Bearing shield
Bearing shields are (mostly in electrical machines) the rear and front covers of the machine housing, which protect the inside of the machine against contact and hold the bearings of the shaft ends of the armature. They are fitted very precisely into the stator housing to ensure that the air gap between the stator and armature is as uniform as possible . When removing the end shields for repairs or maintenance work, the installation position must therefore be marked so that they can be reassembled in exactly the same position when reassembling.
The A-end shield designates the output side and usually has a fixed bearing, the B-end shield is the fan side and it is supported by a sliding seat to compensate for thermal expansion of the armature.