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The 5 most common reasons for electric motor failure

Here at Gibbons we’ve been offering electric motor rewinds for 45 years, so there isn’t much we haven’t seen when it comes to motor failure. Today we’re looking at the five most common reasons electric motors fail.

Inadequate lubrication

Electric motor lubrication is quite a delicate balancing act, because excessive or insufficient greasing can both lead to bearing failure. Too little grease means excessive friction between rotating parts and bearings occurs, while over-lubricating causes the grease to be churned, resulting in overheating.

There are greases which are specifically designed for electric motors and others that are for general use, so it’s important to select the correct type. Another lubrication issue is contamination, as foreign matter can increase bearing wear which will lead to premature failure.

Excessive heat

When an electric motor overheats, the increased temperature causes the winding insulation to melt. Once the windings are unprotected, a short circuit occurs and results in failure. Each time a motor’s windings exceed 10°C above the intended operating temperature, the insulation life drops by as much as 50%.

It’s crucial that an electric motor is housed in a well-ventilated area away from a heat source, with temperatures carefully monitored.


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

To guard against dust contamination, users can select a motor with an appropriate Ingress Protection (IP) rating, a system which 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 causes electric motor winding insulation to deteriorate and metal parts to corrode. When a motor is running continuously, the heat created helps drive out moisture, but when a motor operates intermittently, 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.

Power supply problems

Voltage and current distortion occurs as a result of harmonic currents caused by high-frequency switching and pulse-width modulation. This leads to overloading and overheating, reducing the motor’s service life. Power surges, along with over and under-voltage, can also be damaging so it’s important to monitor the power supply and ensure it’s adequate for the motor being run.

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

Electric Motors

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