Electric motors are essential for countless companies across hundreds of different industries. While production shutdowns for routine maintenance can be scheduled to minimize downtime and lost productivity, unexpected electric motor repairs or replacements can bring your business to a screeching halt.
Overheating is the most common cause of electric motor failure. Electrical and mechanical issues can generate excessive heat, affecting every internal motor component. To help keep your electric motors running at peak performance and to improve your uptime, here are the five most common causes of electric motor failure.
1. Electric Motor Contamination
Potential contaminants are everywhere. Dust and dirt build-up at lubrication points is typical, but left unchecked, it can eventually work past seals and gaskets to damage rotating internal components. Excessive dirt buildup on the motor exterior and cooling fins acts as insulation to further raise internal operating temperatures.
Condensation and moisture can contaminate the electric motor’s grease or oil supply, which lubricates internals and transfers heat. Other chemicals, fluids, and additives can adversely impact the seals or gaskets that protect the motor from outside contaminants.
2. Excessive Motor Vibrations
While all electric motors utilize rotating components, excessive vibrations can increase operating temperatures, resulting in premature wear, damage, and electric motor failure. These vibrations can result from an improper initial installation, such as parallel or angular soft foot, where the mounting feet or mounting surface are uneven.
3. Misaligned Shafts
Misalignment between the motor shaft and load or connected shafts can result in excessive vibrations, generating more heat. While it’s impossible to eliminate all motor imbalances, regular testing, and monitoring will indicate when the imbalance exceeds manufacturer recommendations.
Contrary to popular belief, a flexible coupling only prevents the coupling connection from misalignment. It does not correct, eliminate, or compensate for shaft misalignment issues. With a misaligned shaft, the constant cyclical force damage travels along the shaft and back to the motor, generating even more heat while increasing mechanical load.
4. Voltage Imbalance
Three-phase distribution systems typically serve single-phase loads or equipment. As a result, all three phases of voltage should have the same magnitude. A voltage imbalance can result from either impedance or unequal load distribution. These imbalances can occur:
- In the motor cabling
- Within the motor windings
- When motor connections are loose, corroded, or damaged
Any of these issues can create an imbalance, which can cause stress, higher operating temperatures, or insulation breakdown in the phase circuits used in a three-phase power system.
5. Transient Voltage
Transient voltages can also be problematic since they can originate from sources inside or outside the physical location.
- Adjacent load cycling
- Local/distant weather
- Power factor correction capacitor banks
These transients vary in amplitude and frequency and can erode or cause insulation breakdown in motor windings. Tracking down these transients is more difficult because they appear intermittently and can present themselves in various fashions. For example, a transient can appear on the control cables that don’t cause direct equipment damage but could ultimately disrupt operations and production lines.
Low resistance is the most common cause of electric motor failure, caused by the cumulative damage from these five common causes. Leading standardization organizations have concluded that 30 percent of motor failures are attributed to insulation failure, and 60 percent are caused by overheating issues. The standard rule states that insulation life decreases by 50% for every 10°C of additional heat to the windings. To put that into an operations perspective, an electric motor that typically lasts 20 years of regular service, running at 40° C above its rated temperature, would only last one year.
The good news is that two simple tools—regular inspections and proper maintenance—can prevent most electric motor failures caused by the above-mentioned issues. To keep you up and running, Hi-Speed offers the following services to keep your electric motors running at peak performance.
- Instrument calibration
- Mechanical measurements
- Core testing and rewinding
- Bearing replacement and lubrication
- Bearing fit rebuilding
- Electrical testing
You can email the Hi-Speed Electric Motor Experts or call us at 800-713-0103 to learn more about these services or to discuss a regular testing and inspection process. For additional information regarding electric motor repairs, check out this recent Hi-Speed blog post or this industry standard, ANSI/EASA Standard AR100-2020: Recommended Practice for the Repair of Rotating Electrical Apparatus.