Page 232 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

• The importance of the motor/generator in the production
• The duty cycle of the machine
• The age of the machine
• The earlier history of the machine

• The environment in which the machine operates
• The recommendations of the manufacturer.
Recommended maintenance schedule for machines: While carrying out routine periodical maintenance, an
electrician will make full use of his senses to diagnose and locate problems in Power machines. The sense of
smell directs attention to burning insulation: the sense of feel detects excessive heating in winding or bearing; the
sense of hearing detects excessive noise, speed or vibration and the sense of sight detects excessive sparking
and many other mechanical faults.
Sensory impressions must also be supplemented by various testing procedures to localize the trouble. A thorough
understanding of Power principles and the efficient use of test equipment are important to an electrician during
this phase of operation.
The following maintenance schedule is recommended for DC machines.

1 Daily maintenance
• Examine visually earth connections and machine leads.
• Check the sparking at the commutator.
• Check the motor windings for overheating. (The permissible maximum temperature is near about that
which can be comfortably felt by hand.)
• Examine the control equipment.
• In the case of oil-ring lubricated machines
a) examine the bearings to see that the oil rings are working

b) note the temperature of the bearings
c) add oil, if necessary
d) check end play.
• Check for unusual noise at the machine while running.
2 Weekly maintenance

• Examine the commutator and brushes.
• Check belt tension. In cases where this is excessive it should immediately be reduced. In the case of
sleeve-bearing machines, the air gap between the rotor and stator should be checked.
• Blow out air through the windings of protected type machines situated in dusty locations.

• Examine the starting equipment for burnt contacts where machine is started and stopped frequently.
• Examine oil in the case of oil-ring lubricated bearings for contamination by dust, grit, etc.(This can be
roughly judged from the colour of the oil.)

• Check foundation bolts and other fasteners.
3 Monthly maintenance
• Overhaul controllers.
• Inspect and clean the oil circuit breakers.

• Renew the oil in high- speed bearings which are in damp and dusty locations.
• Wipe the brush-holders and check the bedding of brushes of DC machines.
• Test the insulation of windings.

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CITS : Power - Electrician & Wireman - Lesson 93-100 CITS : Power - Electrician & Wireman - Lesson 93-100