Overheating of the electric motor is one of the most common malfunctions, the consequence of which can be the failure of the unit. Why is it heated asynchronous motor and what needs to be done to prevent this from happening?
Causes of engine overheating
Heating can be triggered by a variety of factors. Most often, this is due to:
- Operation in an unacceptable mode. The device should not operate under increased load for a long time, or be exposed to mechanical stress (impacts, sharp shocks, vibration) - this violates the integrity.
- Corrosion caused by sudden and frequent temperature changes and high humidity... Reducing the gap between the elements due to rust leads to the fact that the electric motor does not pick up speed and heats up.
- Failure to comply with the rules of storage, installation and transportation. The instructions given in the passport should be strictly followed.
- Damage to the winding insulation. It can occur if foreign particles get under the housing or during careless transportation. The consequences are different - local short circuits, shaft deformation, uneven rotor rotation, and, as a result, overheating.
- Operation with overvoltage or undervoltage in the network. Trying to find the answer to the question: why the 3-phase electric motor is heating up, check the wiring and the condition of the sockets.
- Clogged ventilation ducts. To avoid this, it is enough to regularly inspect and clean the engine.
- Constant too high / low temperature in the room where the engine is running.
- Bearing failure. Symptoms of this malfunction are immobility or poor spinning of the rotor when the device is turned on, complete jamming of the rotor and stator, and heating of the housing.
In most cases, it is possible to prevent heating of the electric motor winding simply by strictly observing the rules of operation. Sometimes it is enough to turn it off and leave it dormant for a while. If the elements are already damaged, they need to be repaired or replaced.
Preventive measures necessary to protect the motor from overheating
Of course, it is better not to let the unit break down. For this, measures should be taken to protect the electric motor from overheating:
- Do not overload the device.
- If the engine is not yet in use, store it in a room with an acceptable temperature and humidity.
- Check the condition of the components periodically.
If the mechanism and the case are often and very hot, you should identify the reasons for this and eliminate them:
- Replace bearing.
- Rewind the windings.
- Remove rust from parts.
- Change winding insulation.
- Clean ventilation ducts.
In "neglected" cases, you will have to take the unit to a repair shop.
Knowing the causes of engine overheating and ways to eliminate them is necessary in order, firstly, to prevent overheating itself, and secondly, to be able to independently determine the problem and fix it, if it is in your power.
The article contains malfunctions of electric motors that appear during their operation and lead to the failure of electric motors
Introduction
When an electric current flows through a conductor, the conductor heats up. Therefore, the electric motor heats up during operation. The design of the electric motor is calculated in such a way that if no more than the rated current flows through the windings, then such an electric motor will operate at a temperature environment according to the climatic version of the electric motor and. The rated current is indicated on
But if the current through the motor windings for some reason increases, then the electric motor will start to overheat, and if this process is not stopped, then the electric motor will fail in the future. In the windings, due to overheating, the insulation of the conductors begins to melt (usually this is a special varnish) and a short circuit of the conductors will occur.
Consider below possible ways increasing the current through the motor windings.
Operating methods leading to malfunction of electric motors
Method 1. Overloading the electric motor.
This is the most common way. In the absence of protection, overload the electric motor: stop or significantly brake the rotating shaft of the electric motor. How? Depending on the mechanism. For a sawmill, for example, quickly put a thick log with branches on the saw, for a cantilever pump - supply a foreign body to the pump inlet into the pumped liquid, for example (fibrous materials, scale after welding heating pipes).
Important note for submersible pump and fan motors!
Submersible pumps, fans under some operating conditions, it is enough to turn on with an open outlet (and for a fan - with an open inlet) to overload the motor. According to the instructions, the pump or fan must be started with a closed valve (valve) at the pump outlet or a closed gate at the fan inlet. After starting the unit, the gate valve or gate opens simultaneously with the measurement of the current consumption of the electric motor. Gradually, by opening the gate valve or gate, the current value is brought to the nominal value, and the gate valve or gate is fixed. Further opening of the valve or gate brings the electric motor into overload mode. But who does it so difficult - it is better to immediately throw the valve or gate out of the circuit (which will save money) and turn on the unit directly. The result will not keep you waiting long - the deep pump can work for a month, the drain pump - about 20 minutes, the fan - how lucky: if there is air resistance at the fan outlet (narrow air ducts, for example, or a pile of grain when drying) - it can work for a long time, but if the resistance air falls - the engine quickly goes into overload and fails.
Method 2. Lack of phase or phase imbalance.
Start the electric motor on two phases or, when the electric motor is running, tear off (break off) or disconnect the wire with one phase. The electric motor can work on two phases - but not for long, because in this case, an increased current flows through the windings to which the voltage is applied (the current through the winding increases to 50%).
Method 3. Connection errors.
Wrong connection of motor windings. Typically, the motor tag indicates how the voltage windings are connected. For example Δ / Υ 220/380 - "triangle" for 220V, "star" 380V. If for such an electric motor you connect the windings with a "triangle" and turn them on at 380V, then the motor will work, but not for long. The current will flow through the windings 1.7 times more than for the same load according to the "star" circuit, and after a while the electric motor will overheat and burn out.
Method 4. Installation errors.
When attaching a half-coupling or pulley to the shaft it is not necessary to provide support for the shaft on the opposite side (Often, in this case, it is necessary to remove the protective fan casing from the engine - but whoever does this will suddenly come off). Also during installation it is necessary to apply powerful blows when attaching a pulley or half-coupling. A combination of these actions is almost guaranteed to damage the bearings or the back cover of the electric motor (especially if the cover is cast iron). A cracked cover or damaged bearing will not withstand the loads during engine operation and will cause engine failure.
An important addition! The main condition for a reliable failure of the electric motor is the lack of protection of the electric motor or the inconsistency of the protection devices with the electrical parameters of the electric motor. The electric motor is protected by either or specialized devices for protecting electric motors.
It should be noted that the protection of an electric motor is an extra cost (10-40% of the cost of the motor). Therefore, if you intend to update your electric motors as often as possible, then save money on protection.
Method 5. Inadmissible operating conditions.
Sergei Soyuk, who rewinds electric motors, from his experience indicated two more reasons for the failure of electric motors during their operation: water ingress into the electric motor and imbalance of the drive or part attached to the motor shaft.
5.1. Water ingress into the motor.
The electric motor tag indicates the dust and water proof motor. Most often it is IP54 or IP55. The first number is protection against solid objects. The second number is protection against liquids: 4 - against water splashes from all sides; 5 - from water jets. However, if you water the electric motor with water from a hose or leave it out in the rain, then water can get inside the electric motor (through wires through the terminal box, for example) and this will lead to failure of the electric motor.
5.2. Unbalanced drive or part attached to the motor shaft.
For example, imbalance of the fan impeller leads to lateral beating of the motor shaft, which will ultimately lead to the destruction of the bearing and end shield. Therefore, the fan does not need to be cleaned, let dirt adhere to the impeller - and after a while the motor itself will fail. By the way, for "pumping" air with a high dust content (up to 1 kg per cubic meter) there are special dust fans with radial blades.
On my own I will add one more way.
5.3. Overheating of the electric motor when regulating its speed.
When the speed of the electric motor decreases with the help of the frequency converter, the air flow for cooling the electric motor from the impeller located at the other end of the shaft decreases. Remember that when the impeller speed decreases by 2 times, the fan performance decreases by 2 times, and the pressure - by 4. Therefore, the motor cools worse when the rotational speed decreases and, therefore, overheats faster.
If you know more ways to disable electric motors - write to us and the whole world will know about your experience.
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Motor faults - find out why an electric motor fails? Alexander Koval 
62 comments
We all know that mechanical movement in electrical devices for various purposes is provided by an electric motor. But with long work in the mode of increased loads, they begin to warm up, which can lead to overheating and damage to the device. Therefore, before using it, you must read the instructions very carefully.
Often it is necessary to repair electrical appliances and replace the electric motor in them. Some craftsmen create their own electromechanical devices, which include an electric motor. When installing a water supply system, pumps are also used with a driving force, in which there are electric motors. During operation, when replacing and installing a motor, it is important to know why it heats up, how to choose such a device in order to increase the period of use of the electrical appliance as a whole and reduce the risk of its breakdown.
So, why does the electric motor heat up and how to prevent it from overheating?
Special attention should be paid to the problem of heating the motor, because the insulation of its winding has a weak resistance to high temperatures. Temperature is often the norm, in the range of 90-95 ºС. There are electric motors, the windings in which are designed for a maximum temperature of 130 ºС.
But in any case, during operation, emergency overloads or technological malfunctions may occur, which lead to heating, which is the cause of insulation failure. After that, a short circuit often occurs. As a result, to restore the operability of the device, expensive repair of the engine or its complete replacement... It will be less costly to find out the reason for the heating of the electric motor and eliminate it than to buy new engine or order it to rewind.
Engine overheating is often caused by:
- failure of power lines;
- increased workloads;
- wear of the brushes of the electric motor;
- shaft misalignment;
- poor lubrication and increased bearing wear;
- failure or ineffective operation of the cooling device (fan) engine.
You can find out the reason for the heating of the motor if you turn it on without load. But first it is necessary to study the passport of this device, which reflects information on the maximum load.
In the event that it is more than the actual one, you must first reduce the amount of work performed by the unit.
Incorrect technological installation is evidenced by perfect job engine without load. But if it heats up without load, then the reasons lie inside this unit.
Many of them can be easily eliminated, for example, if the reason for the temperature rise is an inoperative cooling fan. It may be poorly lubricated or clogged with dust, and all that is needed to restore normal operation is to lubricate or dust the fan.
Regardless of what caused the increase in the temperature of the electric motor, this malfunction must be eliminated and as soon as possible. Since further operation of the engine can lead to more serious problems, its service life will be reduced several times.
Most often, the problem of an increased temperature of an electric motor is solved by lubricating the bearing, stabilizing the voltage in the electrical network that supplies one or another power unit, removal of dirt and dust from the surfaces of the winding. In the event that it is not possible to equalize the voltage in the network, it is necessary to reduce the load on the motor. In this case, it will function normally at a voltage that is less than the nominal voltage by no more than 20%. Elimination of more complex causes of heating is carried out by cleaning or replacing brushes, rewinding the motor. 
If the temperature rise of the motor is affected by the heating of the bearing, then it is necessary to first clean it, make sure that the bearing caps are tightly closed. If the bearing has opened as a result of strong vibration, it is likely that dirt and dust has got into it. The part is cleaned by flushing it with kerosene, after which it is necessary to purge compressed air.
At the end of the restoration of normal operation of the bearing, it is filled clean grease, the characteristics of which correspond to the speed of the electric motor. You need to add it in small portions using special tools. In this case, it is important not to overdo it with the amount of lubricant, otherwise sliding will be difficult, and the motor will continue to experience a load.
In addition, a problem with the supply voltage can cause the motor to heat up. It can be either overvoltage or undervoltage, loss or. In such a situation, the motor operates under abnormal conditions, which entails a change in its electrical characteristics, an increase in the current in the windings. Therefore, you need to take a tester and check the voltage in the network, the presence of phases, the uniformity of the current voltage on each of them. There may be certain discrepancies, but if their value is large, then you need to look for and eliminate the cause.
In any case, if it was noticed that the temperature of the electric motor is increased, and it should be less than 125 degrees Celsius, then it is necessary to find out the reasons. You need to see if the mechanical load on the engine shaft has increased.
Maybe the bearings are rubbing inside the electric motor. Or maybe the engine is without lubrication and runs dry. Check if the wires in the winding are shorted. Perhaps there is a phase imbalance or the voltage is abnormal.
Whether the engine powers are allowed to run in this device. In any case, if the motor overheats, then one of the above reasons must be present. At the same time, it is important to install it in a timely manner and eliminate it as quickly as possible, without exposing the engine to increased loads for a long period of time.
Write comments, additions to the article, maybe I missed something. Take a look at, I will be glad if you find something else useful on mine.
During operation, the electric motor may start to warm up. This problem should be treated with increased attention, since the insulation of the winding does not tolerate high temperatures. In most cases, it is designed for normal daily work in the range of 90-95 ° C. Some motors are built using windings for which the temperature is critical at 130 ° C. If during operation there are emergency overloads or technological malfunctions, the engine will start to warm up, and the winding insulation will fail as a result. The next stage in the development of the situation will probably be a short circuit, which will lead to the need expensive repairs... To prevent this from happening, it is necessary to find out why it is heating up and eliminate the reasons. In most cases it is less expensive than rewinding or buying new motor... The main causes of engine overheating The reasons why an engine can overheat can lie on a variety of planes. The main ones include:
- supply line faults electric current;
- wear of the motor brushes;
- shaft misalignment;
- bearing wear or poor lubrication;
- malfunction of the fan cooling the engine.
To find out why the electric motor is heating up, you can turn it on without load. But before that, it is worth examining the motor passport, which indicates the maximum load. If it does not correspond to the actual one, then it is worth trying to reduce the amount of work performed by the power unit. When the unloaded motor is running perfectly, it is only the wrong technological processes... In the event that the motor heats up without load, then the reasons are probably inside the power unit. Some of them can be easily eliminated, for example, if it is all about the fan cooling the rotor. It can become clogged with dust and it is enough to clean it to temperature regime work became normal again. The main ways to eliminate engine heating Having found out the cause of the engine heating, you should definitely eliminate the malfunction. Otherwise, the service life of the engine can be reduced several times. The most commonly used methods for eliminating heating of electric motors are bearing lubrication, voltage stabilization in the network supplying the power unit, removal of dust and dirt from the winding surface. If the voltage cannot be equalized, then the load on the motor should be reduced. Normal operation of the motor is possible only if the voltage is at least 80% of the nominal. More complex reasons motor heating is eliminated in specialized workshops, where brushes are cleaned or replaced, and a new motor winding is made. What to do if the electric motor bearing gets warm? For normal work care must be taken to keep it clean. Make sure that the bearing caps are tightly closed. If they were opened due to strong vibration, then they are likely to have gotten dust, dirt or debris. For further operation of the bearing, it is necessary to remove the contaminated grease, thoroughly rinse the part with kerosene, and blow it with compressed air. After that, it is necessary to fill the bearing with grease - the one that corresponds to the engine speed. It is added in small portions with the help of special devices. It is impossible to overdo it with the amount of lubricant, since sliding in this case will be difficult and the electric motor will again experience an increased load.
