Kostenko A. Variable-frequency electric drive with the compensation of impact of stator windings asymmetry in induction motor

The object of research - the process of energy conversion in variable frequency electric drive with scalar control; The aim is to improve the efficiency of variable frequency electric drive with scalar control with asymmetric induction motor by evaluating the energy performance and compensation of asymmetry of stator windings on the modes of its work; research methods are based on the theoretical foundations of electrical engineering, Fourier theory, methods of instantaneous power theory, numerical methods for solving equations and systems, mathematical modeling and experimental research methods, experimental design theory, methods of self control voltage inverter; Theoretical results, was developed a method of indirect determination of shaft power and energy characteristics of variable frequency electric drive with induction motors, which, unlike known, allows without inference into engine from the technological process and with minimal information on the parameters of the equivalent circuit to evaluate the effectiveness of alternative current electric drive in conditions of engine unbalance and change the mode of its operation on the basis of the measured signal of instantaneous values of stator current and voltage; was developed a method of compensation of induction motor stator asymmetry within the variable frequency electric drive with scalar control, which, unlike the existing ones, without hardware changes in the power range of electric drive through the use of cross-vector instantaneous power theory and adaptive voltage regulator compensates the variable components of consumption power or the electromagnetic torque of the motor, reduce the unbalance currents and thermal overload of individual phases of the stator and the power semiconductor keys of the inverter; for the first time the method of calculation of the optimum life of the induction motor from the electric drives according to the criterion of minimum costs, the use of which would reduce industry costs associated with the operation of induction motors with impaired energy characteristics by conducting timely capital and current repairs or replacements. Practical results – it was designed hardware and guidance of indirect methods of determining the energy characteristics of the variable-frequency electric drive based on instantaneous values of stator phase currents and voltages of induction motor that can be used without disconnecting the engine from the technological mechanism; the algorithm for calculating the optimal life of the induction motor according to the criterion of minimum costs; defined the relationship between the asymmetry of induction motor stator windings and the residual resource of motor isolation for the task of compensation of its impact; developed and recommended the structure, principles of implementation, algorithmic software of system for unbalance compensation of stator windings by means of the variable frequency electric drive with scalar control.