Join Date: Dec 2019
Location: West Central Indiana
There's a failure mode that, while rare on single phase motors, I've run into twice on dust collector motors.
Dust collectors are often subject to fairly short on-off cycles and at the same time have a high inertia load that prolongs the duration of the start current. This can cause excessive heating of the rotor conductors, softening the Aluminum they're made of. These conductors are connected by a shorting rings that are also Aluminum, cast into the rotor at the same time as the bars. There's a stress riser at the join of the two that can fail when the Aluminum is weakened by high temperature. When the connection to a bar is opened it no longer conducts current. That missing current has to be made up by increased current in the other bars. That causes more heating of those bars on subsequent starts leading to a cascade of failing joints.
This is especially rare on single phase motors because, under these conditions, the start capacitor usually fails long before the rotor does.
When you changed the bearings did you notice anything that looked odd on the rotor? Were there any loose pieces of Aluminum inside the motor housing?
Like I said, that's a rare failure mode. If it it were my motor I think I would want to convince myself that the centrifugal switch is actually working properly. Maybe attach a meter to the start capacitor terminals and make sure there's a solid voltage there when the motor is switched on.