Rotordynamic Influence of a Spider Mounted on Shaft with Interference Fit in an Electric Machine Rotor

In some electrical machines, the symmetrical ventilation system design allows airflow axially from the two end sides to the rotor core. Once the rotor core plates are mounted on shaft is necessary to weld ribs, steel beams radially disposed on shaft, to create channels for the airflow to come in between the shaft and rotor plates. In case of shaft material with a poor weldability, instead of welded ribs, it must be used a type of shaft runner mounted with interference on the shaft. Lately, this shaft runner would support the rotating electric machine rotor core. On this concept, the airflow goes through the welded beams on the shaft runner, considering the design and manufacturing with a steel that has good weldability. The interference with which the shaft runner was mounted, affects its dynamic behavior, because when the rotating electric machine runs, the centrifugal forces on its rotor tends to relieve the pressure in the fit between the runner and the shaft. This relief may generates areas in which there will not be contact, which consequently changes the rotor dynamic behavior. This paper proposes a specific calculation routine, based on finite element analysis via ANSYS^®, to study the influence of interference fit for the shaft runner on the rotordynamic behavior of the machine.