Heating and protection the windings of auxiliary machines of the AC electric multiple-unit trains at short-time overloads

Abstract

Statistical analysis shows that about 20% of the auxiliary machines of AC electric multiple-unit trains (compressor, oil pump for cooling traction transformer, the motors of ventilation aggregates) are fails every year. Obviously, that the issue of increasing the reliability of auxiliary machines of AC trains ER9M series is now urgent. The main cause of the failure of these machines is the insulation damage of the stator winding of the motor. On the trains ER9M series use the general purpose industrial induction motors with squirrel-cage rotor of AOM type and the similar to them, more modern AIR type. The fact of the failure of the engine shows that the insulation of the stator winding overheating above the allowable temperature. The reason of that becomes the fact that the engine in a mode of real operation works with transient overloads. These overloads caused by the fact that the engines are work in a much more difficult conditions than in industry, to which can be attributed the significant variations of the supply voltage, which are characteristic of the AC rolling stock, operation at low air temperatures and so on. In this paper it is set the task to identify the maximum permissible duration of transient overloads, during which the motor insulation will not be overheated above the allowable temperature. An engineering method for determining these characteristics is proposed. Experimentally obtained the time-current characteristics of the electrothermal relays. The comparison of the obtained analytical dependence with the experimentally measured characteristics of real thermal protection on the basis of the thermal relay TRT-115 is done. Formulated recommendations to increase the reliability of the thermal protection of asynchronous motors with squirrel-cage rotor, which are work in transient overloads modes.