Electric Motor Failure

Industrial electric motor systems have become more complicated, so when malfunctions occur, it is not always easy to identify the cause. Motor failure may be caused by mechanical or electrical problems, especially if the motor is improperly sized, installed, or maintained. Understanding the most common causes of motor failure can help you prioritize preventative maintenance and prevent costly downtime. 

Transient Voltage

Transient voltage refers to short power surges from either internal sources, such as static discharge, or external sources, such as lightning or shared transformers. These surges vary in amplitude and frequency, and because of their variability and uncommonness, it can be difficult to identify the source of the problem. Transients force motors to overheat and interfere with timing. Over time, exposure to transients can degrade motor winding, leading to complete motor failure. 

If it is impossible to remove the source of the transient voltage, such as when it is coming from external sources, transient surge suppressors may help level the voltage entering the motor to prevent damage. 

Reflections on Drive Output PWM Signals

Variable-frequency drives use a technique known as pulse width modulation (PWM) to synthesize the motor’s output. When installed or maintained improperly, these devices produce reflections, meaning that some of the signal travels back to the origin. These reflections cause impedance mismatches and produce strain on the motor winding insulation, resulting in motor failure.

Overload and Overheating

One of the simplest causes of motor failure is overload, which occurs when you exceed a motor’s capacity, resulting in overheating and excess current draw. Motor overload causes both mechanical and electrical damage, inducing premature wear and degradation of the motor winding insulation. These effects can be prevented by properly sizing the motor to the driven load.


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Misalignment is another common cause of motor failure that is rooted in improper setup. Misalignment occurs when the drive shaft does not line up with the load, causing harmful vibrations that wear down the motor. Different types of misalignment include:

  • Angular
  • Parallel
  • Compound
  • Rotating looseness
  • Non-rotating looseness

Any of these misalignments can cause motor failure as they wear down system components, but they can all be prevented by ensuring that the drive shaft is always properly aligned with the load before operation.


Imbalance is similar to misalignment in that it involves a simple mechanical inefficiency that compounds into serious damage over time. Imbalances occur when mass is unevenly distributed around an axis of rotation, which can happen in a number of circumstances, including:

  • Improper installation
  • Dirt or rust build-up
  • Faulty components
  • Missing or missized balance weights

Preventative maintenance is key to spotting and fixing imbalances before they ruin a motor.

Laser Alignment & Balancing

Bearing Wear

Bearing wear is another isolated mechanical failure that cascades into more serious damage. Failed bearings are less efficient and emit more heat than functional bearings, forcing additional strain on functional components, which are then at higher risk of failure themselves. Bearings can fail for any number of reasons, including:

  • Overloading
  • Improper lubrication
  • Shaft misalignment
  • Improper installation

Bearings can also fail due to normal wear and tear. Your regular maintenance routine should include inspections to verify bearing integrity and replace those that show signs of deterioration. Otherwise, a single failed bearing can quickly become a completely failing motor.

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Renown Electric: Maintenance & Repair for Industrial Motors

Motor failure can occur despite your best intentions due to either errors or normal wear and tear. Regardless of the cause, downtime is expensive, so it’s critical to have a repair shop that you can trust. Renown Electric offers comprehensive shop services to diagnose and repair motor problems of all kinds, drawing on computerized testing and leading repair equipment to quickly return motors to OEM standards. Our professional staff is on hand 24/7 to help troubleshoot so you can get up and running as soon as possible. 

As an ISO 9001:2015-certified company, we take pride in the quality of our repairs, and clients have trusted our services for over 30 years. In addition to repair services, we also work with clients to develop personalized preventative maintenance protocols tailored to their unique needs. Our shop offers extensive on-site testing capabilities for advanced diagnostics, and we draw on custom system analyses to inform our preventative and predictive maintenance recommendations. 

With our affordable maintenance services, you can protect your facility from the costly downtime and replacements associated with motor breakdown. To learn how Renown Electric can help you prevent motor failure, repair damaged systems, and maximize your efficiency and bottom-line, please contact us today.

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