Mechanical and Electrical Faults and Causes in Case of Electrical Machines

Sr. No.

Fault

Reasons

Remedial measures

1

Bent shape

Drawback in shaft coupling machine to machine or machine to load
shaft. Concentric coupling very tight fitting of nuts and bolts having no
flexibility. Wrong and crowed storage of machine one over the other. Damages
in transport.

Due care during storage, transportation must be taken. Loosening
properly the nut bolts fittings. Do the alignment of coupling and adjust nut
bolt moving it till feel free movement of two coupled shafts.

2

Snapped binding

Sometimes centrifugal force developed on the armature winding is
greater.

Take the proper measures.

3

Trouble in bearning

Lubrications, greasing, maintenance scheduled not fooled. Machine
load coupling miss alignment. 

Load the machine properly. Check coupling. Replace bearing. Stop
machine if vibrations are excessive.

4

Mismatching of brush and brush holders on slip rings.

If holders are not proper as per the brush size and spring tension is
loose then vibrations are created.

Adjust properly.

5

Transformer

( i ) Brushing developed cracks

Change in atmospheric conditions too cold, too hot, heavy rains
affect the brushing. Electrostatic stress may be cause cracks on burning.
This may also be due to pressure of connecting rod used for connecting
supply.

Maintenance schedules must be followed for clearing dust, dirt.
Connections of supply line must observed.  

( ii ) Tap changer not working properly

( iii )Damaged gaskets

Contact might have been damaged due arcs developed when tap changer
is used frequently on load. Gasket makes the air tight seal of tank
containing oil in full level. Atmospheric conditions and reaction of oil with
gasket material damages the gasket.

During breakdown maintenance, clean the contacts, remove carbon.

Replacement of gasket periodically.

Sr. No.

Fault

Reasons

Remedial measures

1

wrong electric connections

Field winding connections may be wrong. Field-Armature winding
connection might be wrong. 3-phase motor phase sequence connection R-Y-B may
be wrong.

Check the connection. Check direction of rotation. Interchange
connection for working.

2

Contact, connections opening.

Dry soldering, improper and loose soldering of joints. Melting of
contacts. Break due to opening of soldering.

Resolder the joint etc. Clean the contacts. Dry soldered joints be
opened are again to be joint.

3

Damaged insulation

Over voltage storage long running, over loading, entry of moisture.

Dry the insulation. Check the voltage, reduce load. Stop the machine
intermittently for some time.

4

Commutator darkening, burning.

Due to dirt / Dust accumulation offering low resistance path to the flow
of current from positive brush to negative brush. Improper brush tension on
commutator or on the slip-rings. Shape less brushes creating gap between
brush and commutator surface / slip-ring surface.

Clean the commutator. Adjust and check brush tension. Replace shape
less brushes.