Rolling bearings in electric motors and generators

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1 Rolling bearings in electric machines
Design requirements
Dimensions
In most cases, power output determines
shaft size, and shaft size determines
the bore diameter of the bearings.
In recent years, however, the
tendency has been to use bearings
with smaller cross sections because
they require less space.
Loads
In order to select the best bearing
for a particular application, all loads
should be considered and not just
the weights involved and the forces
derived from the power transmitted.
Be sure to include additional forces
like the magnetic pull resulting from
unsymmetrical air gaps, dynamic
forces due to inaccurate adjustment,
out-of-balance situations, pitch errors
in gears, as well as any thrust loads.
Heavy loads are generally carried by
roller bearings, where lighter loads are
carried by ball bearings. Drive forces
are considered only when belts or gears
are utilized. Loads can be radial, axial
or a combination of the two. Certain
bearings, such as cylindrical roller bearings,
usually carry radial loads only;
where other bearings, such as angular
contact ball bearings, are more suited
for axial loads.
In order to provide satisfactory
operation, ball or roller bearings must
always be subjected to a given minimum
load. Please refer to the relevant
bearing type in the table section of the
SKF General Catalogue.
Fig
1
Design
requirements
Bearing
section and
calculation
Operating
conditions
Parameters that
have to be taken
into consideration
when designing an
electric machine
N = Non-drive end
D = Drive end
Manufacturing
Maintenance
10
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