1. Introduction
Induction motors (IMs) are integral to modern industrial operations due to their robustness, simplicity, cost-effectiveness, and low maintenance. Their consistent performance over a wide range of functions, from mining, electric vehicles, Heating, Ventilation and Air-conditioning (HVAC) systems to manufacturing makes them a preferred choice for both light and heavy-duty applications. Their widespread adoption is largely attributed to mechanical reliability and efficiency
. Despite these advantages, induction motors are vulnerable to mechanical vibrations which can cause thermal and significant operational issues. These vibrations may result from rotor imbalance, bearing defects, loosened mechanical parts, rotor or stator core damage, misalignment, and external environmental influences like structural resonance and foundation instability
[2] | Garcia-Calva, T., Duque-Perez, Ó., Romero-Troncoso, R. J., Morinigo-Sotelo, D., Martin-Diaz, I. Detecting Particle Contamination in Bearings of Inverter-Fed Induction Motors: A Comparative Evaluation of Monitoring Signals. Machines. 2025, 13(4), 1-21. https://doi.org/10.3390/machines13040269 |
[2]
. Whilst such faults may initially seem minor, they often accumulate over time, leading to overheating, performance degradation, and in severe cases, system failure. One major consequence of persistent vibration is vibration-induced thermal failure, wherein continuous mechanical excitation produces excessive heat within motor components
[3] | Meyyappan, K., Vujosevic, M., Wu, Q., Malatkar, P., Hill, C., Parrott, R. Vibration-induced Failures In Automotive Electronics: Knowledge-based Qualification Perspective. Journal of Electronic Packaging. 2018, 140(2), 1-12. https://doi.org/10.1115/1.4039301 |
[3]
. Contributing factors include elevated mechanical stress, unbalanced magnetic pull, and increased friction. These disturbances disrupt thermal equilibrium, degrade insulation, accelerates material fatigue, impair efficiency of energy conversion, reduce motor reliability, and increase power consumption. As industries strive to minimise maintenance cost and maximise productivity, early and accurate detection of these thermal anomalies is important. Traditional fault detection methods such as thermal imaging, the use of vibration meters, routine physical inspection although useful, have shortfalls. They often require system downtime, are time-consuming, and prone to human errors. Advanced methods using contact-based instruments or wired sensors complicate system integration and increase operational costs. Moreover, many existing approaches fail to detect early-stage or weak vibration patterns that precede failure
[4] | Ullah, I., Khan, N., Memon, S. A., Kim, W. G., Saleem, J., Manzoor, S. Vibration-Based Anomaly Detection for Induction Motors Using Machine Learning. Sensors (Basel, Switzerland). 2025, 25(3), 1-21. https://doi.org/10.3390/s25030773 |
[4]
. This study seeks to address a critical gap, that is the absence of non-invasive, intelligent, and data-driven system for reliably diagnosing vibration-induced thermal faults in induction motors
[5] | Chikwendu, O. C., Emeka, U. C., Obiuto, N. C. Digital Twin Applications for Predicting And Controlling Vibrations In Manufacturing Systems. World Journal of Advanced Research and Reviews. 2024, 25(1), 1-9. https://doi.org/10.30574/wjarr.2025.25.1.3821 |
[5]
. Artificial intelligence (AI), especially Autoencoders (AEs)-based models, offer a promising solution
[6] | Behrouzi, S., Dix, M., Karampanah, F., Ates, O., Sasidharan, N., Chandna, S., Vu, B. Improving Visual Defect Detection and Localization in Industrial Thermal Images Using Autoencoders. Journal of Imaging. 2023, 9(7), 1-14. https://doi.org/10.3390/jimaging9070137 |
[6]
. These models can analyse large volumes of sensor data to learn normal vibration patterns and detect subtle deviations indicative of emerging faults. Through predictive modelling, AI can be leveraged not only to identify existing issues but also to anticipate future faults before they evolve into catastrophic failures. The primary objectives of this study are to identify and characterise the causes and impacts of vibration-induced thermal faults and to design and implement an AE-based anomaly detection framework. The model is trained and validated using real-world industrial vibration datasets collected under various operating conditions. The key innovation of this study lies in its development of a non-intrusive, AI-based anomaly detection system that leverages unsupervised learning to identify early-stage thermal faults without requiring labelled fault data. Unlike conventional methods, the proposed Autoencoder model detects subtle abnormal vibration patterns by learning from healthy motor data, enabling early intervention. This approach ensures minimal system disruption and offers scalability for real-time monitoring, aligning with the goal of Industry 4.0, where data-driven technologies are reshaping how industrial equipment is optimised and managed
[7] | Hughes, L., Dwivedi, Y. K., Rana, N. P., Williams, M. D., Raghavan, V. Perspectives On The Future of Manufacturing Within The Industry 4.0 Era. Production Planning and Control. 2022, 33(2-3), 138-158. |
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1.1. Causes of Vibration in Induction Motor
1.1.1. Mechanical Imbalance
Induction motor vibration is primarily caused by mechanical imbalance
[8] | Al-Haddad, L. A., Jaber, A. A., Hamzah, M. N., Fayad, M. A. Vibration-current Data Fusion and Gradient Boosting Classifier for Enhanced Stator Fault Diagnosis In Three-phase Permanent Magnet Synchronous Motors. Electrical Engineering. 2024, 106(3), 3253-3268. https://doi.org/10.1007/s00202-023-02148-z |
[8]
. This imbalance occurs when the center of gravity of the rotor or other rotating components deviates from the axis of rotation, resulting in uneven weight distribution. This, in turn, generates centrifugal force during motor operation and that will lead to vibration. There are several types of mechanical imbalances in induction motors. The first is dynamic imbalance and that refers to an uneven weight distribution perpendicular to the axis of rotation
. Then there is static imbalance. This involves uneven weight distribution along the axis
[10] | Kumar, R. R., Andriollo, M., Cirrincione, G., Cirrincione, M., Tortella, A. A Comprehensive Review of Conventional and Intelligence-based Approaches for the Fault Diagnosis and Condition Monitoring of Induction Motors. Energies. 2022, 15(23), 1-36. https://doi.org/10.3390/en15238938 |
[10]
. Also, there is couple imbalance which combines imbalances in both static and dynamic planes to complicate the vibration patterns. Various factors contribute to mechanical imbalance. Manufacturing defects, such as errors in machining or assembly, can result in inherent imbalances. Over time, normal wear and tear may cause component degradation to exacerbate the imbalance. External impacts or collisions can deform motor parts, while improper reassembly or balancing after repairs can introduce further imbalances. Environmental factors, like erosion or corrosion, can disrupt weight distribution and cause material loss. The effects of mechanical imbalance can be significant
[11] | Cogburn, A., Bhattarai, P. Impacts on the Grid-Side Voltage Due to the Current Unbalance Amplification Caused by Induction Motors, In IEEE Texas Power and Energy Conference. IEEE, College Station, TX USA, 2024; pp. 1-6. https://doi.org/10.1109/TPEC60005.2024.10472266 |
[11]
. Increased vibration leads to higher noise levels, which result directly from the vibrational forces. Moreover, imbalance forces cause the motor to consume more energy to maintain performance, whilst reducing efficiency. Long-term imbalance may cause premature wear of bearings and other components, potentially leading to catastrophic motor failure.
1.1.2. Misalignment
Misalignment is a major contributor to vibration in induction motors
[12] | Ruiz-Sarrio, J. E., Biot-Monterde, V., Madariaga-Cifuentes, C., Navarro-Navarro, A., Antonino-Daviu, J. A. On the Utilization of Radial Vibration Transient Signals for Induction Machine Misalignment Diagnosis, In IEEE International Conference on Electrical Machines. IEEE, Torino Italy, 2024; pp. 1-6. https://doi.org/10.1109/ICEM60801.2024.10700185 |
[12]
. It occurs when the motor shaft or bearings are not properly aligned with the driven equipment or its foundation. This misalignment leads to uneven loading and tension on motor components, causing vibrations during operation. These vibrations can result in premature wear, reduced efficiency, and, in severe cases, cause catastrophic motor failure. There are three types of misalignments. These are angular, parallel, and mixed misalignments. Angular misalignment arises when the motor shafts are at an angle to each other rather than running parallel
[13] | Verucchi, C. J., Giraldo, E., Meira, M., Ruschetti, C. R., Bossio, J. M., Bossio, G. R. Efficiency Assessment of Induction Motors Drives Operating Under Shaft Misalignment Conditions. Advances in Electrical and Electronic Engineering. 2020, 18(3), pp. 142-152. https://doi.org/10.15598/aeee.v18i3.3596 |
[13]
. On the other hand, parallel misalignment occurs when the shaft centers are offset despite being parallel
[14] | Rahmawan, H. A., Widjianto, B. L., Indriawati, K. and Ariefianto, R. M. Advancing Fault Diagnosis for Parallel Misalignment Detection in Induction Motors Based on Convolutional Neural Networks. Electrics, Electronics, Communications, Controls, Informatics, and Systems. 2023, 17(2), pp. 66-71. https://doi.org/10.21776/jeeccis.v17i2.1655 |
[14]
. Combined misalignment involves both angular and parallel misalignment, resulting in more complex issues
[15] | Demetgul, M., Zihan, M., Heider, I., Fleischer, J. Misalignment Detection On Linear Feed Axis Using Sensorless Motor Current Signals. International Journal of Advanced Manufacturing Technology. 2023, 126(5), pp. 2677-2691. https://doi.org/10.1007/s00170-023-11258-8 |
[15]
. Several factors can cause misalignment. Improper installation is a common cause, often due to setup errors. Over time, it may also result from foundation settling, equipment shifts, or natural wear of components. Thermal expansion can further contribute, as uneven heating causes parts to expand at varying rates. In addition, maintenance errors such as improper reassembly or misalignment after repairs can intensify the problem. The consequences of misalignment are many and can significantly affect motor performance. It induces vibrations that compromise motor stability and are often accompanied by increased noise and energy consumption. This reduces operational efficiency and accelerates wear on important components such as seals and bearings. If unaddressed, misalignment can eventually lead to motor failure, particularly in high-demand or precision-driven applications.
1.1.3. Bearing Faults
Bearings are essential parts of induction motors, playing a vital function in reducing friction, support rotating shafts, and facilitating smooth operation. They also serve as important interfaces between stationary and rotating parts, while accommodating both radial and axial loads with marginal resistance. Common bearing faults include defects in the inner and outer races, rolling element (balls), and the cage (retainer). These faults can significantly compromise motor stability, leading to increased vibration, uneven load distribution, elevated friction, and eventually premature wear and reduced motor lifespan.
Figure 1 presents a sectional view of a rolling-element bearing. The outer race forms the outermost ring, providing a smooth track for the rolling elements. The balls, typically made from steel or ceramic, rotate between the inner and outer races to reduce friction and enable smooth rotation. The retainer or cage holds the balls in place, ensuring uniformly spacing and preventing direct contact, thereby reducing wear and promoting operational stability. Bearings may develop problems over time due various factors such as lubrication failure, poor maintenance, excessive mechanical loads, contamination, or misalignment. These conditions disrupt uniform load distribution, creating localised stress concentrations that can lead to surface damage. Over time, this manifests as pitting, spalling, or cracking, all of which compromise the bearing’s structural integrity. Such degradation is a primary contributor to vibration anomalies and thermal buildup in the motor. Vibrations originating from damaged bearings can propagate to surrounding components, further increasing mechanical stress and noise levels. Initial signs of bearing failure usually include elevated operating temperatures, irregular noises, and increased energy consumption. If not properly addressed, these issues can escalate into severe mechanical failure. The most common bearing defects involve the outer race, rolling elements, and inner race, as shown in
Figure 2. These failure modes are important indicators in condition monitoring and serves as targets in predictive maintenance strategies.
An outer race fault in a rolling bearing occurs when the outer ring becomes worn or damaged, typically due to contamination, excessive load, or lubrication failure
[18] | Bentrah, W., Bessous, N., Sbaa, S., Pusca, R., Romary, R A. Comparative Study between the Adaptive Wavelet Transform and DWT Methods Applied to A Outer Raceway Fault Detection In Induction Motors Based on the Frequencies Analysis. In International Conference on Electrical Engineering, IEEE, Istanbul, Turkey, 2020; pp. 1-7. https://doi.org/10.1109/ICEE49691.2020.9249925 |
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. If left unaddressed, this defect can cause uneven contact between the rolling components and the raceway, resulting in increased vibrations and potential bearing failure. An inner race fault refers to damage or wear on the inner ring of the bearing, often caused by misalignment, heavy loading, or insufficient lubrication
. This damage interferes with the bearing’s smooth rotation, leading to uneven wear, elevated friction, and eventual failure. A ball fault involves damage to the rolling elements (balls) within the bearing, such as cracks, wear, or surface pitting
[20] | Toma, R. N., Prosvirin, A. E., Kim, J. M. Bearing Fault Diagnosis of Induction Motors Using A Genetic Algorithm and Machine Learning Classifiers. Sensors (Switzerland). 2020, 20(7), 1-19. https://doi.org/10.3390/s20071884 |
[20]
. This can result from improper lubrication, contamination, or excessive loads, leading to poor rolling contact and increased vibrations that can significantly reduce the lifespan of the bearing.
1.1.4. Rotor Eccentricity
When the centerline of a rotor deviates from its optimal position, rotor eccentricity occurs
[21] | Prudnikov, A. Y., Bonnet, V. V., Loginov, A. Y. Virtual Model of An Induction Motor With Rotor Eccentricity, In Institute of Physics Conference Series: Earth and Environmental Science, MDPI AG, Basel, Switzerland, 2020; pp. 1-6. https://doi.org/10.1088/1755-1315/548/3/032017 |
[21]
. This misalignment is a significant cause of vibration problems in induction motors. The resulting variation in rotor position leads to an uneven distribution of magnetic flux and an irregular air gap. As the rotor rotates, these inconsistencies generate vibrations that can adversely affect motor performance. Eventually, such vibrations can cause early wear on components, reduce efficiency, and, in severe cases, lead to catastrophic motor failure. There are various types of rotor eccentricity. The dynamic eccentricity involves a time-varying offset of the rotor's centerline
[22] | Archana, P., Praveen, K. N. Investigation of Dynamic Eccentricity in Switched Reluctance Motors: A Fusion of Finite Element Analysis and Machine Learning, In IEEE Control Instrumentation System Conference: Guiding Tomorrow: Emerging Trends in Control, Instrumentation, and Systems Engineering, IEEE, Manipal, India, 2024; pp. 1-6. https://doi.org/10.1109/CISCON62171.2024.10696578 |
[22]
. The static eccentricity refers to a constant, non-changing misalignment
[23] | Ma, C., Gao, Y., Degano, M., Wang, Y., Fang, J., Gerada, C., Zhou, S., Mu, Y. Eccentric Position Diagnosis of Static Eccentricity Fault of External Rotor Permanent Magnet Synchronous Motor As An In-Wheel Motor. IET Electric Power Applications. 2020, 14(11), 2037-2043. https://doi.org/10.1049/iet-epa.2019.0617 |
[23]
. Axial eccentricity is the offset along the rotor’s axis, while radial eccentricity involves an offset in the radial direction
[24] | Petryna, J., Duda, A., Sułowicz, M. Eccentricity In Induction Machines - A Useful Tool for Assessing Its Level. Energies. 2021, 14(7), 1-26. https://doi.org/10.3390/en14071976 |
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1.1.5. Stator and Rotor Core Damage
The stator and rotor cores are important components in induction motors, providing magnetic pathways for current flow
[25] | Marcolini, F., De-Donato, G., Capponi, F. G., Caricchi, F. A. Comparative Study of Stator Winding Technologies for Coreless Axial Flux Permanent Magnet Machines, In International Conference on Electrical Machines, IEEE Xplore, Torino, Italy, 2024; pp. 1-7. https://doi.org/10.1109/ICEM60801.2024.10700133 |
[25]
. Damage to theses cores can significantly disrupts the magnetic field, causing imbalance magnetic forces that lead to vibrations. The integrity of the stator and rotor cores can be compromised by several factors. Electrical issues, such as overheating, power surges, or poor insulation, can degrade core materials
[26] | Baraškova, T., Kudelina, K., Shirokova, V. New Opportunities in Real-Time Diagnostics of Induction Machines. Energies. 2024, 17(13), 1-16. https://doi.org/10.3390/en17133265 |
[26]
. Mechanical damage may result from impacts, excessive vibrations, or worn bearings. Also, environmental exposure including moisture or corrosive substances can lead to corrosion, further weakening the cores. Furthermore, normal wear and tear during motor operation also contributes to gradual degradation, increasing the risk of core-related faults and associated vibrations.
1.1.6. Loose and Worn-out Parts
Induction motor vibration can result from the deterioration of mechanical parts as the motor ages. As time passes by, components such as shafts, bearings, mountings, fasteners, and couplings may worn out or loosen, creating uneven stresses that lead to vibration
[27] | Borse, D., Tungikar, V. B., Patil, D. R. Failure Investigation of Induction Motor Bearing of Electric Vehicle Due to Manufacturing Defect, In International Conference on Advances in Materials Processing and Manufacturing Applications, Springer, Singapore, 2020; pp. 145-153. https://doi.org/10.1007/978-981-16-0909-1_15 |
[27]
. When these parts fail, the motor’s performance and integrity are compromised. The loosening and wear of motor parts are caused by several factors
[28] | Martin-Diaz, I., Garcia-Calva, T., Duque-Perez, Ó., Morinigo-Sotelo, D. Imbalanced Diagnosis Scheme for Incipient Rotor Faults in Inverter-Fed Induction Motors. Applied Sciences (Switzerland). 2024, 14(16), 1-15. https://doi.org/10.3390/app14167237 |
[28]
. Continuous operation gradually wears down parts, while overloading due to excessive mechanical or electrical demands further intensifies degradation. Poor maintenance practices, such as infrequent inspections or ignoring early warning signs, increases the likelihood of failure. Furthermore, environmental factors like temperature fluctuations, moisture, and corrosive substances can accelerate component wear. Manufacturing defects, such as the use of inferior materials or faulty construction, also contribute to premature failure.
1.1.7. Environmental Causes
Environmental conditions play a significant role in the vibration dynamics of induction motors and can greatly influence vibration-related issues
[29] | Choudhary, A., Jamwal, S., Goyal, D., Dang, R. K., Sehgal, S. Condition Monitoring of Induction Motor Using Internet of Things, In Proceedings of Recent Advances in Mechanical Engineering, Springer, Singapore, 2020; pp. 353-365. https://doi.org/10.1007/978-981-15-1071-7_30 |
[29]
. External factors such as resonance, mounting problems, and foundation defects can impose additional stress on the motor, resulting in unstable operation and increased vibration. One of the most critical environmental factors is the motor foundation
[30] | Jang, I. S., Kim, W. H. Study on Electromagnetic Vibration Analysis Process for Permanent Magnet Motors. IEEE Transactions on Applied Superconductivity. 2020, 30(4), pp. 1-6. https://doi.org/10.1109/TASC.2020.2976070 |
[30]
. Foundation issues can lead to misalignment, often caused by settling or movement of the foundation. A poorly designed foundation, lacking sufficient mass or rigidity, may exacerbate vibration problems by failing to properly absorb and dissipate mechanical energy. Neglected foundation integrity can result in cracks or shifts, further increasing vibration and compromising motor function.
1.2. Effects of Vibration on Induction Motors
1.2.1. Reduced Motor Efficiency
Vibrations negatively impact the conversion of mechanical energy into useful work, causing excessive energy loss in the form of heat. As friction increases, a greater portion of mechanical energy is dissipated as heat rather than contributing to productive output, directly reducing motor efficiency. This inefficiency not only impairs motor performance but also raises energy consumption, as more power is required to maintain the same output level. Several factors contribute to this reduced efficiency. One primary cause is increased friction between moving components, which generates heat and results in energy loss
[31] | Mousaei, A., Peng, H. A New Control Method for The Steadiness of Electric Vehicles With 2-Motor In Rear and Front Wheels. International Journal of Emerging Electric Power Systems. 2024, 25(4), 541-554. https://doi.org/10.1515/ijeeps-2023-0121 |
[31]
. Vibrations can also disrupt magnetic flux and current flow, leading to electrical losses that further degrade efficiency and increase operational costs
[32] | Ibragimov, M., Akbarov, D., Fayziyev, M., Beytullaeva, R., Nimatov, K., Safarov, K. S. Analysis of The Methods of Diagnosing Asynchronous Motors According To Vibration Indicators. IOP Conference Series: Earth and Environmental Science. 2023, 1142(1), 1-11. https://doi.org/10.1088/1755-1315/1142/1/012031 |
[32]
. Also, vibrations accelerate bearing wear, which in turn intensifies friction and amplifies energy loss
[33] | Noorazzmy, M. H., Sadiq, M. I., Sabri, M. A. M., Mohamed, I. F., Salleh, H., Muhalhal, H. A., Ghopa, W. A. W. Investigation of Vibrational Response of Bio-Lubricants and SAE40 for Journal Bearing Application. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences. 2024, 123(2), 214-230. https://doi.org/10.37934/arfmts.123.2.214230 |
[33]
. Worn bearings not only reduce efficiency but also increase maintenance requirements and the risk of equipment failure
[34] | Chen, Y., Zhang, H., Li, X., Xiao, S., Gu, F., Shi, Z. Effects of Wear on Lubrication Performance and Vibration Signatures of Rotor System Supported by Hydrodynamic Bearings. Lubricants. 2023, 11(3), 1-29. https://doi.org/10.3390/lubricants11030107 |
[34]
. Furthermore, uneven rotor movement caused by vibrations impairs energy transfer, compounding the inefficiency and escalating energy loss
[35] | Lee, H., Son, S., Jeong, D., Sun, K. H., Jeon, B. C., Oh, K. Y. A Finite Element Model of an Electric Motor with An Unbalanced Rotor for Vibration Data Generation. International Journal of Precision Engineering and Manufacturing-Smart Technology. 2024, 2(1), 47-56. https//doi.org/10.57062/ijpem-st.2023.0122 |
[35]
. These issues create a negative feedback loop, where rising vibration levels intensify the very conditions that caused them, leading to progressively worsening performance.
1.2.2. Increased Energy Consumption
In industrial environments, the increased energy consumption of induction motors due to vibration is a major concern. Vibration raises operational costs, lowers efficiency, and contributes to negative environmental impacts. It causes mechanical energy to be lost as heat rather than converted into useful work, further intensifying energy consumption and related economic challenges. Given the widespread reliance on induction motors, addressing this issue is necessary. Vibration-induced energy losses arise from both mechanical and electrical sources. Mechanically, vibrations generate friction between motor components, converting valuable mechanical energy into heat and reducing overall efficiency
[36] | Aguayo-Tapia, S., Avalos-Almazan, G., Rangel-Magdaleno, J. J., Ramirez-Cortes, J. M. Physical Variable Measurement Techniques for Fault Detection in Electric Motors. Energies. 2023, 16(12), 1-21. https://doi.org/10.3390/en16124780 |
[36]
. Electrically, vibrations cause fluctuations in magnetic flux and increase current flow, which further diminishes efficiency and raises energy usage
[37] | Mavlonov, J., Ruzimov, S., Tonoli, A., Amati, N., Mukhitdinov, A. Sensitivity Analysis of Electric Energy Consumption in Battery Electric Vehicles with Different Electric Motors. World Electric Vehicle Journal. 2023, 14(2), 1-16. https://doi.org/10.3390/wevj14020036 |
[37]
. These combined mechanical and electrical disturbances significantly impair performance, driving up energy consumption and highlighting the importance of effective vibration management.
1.2.3. Premature Wear and Tear
Vibration-induced damage in machinery can result in decreased motor reliability, increased maintenance costs, and reduced components lifespan. Gradually, vibrations cause wear and tear that considerably impacts the motor’s durability and efficiency. A number of factors contribute to vibration-induced early degradation. One of the causes is mechanical fatigue, triggered by repetitive stress cycles from continuous vibrations
[38] | Czerlunczakiewicz, E., Majerczak, M., Bonato, M. Fatigue Simulations for Automotive Components Undergoing Vibration Loadings: Effect of Nonlinear Behaviour. In Procedia Structural Integrity, Elsevier B.V., 2023; pp. 743-753. https://doi.org/10.1016/j.prostr.2024.03.080 |
[38]
. This stress gradually leads to material fatigue, often appearing as cracks that, if left unchecked, may result in catastrophic failure. In addition to fatigue, vibrations increase frictional wear. As components vibrate, friction increases, generating heat that accelerates deterioration. Excessive vibrations can also produce impact loads, which strike surfaces with force, causing further damage and faster wear of components. Another essential factor is lubrication breakdown. Vibrations disrupt the lubricant films essential for reducing friction and wear between moving parts
[39] | Morgan, W. J., Chu, H. Y. An Unsupervised Vibration Noise Reduction Approach and Its Application in Lubrication Condition Monitoring. Lubricants. 2023. 11(2), 1-20. https://doi.org/10.3390/lubricants11020090 |
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. As these films break down, friction increases, leading to faster component deterioration. Together, these factors create a vicious cycle of accelerated wear, posing significant risks to machinery performance and durability. Induction motor components are particularly vulnerable. Bearings, for example, wear out faster due to increased friction. Vibration can cause shaft deflection, elevating stress levels and promoting fatigue. Gears experience uneven loading and misalignment, leading to faster degradation. Seals also suffer under vibration stress, resulting in fluid leaks and contamination that compromise motor integrity.
1.2.4. Motor Failure
Vibration significantly affects the operational integrity of induction motors and can lead to a range of issues that may ultimately cause failure. One of the most critical consequences of vibration is bearing wear
[40] | Kobenkins, G., Rilevs, N. The Influence of Bearing Bore Wear on Power Indicators of the Traction Motor Gear Unit. In IEEE International Conference and Exposition On Electric and Power Engineering, Iasi, Romania, 2024; pp. 528-532. https://doi.org/10.1109/EPEi63510.2024.10758112 |
[40]
. Excessive vibration increases heat and friction. This accelerates bearing deterioration and leads to premature failure. Persistent vibration also degrades motor winding insulation, increasing the risk of short circuit or ground faults that can impair performance. Furthermore, vibration induces mechanical stress on components such as the rotor, stator, and shaft
[41] | Horváth, K., Zelei, A. Simulating Noise, Vibration, and Harshness Advances in Electric Vehicle Powertrains: Strategies and Challenges. World Electric Vehicle Journal. 2024, 15(8), 1-17. https://doi.org/10.3390/wevj15080367 |
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, potentially causing material fatigue and structural failure. Long-term vibration may cause misalignment between the motor and the connected equipment, further increasing wear and reducing efficiency. Furthermore, it can loosen electrical connections, leading to overheating, intermittent contact or short circuits, and increased resistance.
1.2.5. Noise Pollution
Vibration is closely linked to noise pollution, a growing environmental concern. Noise pollution refers to excessive or unwanted sound that disrupts the environment, and it encompasses more than just loudness
. Its impact depends on several factors, including frequency, duration, and unpredictability. As its core, noise is a manifestation of vibration. Sound waves are vibrations transmitted through materials such as water or air. When object vibrates, it causes surrounding air particles to move, producing sound waves perceived as noise. This fundamental relationship explains why many sources of vibration inevitably contribute to noise pollution. Vibration-induced noise is generated by a range of everyday and industrial activities. Industrial machinery such as the heavy duty motors used in factories or construction sites produce large vibrations that are audible as noise
[43] | Hassan, I. U., Panduru, K., Walsh, J. An In-Depth Study of Vibration Sensors for Condition Monitoring. Sensors. 2024, 24(3), 1-33. https://doi.org/10.3390/s24030740 |
[43]
. Similarly, transportation systems like cars, trains, and airplanes contribute to noise pollution both directly and by causing nearby structures to vibrate. Common building systems also play a role. Heating, Ventilation, and Air Conditioning (HVAC) units, elevators, and plumbing can generate significant indoor noise due to vibration.
1.2.6. Structural Damage
Induction motors are well known for their reliability and efficiency in industrial applications. However, they inevitably generate vibrations during operation. While some vibration is normal, if left unmanaged, can significantly compromise the structural integrity of the motor. Vibrations in induction motors can lead to various forms of structural damage
[44] | Seventekidis, P., Karyofyllas, G., Giagopoulos, D., Parametric Study on Structural Damage Classification with Numerically Simulated Vibration Data. Journal of Physics: Conference Series. 2024, 2647(2), 1-8. https://doi.org/10.1088/1742-6596/2647/2/022004 |
[44]
. Repeated vibration cycles can cause wear on structural components, resulting in cracks that may expand over time. Vibrations may also loosen bolts, welds, and other fasteners, weakening the entire assembly. Also, continuous vibration speeds up material fatigue and degradation, increasing the risk of premature failure. One particularly critical issue is resonance, which occurs when the motor’s operating frequency matches the natural frequency of its supporting structure, amplifying vibrations to potentially dangerous levels
[45] | Kang, H., Kook, J., Lee, J., Kim, Y. K. A Novel Small-Scale Bladeless Wind Turbine Using Vortex-Induced Vibration and a Discrete Resonance-Shifting Module. Applied Sciences (Switzerland). 2024, 14(18), 1-16. https://doi.org/10.3390/app14188217 |
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1.3. Related Works on Vibration-induced Thermal Analysis in Induction Motors
The impact of magnetic and mechanical rotor eccentricity on induction motor vibration was examined by
[46] | Goroshko, A. V., Zembytska, M. V., Paiuk, V. P. Induction Motor Vibrations Caused by Mechanical and Magnetic Rotor Eccentricity. Journal of Engineering Sciences. 2024, 10(1), 66-77. https://doi.org/10.21272/jes.2024.11(1).d8 |
[46]
, revealing links to excessive heating, reduced performance, and bearing failures. Eccentricity-induced vibrations were common across sectors, accelerating wear and shortening motor lifespan. A mathematical model incorporating magnetic eccentricity, rotor offset, and gyroscopic forces was developed to predict and mitigate vibration-related heating. The study emphasised aligning rotor angles to reduce static eccentricity and proposed early detection and monitoring as key strategies to prevent motor defects.
Advanced methods to reduce vibration-induced heating in induction motors using Finite Element Approach (FEA), Experimental Modal Technique (EMT), and Vibrational Analysis (VA) was investigated by
[47] | Sri, R. P., Kapu, V., Dhananjay, R. K., Alsaif, F. Induction Motor Structure Design to Reduce Vibrations with Numerical (FEA) and Experimental (VA) Techniques. IEEE Access. 2024, 12(1), 40894-40904. https://doi.org/10.1109/ACCESS.2024.3374785 |
[47]
. These techniques were used to detect structural distortions, predict vibration velocity, and minimise friction buildup. The study emphasised identifying vibration sources and making structural adjustments to improve thermal management, reliability, and durability.
Dahifale highlighted the role of vibration analysis in diagnosing failures in three-phase induction motors
[48] | Dahifale, V., Keskar, M., Kakyalia, V., Rodge, S., Karve, G. M. Fault Detection of 3-Phase Induction Motor Using Vibration Analysis. International Journal For Multidisciplinary Research. 2023, 5(5). 1-9. https://doi.org/10.36948/ijfmr |
[48]
. Vibration was identified as a key cause of overheating, friction, mechanical stress, and reduced efficiency. Factors such as overloading, single-phasing, and bearing defects contributed to high vibration levels, leading to wear, bearing failures, and safety risks. The study stressed the need for advanced vibration analysis methods such as frequency spectrum and motor analysis to detect issues early, prevent overheating, and reduce downtime.
The impact of harmonic currents on vibration, electromagnetic force, and noise in permanent magnet synchronous motors for electric vehicles were performed by
[49] | Wang, L., Wang, X., Li, N. and Li, T. Modelling and Analysis of Electromagnetic Force, Vibration, and Noise In Permanent Magnet Synchronous Motor for Electric Vehicles Under Different Working Conditions Considering Current Harmonics. IET Electric Power Applications. 2023, 17(7), 952-964. https://doi.org/10.1049/elp2.12315 |
[49]
. The study found that harmonic induced vibrations significantly contributed to overheating by increasing friction, mechanical stress, and heat generation. These effects led to reduced efficiency, premature wear, demagnetisation, and bearing failures. The study underscored the importance of controlling harmonic currents and minimising vibration to maintain the reliability, efficiency, and thermally stable operation of Permanent Magnet Synchronous Motors (PMSMs) in electric vehicles.
The use of vibration signals to diagnose induction motors faults, identifying vibration as a key cause of overheating was examined by
[50] | Liu, X., Hong, J., Zhao, K., Sun, B., Zhang, W., Jiang, J. Vibration Analysis for Fault Diagnosis in Induction Motors Using One-Dimensional Dilated Convolutional Neural Networks. Machines. 2023, 11(12), 1-17. https://doi.org/10.3390/machines11121061 |
[50]
. Faults, such as broken rotor bars and rotor eccentricity increased friction, leading to excessive heating, mechanical stress, and reduced efficiency. The study also analysed electromagnetic forces under normal and faulty conditions. To address these issues, the researchers developed a fault diagnosis system using a One-Dimensional Dilated Convolutional Neural Network (1D-DCNN). This system enabled early fault detection and intervention, helping to prevent overheating, reduce downtime, and maintain safe, continuous motor operation.
Impact of unbalanced voltage on IMs across different efficiency classes was investigated by
[51] | Donolo, P., Pezzani, C., Bossio, G., de-Angelo, C., Donolo, M. Vibration Magnitude Analysis on Induction Motors of Different Efficiency Classes Due to Voltage Unbalance. IEEE Transactions on Industry Applications. 2023, 59(3), 2913-2918. https://doi.org/10.1109/TIA.2023.3237218 |
[51]
. The study found that higher-efficiency IMs experienced more pronounced vibrations, leading to increased friction, heat generation, and mechanical stress. Mathematical models were developed to predict active power under unbalanced voltage conditions, and results were validated through simulations and laboratory tests. Compared with industry vibration standards, findings indicated that high efficiency IMs are more vulnerable to vibration-related issues. The researchers recommended implementing protection mechanisms to prevent overheating and highlighted the importance of addressing voltage unbalance to ensure reliable motor operation.
The effects of magnetic vibrations on squirrel-cage induction motor stators, linking them to supply voltage distortion was examined by
[52] | Ermolaev, A., Erofeev, V., Plekhov, A., Titov, D. Magnetic Vibration in Induction Motor Caused by Supply Voltage Distortion. Energies. 2022, 15(24), 1-11. https://doi.org/10.3390/en15249600 |
[52]
. These vibrations increased friction, causing excessive hating, mechanical stress, and reduced efficiency. They researchers proposed a mathematical model of the excitation process and used finite element software to simulate motor behaviour under distorted voltage. The results showed that magnetic vibrations also elevated power consumption and acoustic noise. The study emphasised the importance of combining acoustic, mechanical, and electromagnetic analysis, especially for medium and high power alternating current motors, to better understand and reduce vibration-induced heating.
Prasad and Singh investigated the link between excessive heating and vibration-induced resonance in ageing induction motors
[53] | Prasad, K. V. S. R., Singh, V. Numerical Investigation and Experimental Modal Analysis Validation to Mitigate Vibration of Induction Machine Caused due to Electrical and Mechanical Faults. Journal of Electrical Engineering and Technology. 2022, 17(4), 2259-2273. https://doi.org/10.1007/s42835-022-01049-8 |
[53]
. Mechanical issues like misalignment and wear were identified as key sources of vibration, leading to increase friction, mechanical stress, and heat generation. This heat caused electrical faults, insulation breakdown, and overheating, resulting in reduced efficiency, winding damage, and bearing failure To address these issues, the researchers developed numerical and experimental methods to detect and mitigate both electrical and mechanical faults.
Vibration characteristics of a 1140 V/75 kW variable-frequency motor, revealing that vibration was a major cause of overheating was explored by
[54] | Su, Z., Luo, L., Liu, J., Li, Z., Luo, H., Bai, H. Research on Vibration and Noise of Induction Motor under Variable Frequency. Symmetry. 2022, 14(3), 1-19. https://doi.org/10.3390/sym14030569 |
[54]
. Factors such as temperature fluctuations, magnetostriction of silicon steel sheets, and frequency variation increased electromagnetic forces and energy losses. This led to excessive heating, reducing motor efficiency and performance. Vibration-induced stress, friction, and heat accelerated component wear, causing insulation failure, winding damage, and bearing issues. These issues resulted in premature ageing, increased maintenance costs, and frequent breakdowns. The study emphasised the role of controlling vibration to prevent overheating and ensure reliable motor operation.
A structured method to assess vibration frequency components for detecting bearing faults was presented by
[55] | Tabasi, M., Ojaghi, M., Mostafavi, M. Vibration Analysis As Useful Domain for Detection of Bearing Fault Signals In Induction Motors. International Journal of Engineering, Transactions B: Applications. 2021, 34(8), 2010–2020. https://doi.org/10.5829/ije.2021.34.08b.22 |
[55]
. The study found that vibration-induced friction and mechanical stress generated heat, leading to premature motor wear, reduced efficiency, and a higher risk of failure. Vibration analysis played a key role in identifying early signs of misalignment and bearing issues, enabling timely corrective actions to prevent overheating and minimise energy loss. The researchers also offered practical guidelines for implementing vibration-based monitoring in industrial settings, including optimal measurement directions and frequency ranges for detecting specific faults.
Gundewar and Kane
reviewed diagnostic techniques for identifying faults in induction motors, highlighting vibration as a contributor to excessive heating. Vibration-induced issues such as misalignment, imbalance, and bearing faults, led to friction, mechanical stress, and heat buildup. The study highlighted both conventional and advanced methods, including vibration-based diagnostics and motor current signature analysis. It also explored AI-based techniques such as Genetic Algorithm (GA), Adaptive Neuro-Fuzzy Inference System (ANFIS), Artificial Neural Network (ANN), Support Vector Machine (SVM), and Fuzzy Logic (FL). The importance of condition monitoring was stressed, especially in electric vehicles, where vibration related faults can cause early wear, reduce efficiency, and system unreliability. Effective diagnostics were deemed vital for minimising downtime.
The behaviour of stator end windings in induction motors was analysed with a focus on vibration as a cause of excessive heating
[57] | Prasad, K. V. S. R., Singh, V. Looseness Identification of Stator End Windings of Induction Motor By Modal Test. In IEEE International Conference on Power Electronics, Drives and Energy Systems, Jaipur, India. 2020; pp. 1-5. https://doi.org/10.1109/PEDES49360.2020.9379438 |
[57]
. This heating increases the risk of motor failure, early wear, and reduced efficiency. The study emphasised the need to detect vibrations in the end windings to prevent damage caused by friction, mechanical stress, and heat. Structural analysis and impact tests revealed that looseness in the stator end windings intensified vibration heat generation. The findings highlighted the importance of secure winding structures to enhance motor reliability and thermal stability.
A study to
monitor the health of induction motor bearings for early fault detection, aiming to reduce accidents and economic losses was performed by
[58] | Xu, M., Feng, G., He, Q., Gu, F. and Ball, A. Vibration Characteristics of Rolling Element Bearings With Different Radial Clearances for Condition Monitoring of Wind Turbine. Applied Sciences (Switzerland). 2020, 10(14), pp. 1-19. https://doi.org/10.3390/app10144731 |
[58]
. They developed a nonlinear vibration model with six degrees of freedom to analyse bearing behaviour under varying load conditions and radial clearances. The study proposed key indicators for tracking clearance angles, which were essential for effective maintenance and condition monitoring. These findings were relevant in wind turbine systems, where vibration-induced faults can lead reduced efficiency, premature bearing wear, and an increased risk of system failure due to overheating.
A system to predict and reduce vibration in Switched Reluctance Motors (SRMs), addressing vibration-induced issues such as misalignment, imbalance, and bearing faults was developed by
[59] | Ling, X., Tao, J., Li, B., Qin, C., Liu, C. A Multi-physics Modeling-Based Vibration Prediction Method for Switched Reluctance Motors. Applied Sciences (Switzerland), 2019, 9(21), pp. 1-16. https://doi.org/10.3390/app9214544 |
[59]
. The approach integrated three modules. That were, a digital controller and drive circuit, electromagnetic field, and mechanical components. The system enabled real-time vibration prediction and monitoring by combining electromagnetic forces with the structural model. Tested on a 12/8 poles, 1.5 kW SRM drive system test bench, the method aligned with experimental results. It allowed for optimised structural design and control strategies, helping to minimise vibration-induced faults, improve efficiency, and enhance the reliability of SRMs.
The study by
[60] | Zeng, D., Zou, J., Xu, Y. Analysis for the Vibration Characteristics of The Induction Machine In Different Operating Status, In 22nd International Conference on Electrical Machines and Systems, Harbin, China, 2019; pp. 1–5. https://doi.org/10.1109/ICEMS.2019.8922317 |
[60]
examined how vibration levels in induction motors vary under different operating conditions, such as speed and load. It found that excessive vibrations amplified electromagnetic forces, leading to significant heat generation and thermal issues. These problems were further aggravated by harmonic distortions in electrical signals, largely influenced by Pulse Width Modulation (PWM) frequency in inverters. The interaction between electromagnetic forces, vibrations, and signal harmonics created a feedback loop of overheating. This cycle eventually reduced the efficiency of the motors, increased the risks of damage, and shortened their lifespan.
A comprehensive method for detecting bearing faults, introducing envelope analysis to classify current spectrum anomalies linked to localised faults was presented by
[61] | Areias, I. A. D.S., Borges da Silva, L. E., Bonaldi, E. L., de Lacerda de Oliveira, L. E., Lambert-Torres, G., Bernardes, V. A. Evaluation of Current Signature In Bearing Defects By Envelope Analysis of The Vibration In Induction Motors. Energies. 2019, 12(21), pp 1-15. https://doi.org/10.3390/en12214029 |
[61]
. This technique was tested on both operational and non-operational motors in a laboratory setting. The system enabled real-time data acquisition and fault diagnosis by integrating the results with vibration analysis and single board computer technology. This study identified vibration as a cause of excessive heating in induction motors.
2. Methodology
2.1. Design of an Autoencoder-based Fault
Classification System
Artificial Neural Network (ANN) can handle multivariable interactions, model complex relationships, and learn from data. In this study, an ANN was applied to thermal analysis of an induction motor, with vibration considered as the primary causal factor. This approach enabled precise predictions of thermal behaviour and abnormal detection. The ANN model was developed through a series of systematic steps as depicted in
figure 3.
Figure 3. ANN-based Autoencoder System Design.
2.1.1. Data Cleaning
The vibration data was cleaned by removing duplicates, inconsistencies, and errors to ensure accuracy. This step was important, as even minor irregularities could compromise data integrity and hinder effective machine learning model training.
2.1.2. Feature Scaling
Min-max normalization was applied to scale feature between 0 and 1, ensuring all input variables contributed equally to the learning process. The normalisation formula is based on:
(1) where

is the new normalised value, typically between 0 and 1,

is the original value of the feature before scaling,

is the minimum value of the feature in the dataset, and

is the maximum value of the feature in the dataset.
2.1.3. Time-series Reshaping
To capture temporal dependencies, the data was structured into overlapping time windows. A sliding window approach was used to train the model with sequences of past observations, enabling it to learn trends and patterns over time.
2.1.4. Splitting Data for Training and Testing
The dataset was split into training and test sets. The training set included only normal (healthy) machine operations to help the autoencoder learn typical behaviour, while the test set contained both normal and faulty conditions to evaluate the model’s ability to detect anomalies.
2.2. Development of the Autoencoder Model
The autoencoder was implemented using TensorFlow and Keras. Its architecture included defined hidden layers, neurons, optimisation methods, loss functions, and activation functions. The AE enabled unsupervised learning by compressing data and extracting high-level features for deep model development.
2.2.1. Autoencoder Architecture
The architecture of the AE as shown in
figure 4 was adopted from
[62] | Berahmand, K., Daneshfar, F., Salehi, E.S., Li, Y., Xu, Y., 2024. Autoencoders and their applications in machine learning: a survey. Artificial Intelligence Review, 57(2), p. 1-52. https://doi.org/10.1007/s10462-023-10662-6 |
[62]
, where X stands for the input layer's data, Z for the hidden layer's data, and Xˈ for the output layer's reconstructed output data. The encoder and the decoder are the two main parts of the AE. The input data is compressed into a lower-dimensional latent representation, which is then used by the decoder to recreate the original data.
Figure 4. Autoencoder Architecture.
An AE uses an encoding function f to translate an input vector X to a code vector Z during the encoding step. The decoding stage converts the coding vector Z back to the output vector X so that the input data can be rebuilt using a decoding function g. Through minimising the reconstruction error (L) between X and the reconstructed data

, AEs fine-tune the network's weights (W). To optimise the network's settings, this reconstruction error serves as a loss function. The objective function of the AE can be written as follows:
(2) where n is the total number of training data points,

represents the ith dimension of the output data, and

represents the ith dimension of the training sample. The reconstruction error (L) between the input and output data is given as:
(3) The mapping function for the encoder is expressed as:
(4) where s is an activation function, b is the bias factor, W is the weight matrix, and x is the input vector. Also, the mapping function for the decoder that performs the inverse operation is expressed as:
(5) where s represents the activation function (ReLU or sigmoid), W′ represents the decoder's weight matrix, b′ represents the decoder's bias vector, z represents the reconstructed form of the original input vector x, and y represents the encoder's compressed representation.
2.2.2. Training Parameters of the Vibration-based Autoencoder
Training parameters for the autoencoder model used in vibration-based thermal detection and optimisation were carefully selected and customised for optimal performance, as shown in
Table 1.
Table 1. Training Parameters of the Autoencoder Model.
Parameters | Vibration-based Autoencoder |
Optimiser | Adam |
Initial Learning Rate | 0.00100 |
Final Learning Rate | 0.00005 |
Batch Size | 128 |
Regularisation Term (L2) | 0.00050 |
Epochs Trained | 30 |
Best Validation Loss | 0.01020 |
Gradient at Last Epoch | 0.00021 |
2.2.3. Loss Function and Optimisation Algorithm
The loss function was minimised using the Adam optimiser. Reconstruction loss was calculated using the Mean Squared Error (MSE) as follows;
(6) where n is the number of data points or observations being considered,
is the original (true) value of the ith data point,
is the predicted or reconstructed value of the ith data point by the model,
is the squared difference between the actual and predicted values, and

is the summation over all nth data points to compute the total squared error, and the inverse of n is the average of the total squared error, giving the mean squared error.
2.3. Training of the Vibration Autoencoder Model
2.3.1. Training of the Vibration-based Autoencoder
The AE was trained on the preprocessed vibration datasets. The data was normalised between 0 and 1 using Min-max scaling to ensure consistency as:
(7) where max (x) and min (x) stand for the feature x's maximum and minimum values, respectively. The model was trained over 30 epochs with a batch size of 128, using 80% of the data for training.
2.3.2. Evaluation During Training
The reconstruction loss (MSE) was monitored during training to evaluate model performance. Early stopping was applied to halt training when validation loss ceased to improve for 10 consecutive epochs to avoid overfitting.
2.4. Validation and Testing of the Vibration-based Autoencoder Model
2.4.1. Validation Strategy and Metrics
Validation was performed on 20% of the dataset to assess generalisation capability. The Mean Squared Error (MSE) was used as the primary metric. Additionally, accuracy and F1 score were computed after thresholding the reconstruction error to classify fault vs. normal conditions.
2.4.2. Testing with Unseen Data
To evaluate the robustness of the model, it was tested with unseen data containing various fault scenarios in the induction motor. The model successfully identified anomalies based on reconstruction errors above a pre-defined threshold.
2.5. Vibration-based Autoencoder Model Implementation and Programming
2.5.1. Tools, Libraries, and Environment Setup
The environment was set up using Anaconda and executed on a machine with GPU acceleration. The implementation was carried out in Python using the following libraries:
1) TensorFlow 2.x’; and
2) Keras.
2.5.2. Code Structure and Workflow Overview
The codebase was structured into the following modules:
1) data_preprocessing.py: normalization and reshaping of time-series data;
2) autoencoder_model.py: definition of the encoder, decoder, and full autoencoder;
3) train_model.py: training loop, early stopping, and model checkpointing; and
4) evaluate_model.py: reconstruction error analysis and visualisation.
2.5.3. Exploratory Data Analysis
The Exploratory Data Analysis (EDA) was used to identify patterns, anomalies, and relationships within the dataset to detect deviations and faults, and guide preprocessing and modelling strategies.