(” NOTE- In this post, ‘motor’ word used for Induction motors only !” )
Induction motors are widely used in industrial, commercial, and residential applications because of their simple construction and reliability. However, improper electrical conditions, mechanical stress, and environmental factors can significantly reduce their lifespan.
This post will further discuss about the reasons that are responsible for its damage. In along with the remedies to prevent these damages.
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Winding is the softest part of motor. Winding is the combination of coils arranged & connected in particular pattern. Most of the cases, Motor get damaged when winding get damaged.
Winding get damaged due to major 7 following reasons :
- Overload
- Wrong & loose connections
- Material ingression
- Single phasing
- Over Voltage & Under Voltage
- Bearing failure & mechanical issue
- Frequent starting & stopping
Next, These reasons are briefly discussed. In along with preventive remedies !
1. OVERLOADING
One major reason of motor damage is ‘OVERLOADING’ !
Overload generally means ‘more than the capacity’. Load output at motor shaft becomes higher than rated value. At this point of overload; torque becomes higher & speed becomes lower. High torque results in high current. High current results in High I ² R loss. At last result, Temperature increases which damages the motor’s winding.
Overload for short interval don’t harm the motor instantly. Damage occurs to the motor when overload occurred many times OR overload get occurred for long period of time.
Reasons of Overloading
- Due to Bearing faults : Rotor of motor rotates freely with the help of bearings on both deriving end & non-deriving ends. When one of the bearing get damaged, it overloads the motor.
- Due to excess load burden : Load at motor’s shaft output; should be lower than the rated value. Excess load creates overload on motor.
Symptoms of overloading
- Overheating
- Excess noise & vibration
- Extra torque
- Extra current consumption
Remedies for overloading
- Thermal overload relay of proper rating should be installed for overload protection.
- Lubrication should be inspected at regular intervals.
- Sound & Temperature also be monitored at regular intervals.
2. LOOSE OR WRONG CONNECTIONS
These are the 2 different reasons of motor damage.
- Damage due to Loose connections
- Damage due to wrong connections
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Connection plate of 3 phase 1.5KW Induction motor
Damage due to loose connections
“Every single connection should be tight. 1 Loose connection can damage the whole system. Loose connection is like a crime in Electrical!”
Similar the case with the motor, Terminal connections should be tightened at rated torque. Loose connection creates sparking which results transients get created in power line. Moreover;
- Loose connection Sparking at terminal plate create carbon between the leads. Current don’t flow properly, some time it conducts or some time not. This creates the situation of 1single phasing. At this stage, motor don’t burn instantly, it takes some time to get damaged.
- Loose connection sparking also creates high temperature around the periphery. This high temperature burns the motor leads after that leads get broken or earthed with motor body.
Damage due to wrong connections
Motor terminals should be connected to rated power supply. Before connecting motor with power supply, Power rating should be cross verified.
3 Phase Motor connections ‘star or delta’ must be according to the rated parameters which are printed on motor’s name plate. Connect the motor in Delta connection only when it is prescribed on name plate. If by chance, A star configured motor get connected in delta, It will burn the motor instantly as explained below :
Three phase motor has 3 set of coils, each set internally is individual not connected with other coil sets.(when all the six leads are out)
Each set has 2 leads therefor 3 sets have total 6 leads.
- When connection in star, Each set gets voltage of phase-Neutral.(single phase)
- When connection in Delta, Each set gets voltage of phase1-phase 2. (Double phase)
If set is capable of handle single phase voltage (Star connection) & motor get connected in Delta, Motor will get burn.
Connections ‘star or delta’ should be made in correct way.
Star & Delta connection diagrams are explained below:
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- STAR DELTA WINDING CONFIGURATION
As explained above, there are total 3 sets.
u+u1, v+v1, w+w1.
Each set is individual not connected with each other internally.
- STAR Connections
For STAR Connections, Short one sided 3 leads with each other. This short junction becomes ‘Neutral‘. The basic requirement for star connection is ‘Single phase (phase-Neutral) supply appears across single set.
- DELTA Connections
For Delta Connections, Connect the leads of one particular set with another set so that a series connection is made.
The basic requirement for Delta connection is ‘2 phases should be connected to each set’ so that double phase appears across the each set.
Causes of loose & wrong connections
- Unskilled workforce
- lack of identification
- Corrosion
- Inferior cable lugs
Symptoms of loose & wrong connections
- Carbonized terminals
- Instant high inrush current at starting
- Extra Vibration
- Humming noise
- No response
Remedies for Wrong OR Loose connections
1.Make a habit of double check. We humans, chances of error are always there from our side. Always try to inspect the connection 2times at least.
2.Before connections always read the name plate first.
3. MATERIAL INGRESSION
Reasons of damage
Motors are solid, tough & powerful Electrical machines. They are made to pull the load But winding inside the motor is; softest part. Winding should be clean at any cost.
Any type of material like iron dust, moisture, water droplets & chemicals can easily damage the winding if they get enter inside the motor.
Material ingression deteriorate the insulation of motor winding which results winding get short circuited or Complete insulation damage.
Common causes
- Harsh operating environments
- Incorrect IP rating selection
- Lack of enclosures or covers
Symptoms
- Reduced cooling
- Rust formation
- Unusual noise from bearings
REMEDIES/PREVENTIONS
- Motor area must be clean & dry. It should be super protected from iron dust, rain & harsh weather conditions.
- Install the motor with Ingress protection according to surrounding environment.
- Connection box cover must be tight perfectly,
4. SINGLE PHASING
Reason of damage
Single phasing is the phenomenon in which motor runs on 2 phases rather than 3. At this stage, Motor consumes excess current & produces humming noise. Motor rotates slower than the rated speed OR In some cases it produces humming noise with no rotation.
Single phasing is most dangerous situation for motor, It burns the motor more rapidly than any other reasons of damage.
Causes of Single phasing
- Single phasing occur when one of the fuse got blown out.
- When contactor’s 1 point get oxidized or damaged.
- When one of the terminal connection is loose or broken, damaged.
Symptoms of single phasing
- Motor humming noise
- Sudden rise in current
- Overheating within minutes
Remedies for single phasing
1.By Using MPCB(Motor Protection Circuit Breaker) or Thermal overload relay; Motor can be protected from 1single phasing.
2. BY using Supply monitoring Device . This device continuously monitors all the 3 phases, it operates when any of the phase get missing. This device makes the system complex & costlier that’s why It is not appropriate using the device on small rating motors.
We can use this device on high rating motors OR we can use this device on main distribution panel where multiple motors are connected.
(If you want to know about supply monitoring device you can go through our post of Supply monitoring Device .)
5. OVER-VOLTAGE & UNDER-VOLTAGE
Why it damages the motor
Electric Motors are designed to work at particular voltage range beyond these range motors don’t work precisely. It works efficiently at rated stable voltage.
Voltage fluctuation can harm the motor if fluctuation is wide. Both Over voltages & Under Voltages are harmful for the motor which damages the motor due to different reasons.
–Over Voltage links with Insulation- Higher the Voltage produces more electric stress on Insulation !
High Voltage produces excess Electric stress between the coils; this stress can deteriorate the insulation of the winding.
–Under Voltage links with high current- Current becomes higher when voltage is lower !
This current can goes beyond the rated value & increase the motor temperature. At this stage, Motor rotates slower & don’t work precisely.
Common causes
- Uneven loading across phases
- Poor power quality
- Faulty distribution system
Symptoms
- Excessive vibration
- Abnormal heating
- Reduced torque output
REMEDY/PREVENTION
1.Voltage stabilizer should be install to eliminate the voltage fluctuation.
2. Over voltage, Under Voltage protection device should be install to monitor the power supply.
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Under Voltage Relay by TEKNIKA
6. Bearing failure & mechanical issue
Why it damages the motor
Bearings support the rotor and ensure smooth operation. Worn or damaged bearings cause misalignment, increased friction, and excessive vibration, which can damage the rotor and stator windings.
Common causes
- Improper lubrication
- Shaft misalignment
- Excessive belt tension
Symptoms
- Grinding or whining noise
- Increased vibration
- Rise in operating temperature
Prevention
- Follow proper lubrication schedule
- Align motor and driven equipment accurately
- Avoid over-tightening belts
7. Frequent starting & stopping
Why it damages the motor
Each motor start draws high inrush current, generating heat. Frequent starts without adequate cooling time accelerate insulation aging.
Common causes
- Poor process design
- Manual switching instead of automation
Symptoms
- Frequent tripping
- Overheated windings
Prevention
- Use soft starters or VFDs
- Limit the number of starts per hour as per motor specification
How to Increase the Life of an Induction Motor
- Use proper electrical protection (overload, short circuit, phase failure)
- Maintain good ventilation and cleanliness
- Perform periodic inspections and testing
- Operate the motor within rated limits
Frequently Asked Questions (FAQs)
What is the most common cause of induction motor failure?
Overheating due to overloading and poor power quality is the most common cause.
Can voltage fluctuation damage an induction motor?
Yes. Continuous voltage imbalance or fluctuation increases current and reduces motor lifespan.
How can I protect a motor from single phasing?
By installing a phase failure relay or single phasing preventer.
Does dust really affect motor performance?
Yes. Dust blocks cooling paths and increases internal temperature, leading to insulation failure.
CONCLUSION
- 3 Phase Induction motors are more preferred motors in industry.
- Winding is the softest part of the motor. Most of the cases, Motor get damaged when winding get harmed.
- Winding get damages due to 7 major reasons & that are : Overload, wrong or loose connection, Material Ingression, Single phasing, Over voltage & under voltage, Mechanical damage, frequent starting & stopping.
- All the 7 major reasons are preventable through some of the steps. These steps should be consider at any circumstances.
- Induction motors damage is usually preventable with proper selection, protection, and maintenance. Understanding the common failure causes and acting early can save downtime, repair costs, and extend motor life significantly.
- If you work with motors regularly, make preventive maintenance a priority — it always costs less than motor replacement.
This is all about the reasons that damages the motor. Hope! You like the post. If you have any doubt, suggestion or query please do comments.
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