I don't know for sure, but normal useage of the term active and inactive would suggest that the active bearing carries the load during normal operation, the inactive only during special conditions.
For example large vertical motor. Typically Kingsbury bearing is continuously carrying the weight and downthrust. It would be the active bearing.
During momentary upthrust, the rotor is free to move some distance at which point it is stopped by some other bearing. Sometimes this function is performed by movement of a lower ball bearing over a limited range. Sometimes a separate upthrust bearing above the upper bearing. Either way the thrust bearing taking momentary thrust would seem to be inactive thrust bearing.
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I think the terms are applying
to static and dynamic.
Static means at rest or inactive
ie not rotating. Typical would
be a crane picking up a load and
not rotating or at rest. Dynamic
would be the load condition while
rotating.
electricpete is right, as always The in-cative thrust bearing is the bearing not normally seeing the load. On Kingsbury bearings this bearing quite often sees the most wear.
On vertical motors many Hi thrust applications use a large bearing for down thrust (7320 and will use a smaller 7220 for the up thrust). The different sizing is used as the normal up thrust is momentary only and of less force.
