Karl Townsend wrote:


I can see 2 effects of higher that rated RPM: centrifugal forces on the
rotor windings (do 3 ph motors have rotor windings?)
Kind of. Typical induction motors have "shorting
bars", which are shaped copper bars that are
shoved into the slots in the rotor laminations and
capped with copper plates at each end. The bars
are welded to the plates.

There are wound-rotor induction motors that are
used with commutators and brushes for slow
starting of large inertial loads like blowers and
carousels. Some have spring-loaded "bracelets"
that expand by centrifugal force to short the
commutator when the motor is up to speed.

Jon