Traction motors of railway vehicles

In Traction Motors like railcars & metro cars, deep groove ball bearings and cylindrical roler bearings with insulation coating are used to prevent damager due to current passage. For example: 6313/C3VL0241 & NU320EM/C4VL0241,  6309M/C4VL0241 & NU212ECM/C4VA3091,  6016M/C3VL0241 & NU210EM/C3VA3091