Embedded resistor

for railway applications

Mersen proposes a range of On-board resistance. Those resistances have the function to artificially increase the resistance of the connection point in order to “push” the current through the ERCU. When the train is stopped, the resistance value of the ground brush is superior at the value of the bearing so the current flows through it but when the rotation starts (train in movement speed ≥30 Km/h), the voltage value of the ground brush is inferior to the one of the bearing and the ERCU starts to shunt the current. This is why you must install a resistance to increase the resistance value in order to keep the current flow through the ERCU even when the train is stopped. Bearing deterioration due to current: Spark erosion To cross a bearing, the current has to get through the interfaces between the rollers and the rolling surfaces. Then it has to get through the various insulating barriers formed by layers of metal oxides on the surface and by the lubricant.  So the current "breaks through" these dielectric surroundings in a series of small electrical arcs, a phenomenon that is sometimes called sparking. This causes: •  Brief heating in very limited places of the metal making up the rolling surfaces and the rollers. •  Brief changes in the metallurgical structure, resulting in "crescents of white martensite". •  Those crescents then gradually lose cohesion and flaking develops, increasing over time. The particles of metal that come loose during this phase will make the rollers slide on their rolling surfaces and impact them in places.