Best Practices for Maintenance Properly selected and installed motors can operate for many years with minimal maintenance. Nonetheless, regular care will extend their life and maximize their energy efficiency.

2. Electric motors convert electrical
energy into useful mechanical energy
by running electrical current through a
coil, resulting in the torque needed to
turn a shaft. Almost every major piece
of equipment in a commercial
building—boilers, chillers, air handlers,
pumps, and cooling towers, to name a
few—relies on electric motors.

3. As they run, motors can become less
efficient because of wear, breakdown of
lubricants, and misalignment. Good
motor-maintenance practice helps
avoid or postpone these problems. A
lack of maintenance can reduce a
motor’s energy efficiency and increase
unplanned downtime. Scheduled
maintenance is the best way to keep
the motors operating efficiently and
reliably.

6. A type of switch that
operates using the centrifugal
force created from the rotating
shaft. The centrifugal switch
activates and de-activates
depending on the speed of the
motor.

7. A device that
supports, guides, and
reduces the friction of
motion between fixed
and moving machine
parts.

8. On a piece of electric
equipment (such as a motor), a box
within which the leads from the
piece of equipment are connected
to the leads supplying the
equipment with power; usually
provided with a removable cover
plate for access.

9. A power supply is a
device that
supplies electric
power to an electrical
load.

10. is a self cooling electric motor.
Fan cooled motors feature an axial
fan attached to the rotor of the motor
(usually on the opposite end as the
output shaft) that spins with the
motor, providing increased airflow to
the motor's internal and external parts
which aids in cooling.

11. The fixed pulley in a
belt drive system that
receives energy from the
power source and transfers
it to the driven pulley.

12. In an electric motor the moving
part is the rotor which turns the
shaft to deliver the mechanical
power. The rotor usually has
conductors laid into it which carry
currents that interact with the
magnetic field of the stator to
generate the forces that turn the
shaft.

13. The stationary part is
the stator, usually has
either windings or
permanent magnets.

15. High voltage and rotating
parts can cause serious or fatal
injury. Safe installation,
operation, and maintenance must
be performed by qualified
personnel. Familiariza- tion with
and adherence to NEMA MG2,
the National Electrical Code

16. It is important to observe safety
precautions to protect
personnel from possible injury.
Personnel should be instructed
1.
to: Be familiar with the
equipment and read all
instructions thoroughly before
installing or working on
equipment.

17. 2. Avoid contact with energized
circuits or rotating parts.
3. Disconnect all power sources
before initiating any maintenance
or repair.
4. Act with care in accordance
with prescribed procedures in
handling and lifting this

18. 5. Be sure unit is electrically
grounded in accordance with code
requirements.
6. Be sure equipment is properly
enclosed or protected to prevent
access by children or other
unauthorized personnel in order to
prevent possible accidents.

19. 7. Be sure shaft key is fully
captive before unit is energized.
8. Avoid contact with capacitors
until safe discharge procedures
have been completed.

20. 9. Provide proper guarding for
personnel against rotating parts
and applications involving high
inertia loads which can cause over
speed.
10. Avoid extended exposure to
equipment with high noise levels.

21. Before servicing motors and
motor-operated
equipment, disconnect the power
supply to the motor and accessories.
An electrical lockout/tagout procedure
is recommended, where every piece of
equipment serviced is logged, and
electrical disconnects are physically
disabled.

22. The following best practices will
reduce the cost of operation and
maintenance:

23. Turn Off Unneeded Motors
Identify motors that run
unnecessarily, and turn them off
when appropriate. Examples
include exhaust fans running
when ventilation needs are met,
and escalators operating after
closing. You may need to
reprogram the building control

24. Reduce the Use of the
Motor System
Increasing the efficiency of
mechanical systems can reduce
the amount of time that
associated motors need to run.

25. For example, improving the
performance of a cooling tower
can reduce the run time that the
fans need to reject the same
amount of heat.

26. Eliminating excessive starts
and stops is also worthwhile.
Starting and stopping a motor
stresses its parts and degrades
its performance. Frequent stops
and starts increase the need for
maintenance.

27. Best Practices for
Maintenance
Properly selected and installed
motors can operate for many
years with minimal maintenance.
Nonetheless, regular care will
extend their life and maximize
their energy efficiency.

28. In addition to periodic
upkeep, good recordkeeping
and smart replacement planning
are key elements of a good
motor- maintenance program.

29. Regular Upkeep
Clean motor surfaces and
ventilation openings
periodically. Heavy
accumulations of dust and lint
will result in overheating and
premature motor failure.

30. Properly lubricate moving
parts.
Some motors have sealed
bearings that require no
servicing. For others, regular
lubrication will avoid
unnecessary wear. Be sure to
apply appropriate types and
quantities of lubricant. Applying
too little or too much can harm

31. Keep motor couplings properly
aligned.
Correct shaft alignment
ensures smooth, efficient
transmission of power from the
motor to the load. Incorrect
alignment puts strain on bearings
and shafts, shortening their lives
and reducing system efficiency.

32. Shafts should be parallel and
directly in line with each other.
Shaft alignment should be
checked and adjusted regularly.
Many couplings have hard
rubber inserts that can degrade,
so rubber dust on the equipment
base may indicate problems.

33. Properly align and tension
belts and pulleys when they
are installed, and inspect them
regularly to ensure that
alignment and tension stay
within tolerances.
Abnormal wear patterns on
belts may indicate problems.
Loose belts may squeal and will
slip on the pulley, generating

34. Correctly tensioned pulleys run
cool. Excessive tension strains
bearings and shafts, and
shortens their lives.

35. Maintain bearings by keeping
them clean, lubricated, and
loaded within tolerances.
Proper belt tension or shaft
alignment minimizes strain on
the bearings and helps them
achieve their expected life.

36. These can be prone to shaft
currents, which can cause serious
damage to the bearings.
Fortunately, there are several
technologies that can mitigate
shaft-current problems.

37. Check for proper supply
voltages.
Unbalanced power—that is,
three-phase motors where the
supply voltage to the phases
varies by more than 1%—can
lead to overheating and reduced
motor life. So too can situations
where the supply voltage is
much higher or lower than the

38. Avoid painting motor
housings.
Paint acts as
insulation, increasing operating
temperatures and shortening
motor life. One coat of paint has
little effect, but years of paint
buildup can have a significant
effect.

39. Periodically inspect
commutators visually.
Potential problems with
commutators (which are only
required for DC motors with
brushes) will be seen as
discolorations, flat spots, or
burn marks.

40. Color patterns can be normal as
long as they appear around the
entire commutator. If you notice
problems, remove and repair
the commutator, or replace key
components.

41. Maintain an up-to-date motor
inventory.
The inventory should include
all substantial motors, but can
begin with the largest and those
with the longest run times.

42. This inventory lets facility
managers make informed
choices about replacement,
either before or after a motor
fails. Field-testing motors before
they fail can help ensure that
replacements are properly
sized.

43. Keep maintenance logs.
These logs should contain
vital information such as the
make, model, serial
number, type, and specifications
of each motor; the locations and
specifications for
belts, pulleys, etc.; and a
historical record of maintenance

44. This helps the maintenance
staff remember when tests,
inspections, or servicing are due.
It also allows the staff to quickly
identify spare parts or
replacements when needed. In
addition, comparing recent test
results to past values can provide
early indications of reduced motor

45. Maintenance Schedule for Motors
Description
Comments
Motor use/sequencing
Maintenance Frequency Turn off or sequence unnecessary motors.
Overall
Verify equipment is operating
Weekly visual inspection
Weekly
and safety systems are in place.
Check bearings
Inspect for wear, and adjust, repair
Weekly
and drive belts
or replace as necessary.
Motor alignment
Look for rubber or steel savings under
Weekly
couplings, or listen for odd noises,
as these may indicate a problem).
Motor condition
Check condition by analyzing temperature Quarterly (or as needed
on
or vibration, and compare to baseline values. weekly inspections)
Cleaning
Remove dust and dirt to facilitate cooling.
Quarterly
Check lubrication
Ensure bearings are lubricated
Annually
(or based on run hour
as recommended by manufacturer.
Check mountings
Secure any loose mountings.
Annually
Check terminal tightness
Tighten any loose connections.
Annually balanced
Check for
Troubleshoot unbalanced motor circuit and
Annually
three-phase power
fix problems if the voltage imbalance problems1%.
Check for over- or
Troubleshoot motor circuit and fix exceeds Annually
under- voltage conditions
if the supply voltage differs
significantly from rated voltages.

47. Dirt and Corrosion
•Wipe, brush, vacuum or blow
accumulated dirt from the frame
and air passages of the motor.
Dirty motors run hot when thick
dirt insulates the frame and
clogged passages reduce cooling
air flow. Heat reduces insulation
life and eventually causes motor
failure.

48. •Feel for air being discharged
from the cooling air ports. If the
flow is weak or unsteady,
internal air passages are
probably clogged. Remove the
motor from service and clean.

49. •Check for signs of corrosion.
Serious corrosion may indicate
internal deterioration and/or a
need for external repainting.
Schedule the removal of the
motor from service for complete
inspection and possible
rebuilding.

50. •In wet or corrosive
environments, open the conduit
box and check for deteriorating
insulation or corroded terminals.
Repair as needed.

51. Lubrication
Lubricate the bearings only
when scheduled or if they are
noisy or running hot. Do NOT
over-lubricate. Excessive grease
and oil creates dirt and can
damage bearings.

53. Heat, Noise and Vibration
Feel the motor frame and
bearings for excessive heat or
vibration. Listen for abnormal
noise. All indicate a possible
system failure. Promptly identify
and eliminate the source of the
heat, noise or vibration.

54. Heat
Excessive heat is both a
cause of motor failure and a
sign of other motor problems.
Overheating results from a
variety of different motor
problems.

55. They can be grouped as follows:
•WRONG MOTOR: It may be too
small or have the wrong starting
torque characteristics for the
load. This may be the result of
poor initial selection or changes
in the load requirements.

56. •POOR COOLING: Accumulated
dirt or poor motor location may
prevent the free flow of cooling air
around the motor. In other cases,
the motor may draw heated air
from another source. Internal dirt
or damage can prevent proper air
flow through all sections of the
motor.

57. Dirt on the frame may prevent
transfer of internal heat to the
cooler ambient air.

58. •OVERLOADED DRIVEN
MACHINE: Excess loads or
jams in the driven machine
force the motor to supply
higher torque, draw more
current and overheat.

59. Motor
Horsepower
Light
Duty(1)
Up to 7-1/2
10 to 40
50 to 150
Over 150
10 years
7 years
4 years
1 year
Standard
Duty(2)
Heavy
Duty(3)
7 years
4 years
4 years
1-1/2 years
1-1/2 years 9 months
6 months
3 months
Severe
Duty(4)
9 months
4 months
3 months
2 months

60. •Light Duty: Motors operate
infrequently (1 hour/day or less)
as in portable floor sanders,
valves, door openers.
•Standard Duty: Motors operate
in normal applications (1 or 2
work shifts).

61. Examples include air
conditioning units, conveyors,
refrigeration apparatus, laundry
machinery, woodworking and
textile machines, water pumps,
machine tools, garage
compressors.

62. •Heavy Duty: Motors subjected to
above normal operation and
vibration (running 24 hours/day,
365 days/year). Such operations
as in steel mill service, coal and
mining machinery, motorgenerator sets, fans, pumps.
•Severe Duty: Extremely harsh,
dirty motor applications. Severe
vibration and high ambient
conditions often exist.

63. •EXCESSIVE FRICTION:
Misalignment, poor bearings
and other problems in the driven
machine, power transmission
system or motor increase the
torque required to drive the loads,
raising motor operating
temperature.

64. •ELECTRICAL OVERLOADS:
An electrical failure of a
winding or connection in the
motor can cause other Windings
or the entire motor to overheat.

65. Noise and Vibration
Noise indicates motor
problems but ordinarily does not
cause damage. Noise, however,
is usually accompanied by
vibration.
Vibration can cause damage in
several ways.

66. It tends to shake windings
loose and mechanically
damages insulation by cracking,
flaking or abrading the material.

67. Winding Insulation
When records indicate a
tendency toward periodic winding
failures in the application, check
the condition of the insulation with
an insulation resistance test. Such
testing is especially important for
motors operated in wet or
corrosive atmospheres or in high

68. Cleaning and Drying Windings
Motors which have been
flooded or which have low
megger readings because of
contamination by moisture, oil or
conductive dust should be
thoroughly cleaned and dried.
The methods depend upon
available equipment.

69. A hot water hose and detergents
are commonly used to remove
dirt, oil, dust or salt
concentrations from rotors,
stators and connection boxes.
After cleaning, the windings must
be dried, commonly in a forceddraft oven. Time to obtain
acceptable megger readings
varies from a couple hours to a

71. Basic tools

72. Vibration measurement
tools

74. Electrical discharge
detector

75. Thermal scanner

76. Thermal image