A methodology for random fatigue validation of a railway vehicle transformer according to the standard EN 61373

Electrical equipment mounted on trains are subjected to random loading and shocks in transversal, vertical and longitudinal directions. Customers often requires tests on shaker table according to standard EN61373. This standard defines loads spectrum and pulse shape for tests. Structure will respond to random and shock loads with its own dynamic increasing the stress level. Until now calculation were done according to EN12663 which defines equivalent static loads for shocks and vibrations. Therefore structure dynamic was totally neglected. If structure natural frequencies are within the frequency the load spectrum achieve its maximum (it happens if anti-vibrators are installed), the assumption of equivalent static loads is not valid any more. The risk is in that the machine will fail during tests. The purpose of the this work was the development of a methodology which allows the assessment of base material, bolted connections and weld seams of electrical equipment by means of FE simulation. FE simulation reproduce test conditions and the use of this methodology can replace tests on shaker table. The procedure is made of a sequence of steps. It starts with a general idealization of realty and with the model de-featuring that needs to be validate. After loads and boundary condition definition a transitions and random vibration analyses are carried out. Stresses and forces provided by analysis are used for bolted connections, base material and weld seams fatigue assessment. If the safety coefficient is high enough structure optimization can be easily done. This procedure has been successful applied on an inductor which has been subjected to shaker table.