Reasons for Developing Electrical and Magnetic Fault

Sr. No.

Fault

Reasons

Remedial measures

1

Wrong electric connections

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

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

2

Contact, connections opening.

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

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

3

Damaged Insulation

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

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

4

Commutator darkning, 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 sliprings. 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.

Sr.no.

Fault

Reasons

Remedial
measures

1

Mialsalignment of poles.

Due to mechanical injuries, blows, wrong storage of machine sometimes
distance between poles is disturbed. Pole fitting with nut-bolts may not be
proper. This disturbs flux distribution.

Necessary alignment should be done. Nut-bolt fitting should be
proper.

2

Loose poles.

Due to excessive vibration created by abnormal speed, loose
foundation fittings. The ples becomes w.r.t yoke. This distribution.

Steps be taken to correct the position and make tight fitting of
poles with yoke.

3

Non-uniform air-gap

If rotating path is not true then it create a non uniform air-gap.

Tighten the core stampings. adjust the voltage to its normal voltage,
load the machine properly avoiding  overloads.

4

Abnormal heating of core

Magnetic looses increase if there is gap between stamping of core,
core insulation damaged, over heating of insulation due to overload or
excessive voltage. This result in non-uniform flux distribution.

Tighten the core stampings. Adjust the voltage to its normal voltage,
load the machine properly avoiding overload.

5

Warped and dented core and burns.

At some spots the insulation on the core is burnt, causes sharp rise
of losses in core.

Necessary repairs rewarnishing core. Replacing same stampings.