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Why do electric motors fail?

Here at Gibbons we’ve been providing electric motor rewinds for 46 years, so we’ve seen it all when it comes to motor failure. Here we’ll examine five of the most common reasons for electric motors failure.


When an electric motor overheats, the temperature rise causes the winding insulation to melt which leaves the windings unprotected. A short circuit then occurs, resulting in motor failure. Each time a motor’s windings exceed 10°C above the intended operating temperature, the insulation life drops by as much as 50%.

Therefore, you should ensure that electric motors are housed in a well-ventilated area away from heat sources, with temperature carefully monitored.

Lubrication problems

Electric motor lubrication should be performed with caution, as excessive or insufficient greasing can both lead to bearing failure. A lack of grease leads to excessive friction between rotating parts and bearings, while over-lubricating causes the grease to be churned, pushing it out of the way and resulting in energy loss and temperature rise.

Some greases are specifically designed for electric motors and should be used instead of those intended for general use.

Also be wary of lubricant contamination, as foreign matter can accelerate bearing wear and lead to premature failure.

Power supply issues

Harmonic currents caused by high-frequency switching and pulse-width modulation result in voltage and current distortion. This leads to overloading and overheating which diminishes the motor’s service life. Power surges, along with over and under-voltage, can also be detrimental so the power supply should be monitored to ensure it’s suitable for the motor being run.


Airborne dust particles can be fine enough to enter an electric motor, and once inside they will wear down components over time. Some fragments will block cooling passages and cause overheating, while other particles are electrically conductive and can interfere with currents.

To avoid dust contamination, users can select a motor with an applicable Ingress Protection (IP) rating. (The IP system classifies the motor enclosure’s defence against objects, dust and moisture.) This rating ranges from no special protection to hermetically-sealed enclosures that guard fully against dust.


Exposure to moisture results in the deterioration of electric motor winding insulation and corrosion of metal parts. Continuous running of a motor creates heat which helps drive out moisture, but intermittent operation means the moisture has time to accumulate and cause damage. In this case, motors should be kept warm enough during shutdown periods to prevent condensation from forming.

If you have an electric motor you’d like us to rewind or repair, Gibbons provide a free collection and delivery service within a 50-mile radius and offer an emergency next-day service wherever possible. Plus, there’s a 12-month warranty on repairs and we can attend site if required. So for a competitive motor rewinding quote, call Matthew on 07970676272 or email

Electric Motors

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