Organisations looking to give their motors a new lease on life rely on electric motor rewinds and motor diagnostics to restore their machinery back to its original condition, provided its essential components like the stator, rotor, and laminations remain intact. As a refresher, rewinding is the process of removing all the windings from a motor, which are essentially wires placed within its stator or armature. This component is responsible for generating a magnetic field that drives the rotors of the motor and ultimately makes it work. Once all the old windings are stripped away, a fresh set of windings takes their place which will be rewound through the stator followed by a final insulation procedure. While motor rewinds are commonly associated with restoring the efficiency and extending the lifespan of ageing motors, they also help address several motor-failure-related issues in the process.
Read on as we go over what else rewinding can help with beyond efficiency and performance restoration.
1. Low Insulation Resistance
Low insulation resistance is one of the most common reasons why motors run into failure, and it is largely caused by the winding insulation becoming degraded due to various factors like corrosion, overheating, or physical damage. Insulation serves to keep the heat within the motor unit under control, and a low resistance means there is not enough isolation between the windings and conductors. Leakages and short circuits then follow as a result, as well as other issues like reduced lubrication stemming from high heat that puts various motor components at a high risk of damage. All these issues eventually result in motor failure.
That said, encountering insulation resistance issues are part and parcel of an electric motor’s service life because of the prolonged exposure to contaminants, vibration, erratic power surges, or foreign objects over years of operations. It is therefore fortunate that rewinding can help solve it with ease and subsequently address the problems associated with it.
2. Phase Imbalance and Voltage Issues
When motors operate under unbalanced electrical phases or with incorrect voltage levels, the winding coils experience stress and degrade more quickly. Such conditions result in overheating and internal faults. Motors designed to operate on three-phase power rely on equal voltage distribution across all phases to function efficiently. When one or more phases carry less voltage than the others—or if the voltage deviates from the required specification—the motor becomes strained, leading to excessive heat buildup and inefficiencies. This phase imbalance forces the motor to draw more current than necessary, accelerating the degradation of the winding insulation and shortening the motor’s lifespan.
3. Operational Overloads and Overheating
Excessive heat is one of the biggest reasons why motors fail, and this almost always occurs because of overloading. Overloads happen when an electric motor draws too much current due to mechanical, electrical, or load-related issues, ultimately causing it to run hotter than normal. If a motor is left to operate under high heat for a prolonged period, key parts like its winding insulation will experience rapid deterioration and inevitably experience leakages, short-circuiting, and motor failure.
The common rule regarding motor operational temperatures is that the insulation’s lifespan gets cut in half for every additional 10°C of heat the windings experience. Apart from overloads, a motor’s start up phase can also cause overheating as a unit typically draws up to eight times its rated current, increasing its thermal status and subjecting the windings to excessive thermal stress that contributes to motor failure.
4. Strange Noises or Vibrations
Electric motors are designed to operate smoothly with minimal noise and vibration. When unusual sounds—such as grinding, humming, or buzzing—arise, or if there is excessive vibration, it’s a clear sign that the motor is experiencing mechanical or electrical issues. These disturbances can stem from multiple factors, such as worn bearings, misalignment, rotor imbalance, or damaged windings.
Common Causes of Noise and Vibration:
- Worn Bearings: Bearings support the rotating shaft within the motor. Over time, they can wear down or become contaminated with dirt and debris, leading to grinding noises and friction-related vibration.
- Misalignment: If the motor shaft or components aren’t aligned correctly due to poor electric motor installation, the resulting imbalance can cause excessive vibration and abnormal wear on parts, potentially damaging windings or other components.
- Rotor Imbalance: When the rotor is not evenly balanced, it can lead to uneven rotation, creating noise and vibrations that stress the motor over time. This imbalance might occur due to bent shafts or uneven material distribution.
- Loose or Damaged Windings: If windings have become loose or damaged, they may produce a buzzing or humming sound, as the magnetic field is no longer stable. This can also cause abnormal vibration, indicating internal issues that require immediate attention.
When vibrations or strange noises are traced back to winding damage, rewinding can help resolve such issues. Proper rewinding also ensures that the windings are tightly secured, minimizing the chances of future movement that could generate unwanted vibrations.
Conclusion
Electric motor rewinding plays a critical role in addressing several common failure issues that would otherwise compromise a motor’s performance and longevity. From restoring degraded insulation resistance to mitigating voltage imbalances and resolving winding-related noise or vibration problems, rewinding ensures motors can continue to function efficiently. Additionally, it helps prevent mechanical damage caused by overheating and overloads, extending the operational life of the motor. By identifying and correcting these issues through proper rewinding techniques, businesses can avoid costly replacements, reduce downtime, and enhance the reliability of their equipment.
