Ques. How does moisture in the armature coils affect the armature?
Ans. The effect of this fault being to practically short circuit the armature, a heating of the latter results. In bad cases, steam or vapor is given off.
Ques. What is the effect of short circuits in the armature?
Ans. It produces overheating.
Ques. What trouble is likely to occur when the armature is not centered in the armature chamber?
Ans. A heating of the bearings is liable to be occasioned through the attractive forces developed by the center of the armature core not being parallel with the centre of the armature chamber or bore, or through the core being nearer one pole piece than the other.
This may result from unequal wearing of the bearings, and therefore the bearings should either be relined or the bolt holes of the bearings readjusted, or the bearings packed up until the armature is correctly centered.
Ques. What happens in case of breaks in the armature coils?
Ans. This fault results in local heating of the armature, for the reason that resistance is interposed in the path of the current at the fracture. It always results in sparking at the brushes, and the heating being confined to the neighborhood of the break.
Ques. What are the effects of operation above the rated voltage and below normal speed?