Satisfactory motor bearing service life: a review of often overlooked design considerations

There has been a steady increase in motor bearing life (i.e. L/sub 10/) requirements, often at elevated loading conditions. As a consequence of this requirement, motors are being designed with bearings which can accommodate these increased loads and longer life requirements. All too often, these same motors are applied in standard, or even lightly loaded conditions. Under lightly loaded conditions, there frequently exists a situation in which there is insufficient loading present to keep the bearing from skidding, and eventually failing. In these instances, the bearing never achieves its theoretical L/sub 10/ life, as it is limited by its actual shortened service life. This paper describes the minimum load requirements as they effect the actual service life, and the effects of bearing type, bearing size, lubricant selection, motor speed, and momentary light load operation.<>