Industrial Electric Motor Overheating: Causes and Solutions

Like any complex machine with multiple moving parts, electric motors are vulnerable to common performance problems such as misalignment, bearing wear and harmonic distortion. One of the most common performance problems is overheating of the electric motor.

Experts suggest that an 18°F (10°C) increase in motor winding temperature can directly affect the insulation of the component and reduce its service life by 50 %. This has an irreversible impact on the service life of your machinery, regardless of whether the overheating of the electric motor was temporary or prolonged.

Because heat is the most important enemy that electric motors face, the question is: how can you prevent your electric motor from overheating and minimise the cost of replacing or repairing it?

Protecting your electric motor starts with understanding the most likely causes of overheating.

Common causes of electric motor overheating.

Your electric motor is a complex machine and requires a good balance of environmental factors to run smoothly. Overheating of the electric motor can occur for several reasons:

The most common causes of overheating of industrial engines include:

• An inadequate engine: Motors come in a variety of sizes. Choose an electric motor that can handle the required voltage and performance level needed for your project. A motor that is too large can waste costly energy, and a motor that is too small will not be able to handle an excessive workload, resulting in increased stress and overheating of the machine.
• Incorrect supply voltage: Too much or too little voltage can damage an electric motor. When your motor does not have adequate voltage support, it needs to work harder to operate, which can lead to overheating of the electric motor and its components.
• An unfavourable working environment: An electric motor needs space for air to circulate in order to operate at peak performance. If your machine is operating in a hot environment, it will have difficulty cooling down quickly. Give the machine sufficient space to operate as there is a risk of the electric motor overheating.
• Inappropriate use: Some electric motors can run constantly, while others are intended for intermittent use. Be sure to use your motor only according to its specifications. If you try to run an intermittent duty motor for too long, it will not have the time it needs to cool down between cycles.
• Altitude: The location of the plant can influence the performance of your electric motor. Your machine may not cool as effectively at higher altitudes because the air is less dense. It is important to choose a suitable motor according to where the industrial plant is located, as subjecting it to inappropriate temperatures can cause the electric motor to overheat when you least expect it.
• Lack of ventilation: If something is blocking the vents on your engine, hot air will not escape and will build up in the system, causing damage. Regular maintenance can help reduce the risk of the electric motor overheating.

How to avoid overheating of the electric motor and keep it at a good temperature.

Avoiding problems associated with electric motor overheating requires the right equipment, careful planning and preventive maintenance.

The first step for any maintenance manager, engineer or operations manager before buying an electric motor is to make sure you are buying the right machine for the right type of work. Check that the size, voltage and performance match your specific needs. If you are unsure of your requirements, talk to an expert.

Once you have chosen the right electric motor for your company, find the right place to install it in your industrial space. Remember that where you place it will influence the chances of the electric motor overheating. Keep it away from other heat sources, give it plenty of space and make sure the ventilation openings are clear.

When you start using the electric motor, remember to constantly monitor its temperature and performance for signs of overheating or deterioration. If you have considered all possible problems and your machinery continues to overheat, it could be a sign that something is wrong with the internal components.

You should have a professional perform a thorough check to get a clear answer and minimise the risk of the electric motor overheating in the future.

Main reasons why overheating of the electric motor occurs.

Overheating of the electric motor is one of the main causes of winding and bearing failures. But what causes this excess heat? Understanding the causes of electric motor overheating can help you avoid the problem in the first place or find and fix it more easily once it arises, allowing your equipment to last longer and saving you downtime and additional costs.

Research shows that when the operating temperature is increased by only 10 °C, the service life of the electric motor is halved. Conversely, when the operating temperature decreases by 10 °C, the service life doubles.

Factors related to overheating of your electric motor

Overload

Overloading occurs when the driving force of the equipment meets a resistance in excess of the manufacturer's acceptable rating and may not be a constant problem, as it is directly related to variations in the load of the equipment driven by the motor. Most electric motors operate at maximum efficiency when subjected to only 75% of the manufacturer's rated load. This allows the machine to operate at a lower temperature and consume less energy, thereby reducing the risk of the electric motor overheating.

Ventilation

Electric motors are designed with a system to remove the heat produced during operation. This cooling system may consist of air ducts, air deflectors, cooling fans and other design components such as cooling fins. Many factors can disrupt the ability of the cooling system to perform its function, such as clogged air ducts, build-up of contaminants or ice, operation at a lower than normal speed, etc.

External factors such as ambient temperature, altitude and sunlight can affect the motor's ability to cool itself. Operating in an environment where the ambient temperature is higher than normal for the machine will cause the electric motor to overheat. At higher altitudes, the air is less dense, making it more difficult to dissipate heat, and sunlight can heat up the motor casing. Some users have even painted the housing white and given it additional shade to reduce heat absorption.

Tension

Electric motors operate optimally when the applied voltage is equal to the voltage indicated on the manufacturer's nameplate. Running a motor with a voltage deficit requires higher amperage to produce the required power, and this additional current equals more heat due to resistance. Running the motor at a voltage above the saturation point will also result in additional current and thus excess heat. An unbalanced voltage in a three-phase motor will also cause overheating of the electric motor due to voltage peaks.

Windings

The core of an AC motor is made of many pieces of rolled steel, and the windings are wound through this core. The changing magnetic fields due to the spinning of the rotor can cause a phenomenon called eddy currents inside the steel core. These eddy currents are small and are nothing more than energy losses that generate heat.

Current density

As the wire diameter size of the motor winding wire decreases, the electrical resistance increases. This increase in resistance will result in a loss of energy in the form of heat.

Circulating currents

When the groups of coils in parallel are not equal in number, a circulating current will be produced in the circuit with fewer coils. These circulating currents do not increase the work done by the motor, but are energy losses in the form of heat.

Harmonics

Harmonics are the distortion of the sine wave (total circuit frequency) by waveforms of other frequencies. These disturbances can be caused by the addition of rectifiers, fans and pumps, etc. The odd harmonics produced will create a negative torque which is in opposition to the torque created by the motor. This negative torque increases the load on the motor, causing it to work harder and in turn producing more heat so the risk of overheating of the electric motor is present.

Conclusion

An electric motor operating at high temperature will have a low life expectancy. Reducing the operating temperature by improving ventilation, optimising the design or choosing a machine that is up to the task for which it has been designed will result in more reliable equipment, thus avoiding the risk of overheating of the electric motor.

If you want to know more about the common failures in electric motors contact one of our specialists.

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