Study of electromechanical and thermal transients during starting of induction motors

Abstract

This article presents the results of analytical studies of electromechanical and thermal transients during starting of induction motor with cage rotor in conditions of low voltage. The aim of the research is improving the operational reliability of induction motor with cage rotor in conditions of low voltage by development of technical devices for diagnostics based on theoretical foundations of electromechanical and thermal transients at starting. As a result of the research the theory of transient electromechanical and thermal processes in induction motor with cage rotor in conditions of low voltage is found a further development. For the first time it is proposed the starting mode evaluation parameter of system "induction motor – working machine" – the ratio of the moment of inertia of the system to the nominal moment of induction motor. For the first time it is grounded the parameter of diagnosing transient thermal processes at starting of induction motor in conditions of low voltage – extra thermal insulation depreciation in the period after starting. For the first time it is grounded the criterion of extra thermal insulation depreciation in the period after starting – squared power momentum of inrush current, which can be taken as a diagnostic parameter. Investigation of thermal insulation depreciation showed that the thermal transient at the start is adiabatic. Main thermal insulation depreciation is accounted for period after starting. The dependence of extra thermal insulation depreciation on squared momentum of inrush current allows selecting set point value of squared power momentum of inrush current of proposed device, which will facilitate the starting mode of the motor.