A main argument for configuring an EMU with few driven axles is to keep the total number of components as low as possible. This is, in turn, attractive from both cost and reliability point of view.
With fewer motors generating the tractive effort, each motor needs to be more powerful. These motors are typically forced cooled from an external fan, an arrangement that requires a high degree of integration into the car body. Each motor must be perfectly tailored and optimized from a system perspective, rather than being mechanically optimized individually.
This propulsion type typically requires traction motors with high torque density. ABB’s welded stator frame motor utilizes the given space envelop to the maximum, providing the optimum performance-space ratio for trains with few driven axles.