Freight locomotives must be strong enough to start with full load at demanding inclines. Their speed is relatively low, up to 160 km/h, which allows for cost-effective axle-hung mounting of the traction motors.
To enable a high tractive effort, the motors have a high torque‑space ratio. Mounting the motor directly to the gearbox and wheel shaft (axle-hung) maximizes the available space for the motor and ensures a high torque-space ratio.
Given the strong forces and heavy loads, the bearings must be big enough to provide a high load carrying capacity. However, large bearings mean high peripheral speeds, calling for oil lubrication of the drive-side bearing.
ABB’s locomotive motors typically come with a welded stator frame to optimize the tight space envelope. Analyses let us optimize e.g. the trade-off between bearing and lubricant lifetime.