I believe you're referring to the rotor end ring. That is the object directly behind the bearing. The benefit of end rings is that they connect all the windings together so that current can flow as opposed to building up and arcing. Thanks for the comment! Hope this helps.
@@fee2044 Bearing covers come in two parts that are bolted together in order to enclose the bearing and prevent foreign particles from entering and causing fouling. The bearing cover only needs to be removed if damaged or worn and since this one was fine it was not removed.