The electric motor is heating up: the causes of a malfunction in electric motors for 220 and three-phase for 380 volts – ElektrikExpert.ru

In a situation where a 220 or 380 V electric motor is heating up, it is important to diagnose the problem in time and take measures to eliminate it. If the malfunction is ignored, consequences appear in the form of deterioration in performance and even failure of the unit.

Below we consider the reasons why the rotor and condenser heat up, as well as the electric motor of the pump, fan, trimmer and lawn mower. Let’s talk about why electric motors are on fire, and what to do if a malfunction is detected.

How to understand that the engine is very hot

The temperature of the electric motor is one of the main indicators that requires monitoring during operation. An inversely proportional relationship works here – the lower the operating temperature, the higher the resource.

But it is important to understand that for many electric motors, even +100 degrees Celsius is considered the norm. That is why, before drawing conclusions about the malfunction of the unit, it is necessary to take into account the manufacturer’s recommendations.

Temperatures up to +60 are considered normal.⁰C. If it rises to +70, this is not a problem, but the situation should be taken into account and possibly checked and repaired, or the cooling of the unit should be improved.  

Upon reaching +100⁰C it is important to take the operation of the electric motor under control and identify the causes of overheating. If the temperature parameter continues to rise, it is necessary to disconnect the device from the mains in order to avoid damage to the insulation and an accident.

To determine if the motor is warm or not, you can use one of the following methods:

1. Manual. Quickly touch the motor casing and try to determine its temperature. If after touching you can hold your hand without discomfort, the device has warmed up by no more than +60 ⁰C.
2. Contact thermometer. A device equipped with an external sensor is used for the measurement. Measurements are made in the central part of the casing, where overheating is most noticeable, as well as in front and behind in the area of ​​uXNUMXbuXNUMXbthe bearings.
3. Thermal imager. After turning on the device, you can see all overheating points with an indication of the temperature regime. The downside is that this is expensive equipment that many can not afford.
4. Built-in sensors. In modern models of electric motors for 220 and 380 V, posistors are often structurally provided, allowing you to control the temperature in different places. In the absence of such elements, you can install them yourself and thereby speed up the reaction to overheating of the unit, and, if possible, make it automatic. In the latter case, information from the posistors is transmitted to the frequency converter, and then to the temperature relay or controller input. When choosing the second option, you can set two levels of response. For example, when reaching 70⁰C data is transmitted to the operator, and 100 degrees – the unit turns off.

The method for determining overheating is determined taking into account the type and area of ​​​​responsibility of the electric motor. In domestic conditions, the first option is most often used.

The asynchronous three-phase motor is heated

The causes of overheating of a 3-phase induction motor can be divided into two categories: mechanical and electrical.

The former are associated with the design features of the device, and the latter with the low quality of the supplied voltage.

Mechanical reasons include:

1. An increase in load, for example, due to the addition of additional consumers, a mechanism wedge or foreign elements getting inside.
2. Depreciation of the brushes of the electric motor due to long-term operation.
3. Bearing failure due to lack of lubrication or its poor quality. If nothing is done, the device is destroyed, which leads to damage to the remaining elements of the electric motor.
4. Insufficient cooling, e.g. due to damage to the fan impeller. To solve the problem, additional airflow is required.
5. Distortion of the motor shaft.

Electrical causes have less effect on the temperature of the electric motor, but they should not be dismissed.

The main factors include:

1. Error in the wiring diagram.
2. Breakage / burnout of one of the phases, due to which the mechanical torque decreases, and the engine may stop altogether.
3. Change in input voltage. Asynchronous three-phase motors are sensitive to this parameter. A change of even 5% leads to an increase in heating, and when it reaches 10%, the motor may stop or fail altogether.
4. Internal short circuit between turns or phases. To determine the malfunction, it is necessary to turn off the motor and use a multimeter and an ohmmeter. When closing a small number of turns, the change in resistance is negligible, so it is difficult to identify the problem.

The rotor of the electric motor is heated

Rotor – a rotating element of an electric motor connected to a drive shaft.

Depending on the type of motor, the rotary mechanism may differ in model, brand, manufacturer and characteristics.

Like other elements of the unit, the rotor can heat up, the main reasons are:

1. The power of the rotary mechanism does not meet the requirements established for the operation of the electric motor.
2. Winding fault (break)
3. Insufficient capacitor capacity.
4. Insufficient heat dissipation (poor impeller operation).
5. Breakage or insufficient contact of the squirrel cage rods and short-circuited rings.
6. Stuck shaft. The first signs – the machine knocks out or the fuse blows. When measuring current with a multimeter, the readings are too high. The same applies to the actuator, which is connected to the electric motor through the drive and can also jam. To solve the problem, disconnect the electric motor from the device that drives it and try to manually turn the shaft.
7. Misaligned or damaged bearings (sliding or rolling). If the rotor shaft does not turn manually, then you should make sure that the bearings are in good condition. For plain bearings, a typical problem is the lack of lubrication, which led to their rapid wear. As a rule, carry out the replacement of products.
8. Misalignment and deformation (kink) of the shaft as a result of uneven or increased loads also leads to overheating of the electric motor. As a rule, this problem is typical for powerful units with long shafts.

To prevent the rotor from heating up, it is necessary to maintain an optimal load, observe the temperature regime and operating rules.

The capacitor is heated

There are often complaints on the forums that it is not the engine itself that is heating up, but the capacitors installed in it. The main reason is errors in the choice of capacity without taking into account the negative effect of reactive power.

Most often, MBGO capacitors are installed, for which the variable component should not exceed 20% of the rated voltage.

If it is not possible to select the capacity of the MBGO, taking into account the parameters of the electric motor, it is better to set the MBGCH.

They are designed to work on alternating voltage and are characterized by better cooling.

To solve the problem, many put a resistance in parallel with the capacitor. This is done only to remove the charge after turning off the engine. This design does not carry any other functions. It will not work to reduce overheating in this way.

If the motor capacitor is heated, the best solution is to replace it with a product with a larger capacity or install two capacities – working and starting (connected in parallel).

Switching between devices can be carried out by a button, manually, by current consumption or by time.

The electric motor of the pump, fan is heated

During operation of a pump or fan, a situation often arises with an overheating of the electric motor. Consider the reasons for each of the devices separately.

For fan:

1. Pollution of the impellers, due to which the motor is under increased load.
2. Brush failure.
3. Shaft distortion.
4. Insufficient lubrication/wear of bearings.
5. A problem with the supply voltage, for example, phase imbalance.

This can be seen in the example of a laptop cooling fan (cooler).

For the pump:

1. Excessive load not specified by the manufacturer.
2. Overload at start.
3. Cooling system failure.
4. Change in mains voltage.
5. Accumulation of dirt inside.
6. Strong rotor vibrations.

The reasons why the pump and fan motors heat up are usually identical. They are associated with a load mismatch or mechanical failure of the equipment.

Idling

There is an opinion that an electric motor without load should not warm up, but this is not so. For capacitor motors, temperature rise in this mode is a common occurrence. Moreover, prolonged operation at idle can lead to overheating and equipment failure.

Otherwise, the causes of high temperatures are the same as in the cases discussed above: inter-turn short circuit, accumulation of dirt, damage to bearings, etc.

Trimmer engine running hot

An electric trimmer is one type of lawn mower that has a simpler design. In such devices, gasoline or electric motors are installed.

When choosing the second option, it is necessary to take into account the power of the unit, because the ability of the device to cope with the task depends on it.

There are several reasons why the electric motor can heat up and even smoke:

• long work (over the recommended parameter);
• increased load arising from the ingress of foreign objects and blocking of the knives;
• wrong choice of brushes or their incorrect location;
• winding damage;
• small cross-section of the wire in the extension cord;
• the use of too thick fishing line;
• grass getting stuck between the reel and line.

In order to avoid problems with the electric motor, it is important to read the instructions before use and follow the manufacturer’s recommendations.

Lawn mower motor overheating

Many lawn mowers have an electric motor that can overheat and shut down in certain situations.

The reasons may be as follows:

• turn-to-turn circuit in the winding;
• problems with the starting capacitor (capacitance mismatch, failure);
• long work (over the recommended parameter);
• distortion of the flanges during assembly, which creates an increased load on the bearings;
• incorrect connection (for example, mixed up main and starting windings);
• wear and damage of brushes/bearings;
• supply voltage problems.

Judging by the reviews on the Web, common causes of overheating of a lawnmower electric motor are an interturn circuit and working with the device beyond the set time.

A 3-phase motor connected to 220 V is heated

Many craftsmen connect a three-phase motor using 220 V capacitors. Subsequently, they complain that the unit is heating up for some reason.

There may be several explanations for this:

1. Interturn circuit of the windings.
2. Wrong choice of capacitor (capacity, type).
3. Error in the wiring diagram.
4. Lack of sufficient cooling (relevant for high power engines).
5. Prolonged idling.

Other problems are the same as in other types of electric motors.

Why do electric motors burn?

One of the common questions on the Internet is why electric motors burn.

Experienced electricians identify several reasons:

1. Long-term overload and operation in a mode not provided by the manufacturer (inconsistency in humidity, temperature).
2. Violation of the integrity of the unit.
3. Errors in storage, installation and transportation.
4. Switching to low or, conversely, high voltage.
5. Unbalance of the drive or parts on the motor shaft.
6. Improper operation, pollution of ventilation units.
7. Connection errors. For example, choosing the wrong scheme (a triangle instead of a star).
8. Voltage imbalance or phase failure.
9. Lightning discharge and high voltage in the network.
10. Long-term heating of the winding.
11. Ingress of water or foreign objects into the electric motor.

What to do if overheating is suspected

In conclusion, consider what to do if the electric motor is heating up.

The general algorithm is as follows:

1. Determine the overheating temperature and de-energize the motor when the critical parameter is reached.
2. Evaluate the presence of extraneous noise during operation. If the sound is coming from inside the engine, the problem is most likely with the bearings. They need to be checked, lubricated or replaced.
3. Check the current by phase to conclude if it is skewed or overloaded.
4. Release the load and let the machine idle.
5. Make sure the air cooling is working properly.
6. Check the operation of the current protection.

To protect against overheating, it is recommended to control the current and voltage, as well as install automata and thermal relays at the input.

If you find that the electric motor of the trimmer, pump, fan, lawn mower or other equipment is heating up, take immediate action. Timely diagnostics allows you to identify the problem, eliminate the malfunction and avoid the final expensive unit.

What do you think about it? What is the cause of your motor overheating? Write in the comments.