p–ISSN: 2723 - 6609 e-ISSN: 2745-5254
Vol. 5, No. 11, November 2024 http://jist.publikasiindonesia.id/
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4769
Common Faults and Maintenance of Three-phase AC
Asynchronous Motors
Guan yu1*, Indra Yuliarta2*
DSSP Power Kendari Company, Indonesia
Email: [email protected]1*, [email protected]2*
*Correspondence
ABSTRACT
Keywords: common fault,
processing method, three-
phase AC async motor.
Application of three-phase AC asynchronous motor in
industrial applied in many aspect following function that
need to use. In operation use, many troubles may cause
motor equipment not to operate or break down by the motor
itself or caused by a system including protection, control
system, interlocking device, and others causes. Aiming at the
actual situation that three-phase AC asynchronous motors
are widely used and have a high failure rate, this paper
focuses on analyzing the common failures and abnormal
phenomena of three-phase AC asynchronous motors and
their main causes. This Research Method is reinforced by the
actual monitoring of the locality where the equipment is
installed. At the same time, some specific preventive
measures and treatment methods are proposed to timely
discover and eliminate the potential accidents of motors as
much as possible and ensure the safe operation of motors. In
conclusion, the aspects that need to be considered are one by
one. There are 2 general classifications to determine possible
faults, the first is about the operating conditions that the
equipment motor should monitor and take the scheduled data
to know about the actual conditions including power quality,
temperature rise, vibration analysis, and physical
abnormalities during the operation of the unit.
Introduction
The three-phase AC asynchronous motor is the most common electrical equipment
in industrial and agricultural production. Its function is to convert electrical energy into
mechanical energy (Braunovic et al., 2017). It plays a huge role in industrial and
agricultural production and brings great convenience to people's lives. It is also the most
used motor. It has a simple structure, easy start-up, small size, reliable operation, strong
and durable, and easy maintenance and repair (EKO, 2020). To ensure the safe operation
of asynchronous motors, electrical workers must master the basic knowledge about the
safe operation of asynchronous motors, understand the safety assessment of asynchronous
motors, and do their best to discover and eliminate the hidden dangers of motor accidents
Vol. 5, No. 11, November 2024 http://jist.publikasiindonesia.id/
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4769
Common Faults and Maintenance of Three-phase AC
Asynchronous Motors
Guan yu1*, Indra Yuliarta2*
DSSP Power Kendari Company, Indonesia
Email: [email protected]1*, [email protected]2*
*Correspondence
ABSTRACT
Keywords: common fault,
processing method, three-
phase AC async motor.
Application of three-phase AC asynchronous motor in
industrial applied in many aspect following function that
need to use. In operation use, many troubles may cause
motor equipment not to operate or break down by the motor
itself or caused by a system including protection, control
system, interlocking device, and others causes. Aiming at the
actual situation that three-phase AC asynchronous motors
are widely used and have a high failure rate, this paper
focuses on analyzing the common failures and abnormal
phenomena of three-phase AC asynchronous motors and
their main causes. This Research Method is reinforced by the
actual monitoring of the locality where the equipment is
installed. At the same time, some specific preventive
measures and treatment methods are proposed to timely
discover and eliminate the potential accidents of motors as
much as possible and ensure the safe operation of motors. In
conclusion, the aspects that need to be considered are one by
one. There are 2 general classifications to determine possible
faults, the first is about the operating conditions that the
equipment motor should monitor and take the scheduled data
to know about the actual conditions including power quality,
temperature rise, vibration analysis, and physical
abnormalities during the operation of the unit.
Introduction
The three-phase AC asynchronous motor is the most common electrical equipment
in industrial and agricultural production. Its function is to convert electrical energy into
mechanical energy (Braunovic et al., 2017). It plays a huge role in industrial and
agricultural production and brings great convenience to people's lives. It is also the most
used motor. It has a simple structure, easy start-up, small size, reliable operation, strong
and durable, and easy maintenance and repair (EKO, 2020). To ensure the safe operation
of asynchronous motors, electrical workers must master the basic knowledge about the
safe operation of asynchronous motors, understand the safety assessment of asynchronous
motors, and do their best to discover and eliminate the hidden dangers of motor accidents
Guan yu, Indra Yuliarta
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4770
promptly to ensure the safe operation of motors (Bhattacharyya et al., 2011). Electric
motors are exposed to many kinds of disturbances and stress. Part of the disturbances is
due to imposed external conditions such as over- and Under-voltage, over- and under-
frequency, harmonics, unbalanced system voltages, and supply interruptions, for
example, autoreclosing that occurs in the supplying network (Risdiyanto et al., 2013).
Other possible causes of external disturbances are dirt in the motor, cooling system
bearing failures, or an increase in ambient temperature and humidity. Stress factors due
to abnormal use of the motor drive itself are frequent successive startups, stall, and
overload situations including mechanical stress. The above stress and disturbances
deteriorate the winding insulation of the motor mechanically and by increased thermal
aging rate, which may eventually lead to an insulation failure. (ABB Distribution Motor
Handbook Section 8.11 Motor Protection et al.,2011)
1. Select the type of motor according to the surrounding environment where the motor is
installed.
There are two common types of motors: protective and enclosed. The protective
type has better ventilation performance and is low in price. It is suitable for dry
environments with less dust. If there is a lot of dust and water droplets splashing, a closed
motor should be used. In addition, there is a sealed motor that can work in water. Electric
submersible pumps use this type of motor (Popa et al., 2006).
2. Select the power of the motor according to the load conditions.
The power of the motor should generally be 1.1 to 1.5 times the power of the
production machinery. If the power is too large, it will not only increase investment but
also reduce mechanical efficiency and increase production costs. If the power is too small,
the motor will be subjected to excessive load for a long time, which will cause the
temperature to rise too high and damage the insulation, shortening the service life of the
motor. (Tri Ananda, 2024).
The grounding of the motor is an important link, but some units often ignore this
point, because the motor can run without obvious grounding, but this buries unsafe hidden
dangers to production and personal safety. Once the insulation is damaged, the shell will
generate dangerous voltage to the ground, which directly threatens personal safety and
the stability of the equipment. (Khayam et al., 2017). Therefore, the motor must be safely
grounded. The so-called motor grounding is to connect a metal part of the electrical
equipment that is not charged under normal circumstances to the earth through a
grounding device, and the grounding of the motor is the grounding of the metal shell. In
this way, even if the equipment is grounded and the shell is short-circuited, the current
will diffuse hemispherically to the earth through the grounding, and the current will form
a voltage drop when it flows to the earth, thus ensuring the safety of the equipment and
personnel (Lai et al., 2022).
To prevent the motor from burning out during operation, in addition to taking
necessary technical protection measures before the operation, the most effective and
practical way to prevent it is to perform correct technical maintenance. There are mainly
6 points:
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4770
promptly to ensure the safe operation of motors (Bhattacharyya et al., 2011). Electric
motors are exposed to many kinds of disturbances and stress. Part of the disturbances is
due to imposed external conditions such as over- and Under-voltage, over- and under-
frequency, harmonics, unbalanced system voltages, and supply interruptions, for
example, autoreclosing that occurs in the supplying network (Risdiyanto et al., 2013).
Other possible causes of external disturbances are dirt in the motor, cooling system
bearing failures, or an increase in ambient temperature and humidity. Stress factors due
to abnormal use of the motor drive itself are frequent successive startups, stall, and
overload situations including mechanical stress. The above stress and disturbances
deteriorate the winding insulation of the motor mechanically and by increased thermal
aging rate, which may eventually lead to an insulation failure. (ABB Distribution Motor
Handbook Section 8.11 Motor Protection et al.,2011)
1. Select the type of motor according to the surrounding environment where the motor is
installed.
There are two common types of motors: protective and enclosed. The protective
type has better ventilation performance and is low in price. It is suitable for dry
environments with less dust. If there is a lot of dust and water droplets splashing, a closed
motor should be used. In addition, there is a sealed motor that can work in water. Electric
submersible pumps use this type of motor (Popa et al., 2006).
2. Select the power of the motor according to the load conditions.
The power of the motor should generally be 1.1 to 1.5 times the power of the
production machinery. If the power is too large, it will not only increase investment but
also reduce mechanical efficiency and increase production costs. If the power is too small,
the motor will be subjected to excessive load for a long time, which will cause the
temperature to rise too high and damage the insulation, shortening the service life of the
motor. (Tri Ananda, 2024).
The grounding of the motor is an important link, but some units often ignore this
point, because the motor can run without obvious grounding, but this buries unsafe hidden
dangers to production and personal safety. Once the insulation is damaged, the shell will
generate dangerous voltage to the ground, which directly threatens personal safety and
the stability of the equipment. (Khayam et al., 2017). Therefore, the motor must be safely
grounded. The so-called motor grounding is to connect a metal part of the electrical
equipment that is not charged under normal circumstances to the earth through a
grounding device, and the grounding of the motor is the grounding of the metal shell. In
this way, even if the equipment is grounded and the shell is short-circuited, the current
will diffuse hemispherically to the earth through the grounding, and the current will form
a voltage drop when it flows to the earth, thus ensuring the safety of the equipment and
personnel (Lai et al., 2022).
To prevent the motor from burning out during operation, in addition to taking
necessary technical protection measures before the operation, the most effective and
practical way to prevent it is to perform correct technical maintenance. There are mainly
6 points:
Common Faults and Maintenance of Three-phase AC Asynchronous Motors
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4771
1. Always keep the motor clean. When the motor is running, dust, water stains, and other
debris are not allowed within at least 3 meters of the air inlet to prevent them from
being sucked into the motor, forming a short-circuit medium, or damaging the
insulation layer of the wire, causing a short circuit between turns, increasing current,
and increasing temperature, which can burn the motor. Therefore, it is necessary to
ensure that the motor has sufficient insulation resistance and a good ventilation and
cooling environment to keep the motor in a safe and stable working state during long-
term operation.
2. Keep the motor working at the rated current. The main reasons for motor overload are
excessive load, low voltage, or mechanical jamming. If the overload time is too long,
the motor will absorb a large amount of active power from the power grid, the current
will increase sharply, and the temperature will rise accordingly. Under high
temperatures, the insulation of the motor will age and burn out. Therefore, when the
motor is running, it is necessary to pay attention to check whether the transmission
device is flexible and reliable, whether the concentricity of the coupling is standard,
and the flexibility of the gear transmission. If jamming is found, the motor should be
stopped immediately to find out the cause and eliminate the fault before running again.
Ensure the normal operation of the starting equipment The technical status of the
motor starting equipment plays a decisive role in the normal starting of the motor. The
practice has shown that the vast majority of burnt motors are caused by the abnormal
operation of the starting equipment. For example, the starting equipment starts with a
phase loss, the contactor contacts arc, spark, etc. The maintenance of the starting
equipment is mainly cleaning and tightening (RASYID, 2020). If the contactor contacts
are not clean, the contact resistance will increase, causing heat to burn the contacts,
resulting in phase loss and burning the motor; the iron core of the contactor suction coil
is rusted and dusty, which will cause the coil to be loosely attracted, and strong noise will
occur, increasing the coil current, burning the coil and causing failures. Therefore, the
electrical control cabinet should be located in a dry, ventilated, and easy-to-operate
location, and dust should be removed regularly. Frequently check whether the contactor
contacts, coil cores, and various wiring screws are reliable and whether the mechanical
parts are flexible so that they are kept in a good technical state, thereby ensuring smooth
starting without burning the motor (Sheng & Wang, 2015).
This research tries to analyze and prove that the results of many conditions and also
treatment for Three-phase induction motor can perform and indicate the preliminary
actual condition of each motor.
Research Method
Actual Monitoring and Visual Examination
This research strengthens with actual monitoring of local where equipment
is installed, the purpose of this method is to know the actual condition of equipment
including:
a. Cleanliness of body motor and cooling way
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4771
1. Always keep the motor clean. When the motor is running, dust, water stains, and other
debris are not allowed within at least 3 meters of the air inlet to prevent them from
being sucked into the motor, forming a short-circuit medium, or damaging the
insulation layer of the wire, causing a short circuit between turns, increasing current,
and increasing temperature, which can burn the motor. Therefore, it is necessary to
ensure that the motor has sufficient insulation resistance and a good ventilation and
cooling environment to keep the motor in a safe and stable working state during long-
term operation.
2. Keep the motor working at the rated current. The main reasons for motor overload are
excessive load, low voltage, or mechanical jamming. If the overload time is too long,
the motor will absorb a large amount of active power from the power grid, the current
will increase sharply, and the temperature will rise accordingly. Under high
temperatures, the insulation of the motor will age and burn out. Therefore, when the
motor is running, it is necessary to pay attention to check whether the transmission
device is flexible and reliable, whether the concentricity of the coupling is standard,
and the flexibility of the gear transmission. If jamming is found, the motor should be
stopped immediately to find out the cause and eliminate the fault before running again.
Ensure the normal operation of the starting equipment The technical status of the
motor starting equipment plays a decisive role in the normal starting of the motor. The
practice has shown that the vast majority of burnt motors are caused by the abnormal
operation of the starting equipment. For example, the starting equipment starts with a
phase loss, the contactor contacts arc, spark, etc. The maintenance of the starting
equipment is mainly cleaning and tightening (RASYID, 2020). If the contactor contacts
are not clean, the contact resistance will increase, causing heat to burn the contacts,
resulting in phase loss and burning the motor; the iron core of the contactor suction coil
is rusted and dusty, which will cause the coil to be loosely attracted, and strong noise will
occur, increasing the coil current, burning the coil and causing failures. Therefore, the
electrical control cabinet should be located in a dry, ventilated, and easy-to-operate
location, and dust should be removed regularly. Frequently check whether the contactor
contacts, coil cores, and various wiring screws are reliable and whether the mechanical
parts are flexible so that they are kept in a good technical state, thereby ensuring smooth
starting without burning the motor (Sheng & Wang, 2015).
This research tries to analyze and prove that the results of many conditions and also
treatment for Three-phase induction motor can perform and indicate the preliminary
actual condition of each motor.
Research Method
Actual Monitoring and Visual Examination
This research strengthens with actual monitoring of local where equipment
is installed, the purpose of this method is to know the actual condition of equipment
including:
a. Cleanliness of body motor and cooling way
Guan yu, Indra Yuliarta
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4772
b. Terminal box condition regarding corrosion or mechanical damage
c. Grounding connection
d. Appearance of noise at bearing and cooling fan
e. Cable condition including connection and conduit protection
Equipment Monitoring with Measurement Tools
Thermal Imaging Camera
Actual measurement of temperature when equipment is running is very necessary
related to the temperature rises. Abnormal temperature can be defined by a Thermal
imaging camera scanning at body motor and also the terminal connection.
Vibration Analyser
Measurement of vibration rotating equipment holds a main role in knowing the
actual vibration that is generated when the unit running. Taking data using a Vibration
analyzer can define the value of the vibration and also can make a preliminary diagnosis
from the measurements.
Power Analyser
During equipment running, monitoring electrical parameters is helpful also to know
about the health level of rotating equipment. The value of current for each phase
(ampere), active power, and also reactive power can be monitored by Power Analyser
tools.
Assessment Test 3 Phase Asynchronous Motor and MCC Equipment
Assessment Test of rotating equipment during stop condition is necessary to know
the condition of the motor after running during unit power plant operation. Not only the
rotating equipment that needs to be assessed, but supporting equipment also needs to be
assessed to make sure no abnormal condition can affect the motor to operate or break
down.
Insulation Resistance (IR) and Polarisation Index (PI) Test
The insulation Resistance Test (IR) aims to know about of insulation winding
condition that works to protect the winding short with the body or grounding point.
The Polarisation Index or PI Test defines fouling conditions that may arise because
of environment or residue during operate a winding motor. An insulation Resistance test
was also done at the cable power of the motor to avoid any ground leaking condition.
Winding Resistance (WR) Test
Winding Resistance (WR) Test used to measure the value of each phase (separate)
winding motor and/or in Y or Delta connection. This assessment test is very useful to
define the stability of resistance value.
Contact Resistance Test of MCC (Contactor and Primary Contact)
Contact resistance test of MCC Equipment to measure the value of resistance for
each power contact that transferred big ampere to the motor still in below maximum
standard value.
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4772
b. Terminal box condition regarding corrosion or mechanical damage
c. Grounding connection
d. Appearance of noise at bearing and cooling fan
e. Cable condition including connection and conduit protection
Equipment Monitoring with Measurement Tools
Thermal Imaging Camera
Actual measurement of temperature when equipment is running is very necessary
related to the temperature rises. Abnormal temperature can be defined by a Thermal
imaging camera scanning at body motor and also the terminal connection.
Vibration Analyser
Measurement of vibration rotating equipment holds a main role in knowing the
actual vibration that is generated when the unit running. Taking data using a Vibration
analyzer can define the value of the vibration and also can make a preliminary diagnosis
from the measurements.
Power Analyser
During equipment running, monitoring electrical parameters is helpful also to know
about the health level of rotating equipment. The value of current for each phase
(ampere), active power, and also reactive power can be monitored by Power Analyser
tools.
Assessment Test 3 Phase Asynchronous Motor and MCC Equipment
Assessment Test of rotating equipment during stop condition is necessary to know
the condition of the motor after running during unit power plant operation. Not only the
rotating equipment that needs to be assessed, but supporting equipment also needs to be
assessed to make sure no abnormal condition can affect the motor to operate or break
down.
Insulation Resistance (IR) and Polarisation Index (PI) Test
The insulation Resistance Test (IR) aims to know about of insulation winding
condition that works to protect the winding short with the body or grounding point.
The Polarisation Index or PI Test defines fouling conditions that may arise because
of environment or residue during operate a winding motor. An insulation Resistance test
was also done at the cable power of the motor to avoid any ground leaking condition.
Winding Resistance (WR) Test
Winding Resistance (WR) Test used to measure the value of each phase (separate)
winding motor and/or in Y or Delta connection. This assessment test is very useful to
define the stability of resistance value.
Contact Resistance Test of MCC (Contactor and Primary Contact)
Contact resistance test of MCC Equipment to measure the value of resistance for
each power contact that transferred big ampere to the motor still in below maximum
standard value.
Common Faults and Maintenance of Three-phase AC Asynchronous Motors
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4773
Results and Discussion
Actual Monitoring and Visual Examination
An environment that places rotating equipment is not limited only to indoor areas
with clean conditions, there are many motors installed in dirty and open areas that may
affect the equipment's performance. The deposit of dust usually collected at the fin of
the airway body motor that causes heat produced during operation cannot be released.
Equipment Monitoring with Measurement Tools
Thermal Imaging Camera
Monitoring of actual temperature motor during running conditions is necessary to
map the highest temperature at the surface area of the motor. Areas that show the highest
temperature need to be analyzed and made sure still in standard or already over.
Increasing the temperature of the motor can increase the friction of the bearing with
the housing bearing and also cause by winding temperature that is loaded.
Regarding the Insulation Class of Motor, in general use minimum standard of
Insulation Class is an F Grade. It means that the temperature working of the motor is not
more than 155°C in the highest value. Of attached picture shows that during actual
monitoring activity, measurements are at the surface area of the body motor with record
the highest value.
Table 1
of NEMA Standard for Motor Insulation Class
NEMA Motor
Insl. Temperature
Ratings
Temperature Rise
1.0 SF Motors 1.15 SF Motors
Class Temp. Ambient Hotspots Rise @1.0 Rise @1.15
A 105 +40 +5 60 70
B 130 +40 +10 80 90
F 155 +40 +10 105 115
H 180 +40 +20 125 Not Defined
Figure 1
Actual Measurement of Body Motor
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4773
Results and Discussion
Actual Monitoring and Visual Examination
An environment that places rotating equipment is not limited only to indoor areas
with clean conditions, there are many motors installed in dirty and open areas that may
affect the equipment's performance. The deposit of dust usually collected at the fin of
the airway body motor that causes heat produced during operation cannot be released.
Equipment Monitoring with Measurement Tools
Thermal Imaging Camera
Monitoring of actual temperature motor during running conditions is necessary to
map the highest temperature at the surface area of the motor. Areas that show the highest
temperature need to be analyzed and made sure still in standard or already over.
Increasing the temperature of the motor can increase the friction of the bearing with
the housing bearing and also cause by winding temperature that is loaded.
Regarding the Insulation Class of Motor, in general use minimum standard of
Insulation Class is an F Grade. It means that the temperature working of the motor is not
more than 155°C in the highest value. Of attached picture shows that during actual
monitoring activity, measurements are at the surface area of the body motor with record
the highest value.
Table 1
of NEMA Standard for Motor Insulation Class
NEMA Motor
Insl. Temperature
Ratings
Temperature Rise
1.0 SF Motors 1.15 SF Motors
Class Temp. Ambient Hotspots Rise @1.0 Rise @1.15
A 105 +40 +5 60 70
B 130 +40 +10 80 90
F 155 +40 +10 105 115
H 180 +40 +20 125 Not Defined
Figure 1
Actual Measurement of Body Motor
Guan yu, Indra Yuliarta
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4774
Not only actual temperature measurement of the motor, but other equipment that
support unit of the motor can operate normally also must do actual monitoring. It's to
ensure that the motor operates in a safe condition. The Motor Control Centre also called
MCC plays a critical role in supplying power to the motor, The current that is transferred
goes through the motor flowing from the MCC part, and the power cable produces excess
heat that must be monitored during unit operation. Many factors can affect excess heat
increase during unit operation that may initial dangerous conditions if not measure the
actual condition.
Figure 2
Actual Monitoring Measure Temperature MCC
Figure 3
Excess heat causing damage to part of MCC Equipment
Vibration Analyser
Measure the vibration value of rotating equipment including 3 3-phase motors is
necessary to know the actual condition of the motor following bearing condition, rotation,
lack of lubrication, and other abnormalities. The vibration of the motor can be measured
using a vibration motor and also a vibration analyzer to deeply analyze the actual
condition that happens at the motor. The results of vibration measurement can refer to
the ISO 10816 standard.
Indonesian Journal of Social Technology, Vol. 5, No. 11, November 2024 4774
Not only actual temperature measurement of the motor, but other equipment that
support unit of the motor can operate normally also must do actual monitoring. It's to
ensure that the motor operates in a safe condition. The Motor Control Centre also called
MCC plays a critical role in supplying power to the motor, The current that is transferred
goes through the motor flowing from the MCC part, and the power cable produces excess
heat that must be monitored during unit operation. Many factors can affect excess heat
increase during unit operation that may initial dangerous conditions if not measure the
actual condition.
Figure 2
Actual Monitoring Measure Temperature MCC
Figure 3
Excess heat causing damage to part of MCC Equipment
Vibration Analyser
Measure the vibration value of rotating equipment including 3 3-phase motors is
necessary to know the actual condition of the motor following bearing condition, rotation,
lack of lubrication, and other abnormalities. The vibration of the motor can be measured
using a vibration motor and also a vibration analyzer to deeply analyze the actual
condition that happens at the motor. The results of vibration measurement can refer to
the ISO 10816 standard.