Evaluation of the Permitted Number of Reduced-current Starts of the Powerful Induction Motor Drives on the Basis of the Oscillatory Component of Electromagnetic Torque

Transient processes arising in direct on line (DOL) start of powerful induction motor drives have a negative effect on the motor technical condition and the drive mechanism, reducing their operating life. One of the reasons of this effect is the electromagnetic torque oscillations of the motor when starting. Various non-equipollent in the limitation extent of the torque oscillatory component methods are used to facilitate the start conditions. In this paper integral quantitative criteria resulting from the analysis of the calculation oscillograph traces, making possible to estimate the oscillation degree of the electromagnetic torque and make a comparative analysis of the different start methods are introduced. A method of calculation the permissible number of starts per year, based on the estimation criteria of the torque oscillation degree was developed. The method allows to estimate the number of starts as for the chosen method, so for the combination of different methods.