Marenych O. Reliability improvement of individual railway rolling stock contactors

The thesis deals with the reliability improvement of individual railway rolling stock contactors by ensuring the determined value of force safety factor at the critical air gap, in order to secure complete switching of a contactor, and taking into account the value of short-time thermal current, while choosing contactors for electrical circuits. Analysis of statistic data has shown that for 27% of traction electromagnetic contactors (TEC) the correlation of traction and counteracting characteristics at the minimal voltage in control circuits may not fulfil conditions of contactor complete switching (when an armature is fully attracted to a core). It was shown that the value of short-time thermal current is not specified in the list of TEC technical characteristics. To calculate dispersion of traction and counteracting characteristics an analytical expression has been developed; to increase accuracy of the calculation a new method has been proposed. Recommendations for choosing the rational value of force safety factor at the critical air gap have been developed in order to secure complete switching of contactors at the minimal voltage in control circuits of rolling stock. A dependence between probability of contactor complete switching and the critical air gap (in relative units) was found using a classical model of parametric reliability. It was proved that the short-time thermal current should be added to the list of parameters which characterize rolling stock contactors at the present time.