The article shows the malfunctions of electric motors that appear during their operation and lead to the failure of electric motors.
Introduction
When electricity flows through the 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 a current not exceeding 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 increases for some reason, then the electric motor will start to overheat, and if this process is not stopped, then in the future the electric motor will fail. In the windings, due to overheating, the insulation of the conductors begins to melt (usually a special varnish) and a short circuit of the conductors occurs.
Below we consider possible ways increasing current through the motor windings.
Operating methods leading to malfunction of electric motors
Method 1. Motor overload.
This is the most common way. In the absence of protection, overload the electric motor: stop or significantly slow down 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 - apply to the pump inlet to the pumped liquid foreign body eg (fibrous materials, dross after welding of heating pipes).
Important notice for submersible pump and fan motors!
Deep-well pumps, fans, under some operating conditions, it is enough to turn on with an open output (and for a fan - with an open input) to overload the engine. According to the instructions, the pump or fan should be started with a closed valve (valve) at the pump outlet or a closed damper at the fan inlet. After the unit is started, the valve or gate opens simultaneously with the measurement of the current consumption of the electric motor. Gradually, by opening the valve or gate, the current value is brought to the nominal value and at the same time the valve or gate is fixed. Further opening of the valve or gate puts the electric motor into overload mode. But who makes 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 drainage pump - 20 minutes, the fan - how lucky: if there is air resistance at the fan outlet (narrow air ducts, for example, or a bunch of grain during drying) - it can work for a long time, but if the resistance air drops - the engine quickly goes into overload and fails.
Method 2. No phase or phase imbalance.
Start the electric motor in two phases or, when the electric motor is running, tear off (break off) or disconnect the wire with one phase. In two phases, the electric motor can work - but not for long, because. at the same time, an increased current flows through the windings to which voltage is applied (the current through the winding increases up to 50%).
Method 3: Connection errors.
Connect the motor windings incorrectly. Typically, the motor tag indicates how the voltage windings are connected. For example, Δ / Υ 220/380 - a "triangle" for 220V, a "star" for 380V. If for such an electric motor we connect the windings in a “triangle” and turn them on at 380V, then the engine will work, but not for long. A current 1.7 times greater than for the same load according to the "star" scheme will flow through the windings, and after a while the electric motor will overheat and burn out.
Method 4. Installation errors.
When mounted on the shaft of the coupling half or pulley no need to provide a stop for the shaft on the opposite side(Often, after all, in this case, it is necessary to remove the protective casing of the fan from the engine - but whoever does this will suddenly come down anyway). Also, during installation, it is necessary to apply powerful blows when fitting a pulley or coupling half. The combination of these actions is almost guaranteed to result in damage to the bearings or the back cover of the 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.
Important addition! The main condition for a reliable failure of the electric motor is the lack of protection of the electric motor or the discrepancy between the protection devices and the electrical parameters of the electric motor. The electric motor is protected either by a specialized device for protecting electric motors.
It should be noted that motor protection is an extra cost (10-40% of the motor cost). Therefore, if you intend to update your electric motors as often as possible, then save money on protection.
Method 5. Unacceptable operating conditions.
Sergey Soyuk, who rewinds electric motors, from his experience pointed out 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 electric motor against dust and water. Most often it is IP54 or IP55. The first digit is protection against solid objects. The second digit is protection against liquids: 4 - against water splashes from all sides; 5 - from water jets. However, if you pour water on the electric motor from a hose or leave it in the rain, then water can get inside the electric motor (through the wires through the terminal box, for example) and this will lead to the failure of the electric motor.
5.2. Unbalance of the drive or part attached to the motor shaft.
For example, imbalance of the fan impeller leads to transverse beats of the motor shaft, which will eventually lead to the destruction of the bearing and end shield. Therefore, the fan does not need to be cleaned, let dirt stick to the impeller - and after a while the motor itself will fail. By the way, for "pumping" air from great content dust (up to 1 kg per cubic meter) there are special dust fans with radial blades.
From myself I will add one more way.
5.3. Overheating of the electric motor when adjusting its speed.
When the speed of the electric motor is reduced with the help of a frequency converter, the air flow for cooling the electric motor from the impeller located at the other end of the shaft is reduced. Remember that when the impeller speed is reduced by 2 times, the fan performance decreases by 2 times, and the pressure by 4 times. Therefore, the motor cools worse when the 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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Electric motor malfunctions - find out why the electric motor fails? Alexander Koval 
62 comments
We all know that mechanical movement in electrical devices for various purposes, it is provided by an electric motor. But at long work in the mode of increased loads, they begin to heat 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 the water supply system, pumps are also used, the driving force in which there are electric motors. During operation, when replacing and installing the motor, it is important to know why it is heating 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?
You need to treat the problem of engine heating with special attention, because the insulation of its winding has a weak resistance to elevated temperatures. Often the temperature is in the range of 90-95 ºС. There are electric motors winding, which is designed for a maximum temperature of 130 ºС.
But in any case, during operation, emergency overloads or technological malfunctions can 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 performance of the device, an expensive repair of the engine or its complete replacement. It will be less costly to find out the cause of the heating of the electric motor and eliminate it than to buy new engine or order its rewind.
Often the cause of an engine overheating is:
- failure of power lines;
- increased workloads;
- wear of the brushes of the electric motor;
- shaft skew;
- poor lubrication and increased wear bearings;
- failure or inefficient operation of the engine cooling device (fan).
You can find out the cause of the motor heating if you turn it on without load. But first you need to study the passport of this device, which reflects information about the maximum load.
In the event that it is greater than the actual one, you must first reduce the amount of work performed by the unit.
The incorrect operation of the technological installation is evidenced by the ideal operation of the engine without load. But if it heats up without load, then the reasons lie inside this unit.
Many of them will not be difficult to eliminate, for example, if the cause of the temperature increase is an idle cooling fan. It may be poorly lubricated or clogged with dust, and in order to restore normal mode its operation requires only lubrication or dust removal of the fan.
Regardless of what caused the increase in temperature of the electric motor, this malfunction must be corrected and as soon as possible. Since further operation of the engine may lead to more serious problems, its service life will decrease several times.
Most often the problem elevated temperature electric motor is solved by lubricating the bearing, stabilizing the voltage in the mains, which feeds one or another power unit, removing dirt and dust from winding surfaces. 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. At the same time, it will function normally at a voltage that is less than the nominal voltage by no more than 20%. Eliminate more complex reasons 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 first of all to clean it, make sure that the bearing caps are tightly closed. If the bearing has opened as a result of strong vibration It's likely that dirt and dust got into it. The part is cleaned by washing it with kerosene, after which it is necessary to blow it with compressed air.
At the end of the restoration of normal operation of the bearing, it is filled clean lubricant, the characteristics of which correspond to the speed of the electric motor. You need to add it in small portions using special devices. At the same time, it is important not to overdo it with the amount of lubricant, otherwise the sliding will be difficult, and the motor will still be under load.
In addition, the cause of the motor heating may be a problem with the supply voltage. This can be either increased or decreased voltage, loss or. Under such a situation, the motor operates under abnormal conditions, which entails a change in its electrical characteristics, increase in current in the windings. Therefore, it is necessary to take a tester and check the voltage in the network, the presence of phases, the uniformity of the 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 was 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 motor shaft has increased.
Maybe there is a rubbing of bearings inside the electric motor. Or maybe the engine is without lubrication and runs dry. Check if the wires in the winding are shorted. Perhaps a phase imbalance has occurred or the voltage is not correct.
Whether the engine power is allowed to work 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 quickly eliminate it, 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.
Overheating of the electric motor is one of the most common malfunctions, the consequence of which may be the failure of the unit. Why is it heated asynchronous electric motor And what needs to be done to prevent this from happening?
Causes of engine overheating
Heating can be caused by a variety of factors. Most often this is due to:
- Operation in an unacceptable mode. The device must not for a long time work under increased stress and be subjected to mechanical influences(shocks, sharp shocks, vibration) - this violates the integrity.
- Corrosion caused by sudden and frequent changes in temperature 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. You should strictly follow the instructions given in your passport.
- Winding insulation damage. It can occur when foreign particles get under the body or during careless transportation. The consequences are different - local short circuits, shaft deformation, uneven rotation of the rotor, and as a result - overheating.
- Operation with increased or reduced voltage in the network. Trying to find the answer to the question: why is the 3-phase electric motor 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 destruction. Signs of this malfunction are immobility or poor rotation of the rotor when the device is turned on, complete jamming of the rotor and stator, and heating of the housing.
In most cases, heating of the motor winding can be prevented simply by strictly observing the operating rules. Sometimes it is enough to turn it off and leave it at rest 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 bring the unit to breakage. To do this, take measures to protect the motor from overheating:
- Do not overload the device.
- When the engine is not in use, store it in a room with acceptable temperature and humidity.
- Periodically check the condition of the nodes.
If the mechanism and the housing are often and strongly heated, the causes of this should be identified and eliminated:
- Replace bearing.
- Rewind 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 how to eliminate them is necessary in order, firstly, to prevent overheating itself, and secondly, to be able to independently identify the problem and fix it, if it is in your power.
