Permanent the hum coming from the kitchen is a normal phenomenon for working equipment, but few people think about what exactly is happening inside the metal box at this moment. The heart of any cooling system is compressorwhich is often mistakenly called simply a motor, although technically it is a combination of an electric motor and a pump part. It is this unit that forces the refrigerant to circulate through the tubes, taking heat from the chambers and releasing it into the environment through the condenser.
Understanding the principle of operation motor-compressor is necessary not only for engineers, but also for ordinary users who want to extend the life of household appliances. Knowing how the engine starts and why it may shut down prematurely can help you avoid costly repairs or complete replacement. In this article we will analyze in detail the internal structure, stages of the cooling cycle and typical scenarios for the failure of this critical element.
Design and structure of the compressor
Externally motor-compressor is a sealed black or gray metal cylinder (tank), inside which the unit itself is suspended on springs. Such a suspension is necessary to dampen vibrations that occur during operation of the piston group. Inside the tank there is electric motor a compressor part, operating in a single environment saturated with oil and freon vapors. The tightness of the housing is a key requirement, since moisture or air entering the system will lead to blockage of the capillaries and the formation of acids that destroy the windings.
The electrical part consists of a stator with windings and a rotor that rotates inside it. A crank mechanics is attached to the rotor shaft, converting rotational motion into translational motion of the piston. Unlike car engines, there are no timing valves in the traditional sense - thin reed valves made of special steel are used, which open and close under the influence of pressure. They ensure unidirectional gas movement.
To start the engine, a starting relay is used, which briefly supplies current to the starting winding, creating the necessary torque. After the rotor picks up speed, the starting winding is turned off, and the motor continues to operate on the working winding. Thermal relay protects the unit from overheating by opening the circuit when the body temperature rises critically or when there is a current overload.
⚠️ Attention: It is strictly forbidden to open the sealed compressor casing at home. There may be gas under pressure inside, and a violation of the seal will lead to irreversible damage to the unit and the need for its complete replacement.
Modern models are often equipped with inverter engines, the design of which is significantly different from the classic ones. They are not strictly tied to the rotation speed, which allows you to smoothly regulate the power.
What is the difference between an inverter motor and a conventional one?
The inverter compressor does not turn off completely after reaching the desired temperature, but only reduces the speed to a minimum, maintaining the cold. This reduces wear on mechanical parts and noise levels, but makes the electronics more sensitive to power surges.
Operation principle: cooling cycle
The operation of a refrigerator is based on the physical property of substances to absorb heat during evaporation and release it during condensation. Motor-compressor in this process it acts as a pump that “pushes” refrigerant in a closed circuit. The cycle begins with low pressure and temperature freon gas entering the compressor. The motor compresses this gas, sharply increasing its pressure and temperature.
Next, the hot gas under high pressure enters the condenser (the grill on the back wall of the refrigerator). Here it cools down and turns into a liquid state, giving off heat to the air in the kitchen. After the condenser, the liquid refrigerant passes through the filter drier and enters the capillary tube. This is a very thin channel that serves as a choke: it sharply reduces the freon pressure before it enters the evaporator.
In the evaporator, located inside the chambers or behind the back wall, the refrigerant boils at a very low temperature, actively absorbing heat from the interior of the refrigerator. Having turned back into gas, it returns to the compressor, and the cycle repeats. Thermoregulator or an electronic module controls the temperature inside the chambers and gives a command to stop or change the power of the motor.
- 🔄 Compression: The motor compresses the gaseous refrigerant, increasing its energy.
- 🔥 Condensation: The gas cools in the condenser coil, turning into liquid.
- ❄️ Evaporation: The liquid expands sharply in the evaporator, taking heat from the chambers.
- 💨 Return: The cooling gas returns to the motor to repeat the cycle.
It is important to understand that the motor does not operate constantly, but in cycles. The duration of work and rest depends on the load of the chambers, the ambient temperature and the tightness of the door seals.
Types of compressors: piston and inverter
Two main types of engines dominate the household appliances market, each of which has its own design and operation features. The classic piston compressor works on the principle of reciprocating motion. It either turns on at full power or turns off. This is a time-tested technology, characterized by maintainability and the cost of the unit itself.
Inverter models that have become widespread in recent years use an engine with variable shaft speed. The electronic control unit (inverter) converts alternating current into direct current, and then again into alternating current, but at the desired frequency. This allows the motor to operate continuously, varying performance from 10% to 100%. The absence of constant inrush currents and sudden starts significantly reduces the load on mechanical parts.
Comparing the characteristics helps you understand which type is (more suitable) for your operating conditions. Piston motors are noisier and consume more energy at startup, but they are less sensitive to the quality of the network voltage. Inverters are quieter and more economical, but their repair often requires replacing the entire expensive control module.
| Characteristics | Piston (Normal) | Inverter |
|---|---|---|
| Operating principle | On/Off (cyclically) | Smooth speed control |
| Noise level | High (especially at start) | Low, uniform hum |
| Energy consumption | Medium/High | Low (class A++ and higher) |
| Service resource | About 10 years | Up to 20 years or more |
| Sensitivity | Low | High (stabilizer required) |
The choice between them is often dictated by the budget: the initial cost of refrigerators with inverter motor higher, but in the long run they benefit from saving electricity.
Starting and thermal relay: protection motor
For normal startup and operation electric motor not only the compressor itself, but also the attachments are responsible. A starting relay is an electromagnetic or posistor device that supplies a pulse to the starting winding only at the moment of start. As soon as the rotor reaches about 75% of the rated speed, the relay opens the starting winding circuit. If this does not happen, the winding will burn out from overload.
Thermal relay (often combined with a starting relay in one "pill") acts as a fuse. Inside it is a bimetallic plate that bends when heated. If currentconsumed by the motor exceeds the norm (for example, due to jamming of the piston or voltage drop), the plate heats up and opens the contacts, turning off the power. This saves the windings from burning.
A frequent problem is sticking of the starting relay contacts or loss of properties by the posistor. In this case, the engine may hum, trying to start, but will not start until the thermal protection is activated. Replacing these elements is inexpensive and is often carried out by craftsmen at home.
- 🔌 POSISTOR: a semiconductor element that changes resistance when heated is used in modern relays.
- ⚡ Electromagnetic relay: a classic version, where the coil draws in the core to open the contacts.
- 🌡️ Bimetallic plate: the main element of thermal protection that responds to temperature.
Relay diagnostics often begin with a visual inspection for carbon deposits and contact testing with a tester.
Diagnostics of motor malfunctions
Understanding how it works refrigerator motorallows you to quickly identify anomalies in its behavior. The first and most obvious sign of trouble is the nature of the sound. A working unit emits a smooth, monotonous hum. If you hear a metallic clang, knocking or sharp clicks during operation, this may indicate wear of the bearings, destruction of the suspension or a defect in the valve group.
The second important parameter is the body temperature. Normally, the bottom of the compressor (where the oil is) and the top (outlet tube) should be hot, but not scalding. If the motor is so hot that it is impossible to touch it, and at the same time it constantly turns off due to thermal protection, this is a signal of a serious problem: an interturn short circuit, jammed mechanics or a freon leak.
⚠️ Attention: If the refrigerator motor hums for 5-10 seconds, then a click is heard and it goes silent, and after a minute the cycle repeats - Do not leave the refrigerator plugged in under any circumstances. This is a “peddling” job that will finish off the compressor in a few hours.
The third sign is the lack of cold when the engine is running. If the engine hums continuously without turning off for hours, but the temperature in the chambers does not drop, there may be a refrigerant leak or a blockage in the capillary system. The motor is idling, trying to pump up pressure that is not there.
☑️ Symptoms of compressor failure
Service life and wear factors
The average service life of a modern compressor is from 10 to 15 years, but the actual figure greatly depends depending on operating conditions. The main enemy of the motor is overheating. If the refrigerator is installed close to the wall, in a niche without ventilation or next to (stove, radiator), heat exchange is disrupted. The motor is forced to work with increased load, the oil loses its properties, and the insulation of the windings is destroyed faster.
The frequency of switching on also plays a role. If the refrigerator door is constantly slammed, or the door seal is worn out, the motor is forced to start more often than it should in the cycle. Each start is a peak load on the windings and mechanics. Starting current can be 5-7 times higher than the rated operating current, which gradually wears out the relay contacts and the motor itself.
The quality of electricity in the network is another critical factor. Low voltage causes the motor to work at its limit, not developing the required power, which leads to overheating. Increased voltage is dangerous for winding insulation. The use of surge protectors or stabilizers can significantly extend the life of the equipment.
Is it possible to repair the motor yourself?
The issue of repair motor-compressor is often a problem for equipment owners. It is important to clearly differentiate the concepts: replacing the start relay, thermal fuse or blower fan is a repair that can be done by a trained amateur with a multimeter and a screwdriver. However, replacing the compressor itself, soldering tubes, evacuation of the system and refilling with freon are complex technological processes that require special tools (vacuum pump, pressure gauge station, burner).
An attempt to replace the compressor yourself without the appropriate equipment is doomed to failure. Even if you manage to solder the new assembly, moisture and air will remain in the system, which will lead to the formation of an ice plug in the capillary after several hours of operation. In addition, modern refrigerants require high system cleanliness.
If the diagnostics showed an interturn short circuit of the windings or a mechanical knock inside the pressurized tank, the only way out is to replace the entire unit. The maintainability of hermetic compressors themselves in domestic conditions is zero. It is more economically feasible to replace the unit than to try to rewind the windings or change the piston, since the cost of the work and the risk of re-breakage are too high.
Why is the refrigerator motor hot?
The normal operating temperature of the compressor housing can reach 70-90 degrees Celsius. This is due to the fact that the motor is cooled by freon vapor and oil circulating inside the system. If the temperature is higher and there is a burning smell, this is a sign of overload or malfunction.
How much does it cost to replace a motor?
The cost consists of the price of a new compressor (depending on the brand and type) and the work of the technician. On average, replacement can cost from 30% to 60% of the cost of a new refrigerator, so in older models it is often more advisable to buy new equipment.
Can a motor burn out from a voltage surge?
Yes, a sharp surge in voltage can break through the insulation of the stator windings. Also dangerous is prolonged low voltage, in which the motor cannot gain speed and overheats until it burns out.