Failure Analysis of Graphite Bearing in Electromotor

When an electromotor was tested after repair, the indicator light couldn't work effectively. It was found that the yellow line and red line were broken. And then it was found that the temperature fuse in the C phase circuit had been melted and broken and the graphic bearing had fractured. To find out the failure cause of the graphite bearing, macro and micro observation, metallographic examination and hardness test were carried out. The results show that the fracture mode of the graphite bearing is overload fracture after heat damage. The heat damage was caused by the friction between the graphite bearing end surface and the rotor end surface. Accordingly, it is suggested that the installation clearance between graphite bearing end surface and rotor end surface should be controlled to reduce friction and heat damage.