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Common Causes of Electrical Motor Failure

Posted on by Matt Passannante

Electric motors can fail for many reasons. Motors have an average lifespan of 30,000 – 40,000 hours, which depends largely on maintenance. Motors that stop functioning can bring your operations to a halt, along with causing downtime and lost revenue. They can also be a safety hazard. If your electric motors are not working properly, these clues can help you pinpoint the problem.

Low Resistance

Low resistance is one of the most common causes of failures in electrical motors. It can also be one of the most challenging problems to fix. Low resistance is caused by a breakdown in the insulation in the windings from physical damage, corrosion, and overheating. The resulting insufficient isolation can cause shortages and leaks. The insulation should be inspected and replaced when necessary.

Electrical Overload

Electrical overload is attributed to excessive current flow in the motor’s windings. An overload, or over-current, exceeds the design current that the electrical motor can safely and efficiently tolerate. The overload is generally caused by a low voltage supply, which causes the motor to draw in more current in an effort to maintain the same torque output. An overload can also be caused by a short circuit in the conductors or if there is an excessive voltage supply. This problem may be resolved by installing an over-current protection that detects an over-current when it starts and stops power supply.


Overheating is a common cause of failure in electrical motors. It accounts for about 55% of all insulating failures in electrical motors. Overheating is attributed to several possible causes, including a high temperature operating environment or poor power quality. The insulation life is quickly reduced by 50% for every 10oc temperature increase in a motor. Motors should be kept as cool as possible to avoid breakdowns.


Contamination can be due to dirt, dust, and chemicals. Regardless of the source, it’s a main cause of motor failure. Contamination can cause certain parts to become dented, including the bearing raceways and balls, which leads to premature and excessive wear and vibration. Contaminants can also inhibit the motor’s ability to regulate its internal temperature, which can lead to overheating, which is another cause of motor failure. Keeping tools and the surrounding workspace clean can help prevent contaminants from getting into the motor.


Vibration can also cause electrical motor failure. Vibration may be due to contamination, but it can also be caused by operating the motor on an uneven surface. If you notice excessive vibration, put the motor on a flat and even surface. If the vibration doesn’t stop, look for loose bearings, wear, or alignment problems. Contact a professional for assistance if you can’t find the source of the problem.


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