Lohmatov A. Determining and preventing of fault modes in variable-frequency asynchronous electric drives

The dissertation is devoted to research of electromagnetic processes, problems of identification and automatic control in emergency operation for the asynchronous electric drive on the basis of the voltage source inverter (VSI) with pulse-width modulation (PWM). For performance of researches of electromagnetic processes at emergency operation asynchronous electric drive with VSI-PWM mathematical description and simulation model of electric drive are developed, by which discrete properties and nonsinusoidal wave form of output voltages (currents) of the inverter, nonlinearity of a curve of magnetization of the motor are considered. With operational image, generalized vectors, equivalent sources techniques electromagnetic processes in asynchronous electric drive with VSI-PWM are calculated at fault modes: internal short-circuit in the inverter, a failure and restoration of grid voltage, open-phase modes of the inverter caused by disappearance of one or several control pulses from power switches. Based onthe analysis of these electromagnetic processes analytical dependences for their engineering calculation are received, algorithms of identification of approach of fault mode and effective algorithms of automatic control asynchronous electric drive with VSI-PWM are offered at the fault modes, preventing failures of power switches of the electric drive in operation.