Metamorphism of bearing lubricants is caused by current damage

The metamorphism of bearing lubricants is a typical manifestation of bearing damage caused by current. The protection current of the DC resistance has a different effect. The electrically eroded bearing has different damage manifestations from the bearing subjected to DC erosion. In DC electrical equipment, the bearing acts as an ohmic resistor. The aluminum oxide layer of the bearing is equivalent to an insulator. The insulation resistance value is equivalent to the DC resistance R, the size is 50MQ, and the breakdown voltage is 1000V. Therefore, the bearing can effectively function as an insulation.

In AC motors, especially for pulse width modulated inverters, the alumina coating of the bearing does not provide insulation. In this case, a set of "insulating garments" should be made, which package the entire bearing, including the inner and outer rings of the bearing, the rolling elements, the cage, the lubricant, and the contact points and raceways in the bearing.

In the direct current motor of the locomotive, the electrical erosion of the bearing is mainly represented by pits. The diameter of each pit is between about 0.1 and 0.5 mm and can be seen with the naked eye. The netting is a kind of colored plaque composed of a plurality of gray lines perpendicular to the raceway, which is formed by rolling down the rolling metal to form a damage on the raceway. This is not a direct damage to the bearing caused by high frequency current, but an indirect damage.

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