings. In order to build an indirect system of protection against overheating of the stator windings, a temperature observer has been developed using already available signals in a frequency-controlled electric drive. Simulation studies were performed in Matlab/Simulink application software packages. Simulation studies were carried out on the basis of asynchronous electric motors of the 4A series with a capacity of 30, 75 and 110 kW in the temperature range from 20 °C to 250 °C. As a result of the research, it was found that the error of indirect calculation of the temperature of electric motors, taking into account the correction factor, does not exceed 1 %. The proposed temperature observer can be used to build protections for asynchronous electric drives

Indirect temperature protection of an asynchronous generator by stator winding resistance measurement with superimposition of high-frequency pulse signals

“…The most widely used in the tasks of analyzing various modes of operation of SCR AG are classical electromechanical models in the state space in a fixed coordinate system α-β, where the stator current vector and the rotor flow coupling vector are taken as state variables [10,11], which has the following form:…”