The refrigerator is one of the few household appliances that operates continuously 24 hours a day, ensuring the safety of food. The heart of this complex cooling system is the compressor, often called a motor or pump in everyday life. It is he who is responsible for the circulation of the refrigerant in a closed circuit, creating the necessary pressure to change the temperature of the substance.
Understanding how this unit functions will help the owner of household appliances to notice malfunctions in time, reduce energy consumption and avoid costly repairs. The operating principle is based on the physics of phase transitions of gases and liquids, where changes in pressure directly affect the boiling point and condensation point of the working fluid.
In this article we will analyze in detail the internal structure of various types of compressors, consider their differences and discuss the nuances of operation. You will find out why the unit can hum, how often it should turn on and what happens inside the tubes at the moment of startup.
The basic principle of operation of the refrigeration circuit
The cooling process begins not with cold, but with the extraction of heat from the chambers of the refrigerator. Compressor sucks in gaseous refrigerant (freon) from the evaporator, where it has already absorbed the thermal energy of the products. At this stage, the gas has low pressure and temperature.
After suction, the gas is compressed, which leads to a sharp increase in its temperature and pressure. Hot steam is fed into a condenser (usually a grate on the back wall or hidden in the side walls), where it cools to room temperature and turns into liquid.
Next, the liquid freon passes through a filter drier and a capillary tube, where its pressure drops sharply. Once in the evaporator, the refrigerant boils again at low temperatures, actively removing heat from the interior of the chamber. The cycle is completed when the gas returns to the suction pipe again.
Design of linear and inverter compressors
In the modern household appliances market, two main types of motors predominate, differing in design and control principle. Classic linear compressor works on the “on-off” principle. It starts at full power, cools the chamber to the set temperature, and then turns off completely until the next temperature increase.
Inverter models function differently. After the initial cooling, they do not stop, but only reduce engine speed, maintaining the temperature within a narrow range. This is achieved through a frequency converter (inverter), which smoothly regulates the rotor speed.
- 🔹 Linear type: characterized by cyclic noise when starting and stopping, higher peak current consumption.
- 🔹 Inverter type: operates almost silently, saves up to 30% of electricity, wears less mechanically.
- 🔹 Electronic control: in inverters a complex board is responsible for accuracy, in linear ones - a simple thermal relay.
It is worth noting that inverter systems are sensitive to voltage drops in the electrical network. If the light often “jumps” in your home, it is recommended to use a voltage stabilizer to protect expensive control electronics.
Detailed design of the electromechanical part
A complex mechanism is hidden inside the sealed metal casing. The basis is an electric motor, the rotor of which is rigidly connected to the compressor shaft. When voltage is applied to the stator windings, a magnetic field is created that rotates the rotor.
The crank mechanism converts the rotational movement of the shaft into the translational movement of the piston. The piston, moving up and down in the cylinder, alternately creates a vacuum (to suck in gas) and pressure (to push it out). All rubbing parts operate in an oil bath, which also helps remove heat.
Why can’t you open the compressor casing?
Inside the casing, excess pressure of an inert gas is created, and there are also oil vapors. Opening will lead to depressurization, loss of oil and the need for complex refilling of the system, which is not economically feasible.
An important element is the starting system. For single-phase motors, a starting relay is used, which briefly supplies current to the starting winding to spin the rotor. After a set of revolutions, the relay opens the starting winding circuit, and the engine runs on the main one.
| Component | Function | Material of execution |
|---|---|---|
| Stator | Creation of magnetic fields | Copper wire, electrical steel |
| Rotor | Shaft rotation | Steel, aluminum alloy |
| Piston | Compression refrigerant | Cast iron, steel |
| Valves | Flow direction control | Spring steel |
The role of refrigerant and thermoregulation
The efficiency of the entire system directly depends on the properties freon. This substance must have a low boiling point at atmospheric pressure. In modern refrigerators, the gases most often used are R600a (isobutane) or R134a.
Temperature control is carried out by thermostat or an electronic sensor. The thermostat mechanically opens the contacts of the compressor power circuit when the temperature in the chamber reaches a predetermined minimum. Electronic systems use data from thermistors to send signals to the control board.
If the thermoregulation system fails, the compressor can run without stopping. This leads to freezing of the evaporator and excessive cooling of the products, even to the point of spoilage. At the same time, insufficient work will lead to defrosting of the contents.
⚠️ Attention: Independent replacement of the refrigerant is prohibited by the legislation of many countries and requires special equipment for evacuation of the system. An attempt to refuel “by eye” will lead to compressor failure.
Typical malfunctions and their symptoms
Diagnosis of problems with a compressor often begins with an analysis of the sounds it makes. Humming, knocking or complete silence when plugged in can indicate varying degrees of failure. The most common problem is the failure of the start relay.
If you hear a characteristic click, a hum for 2-3 seconds and a second click, after which the refrigerator goes silent, this is a sign that the engine cannot start. The thermal protection relay is activated, turning off the power to prevent the windings from burning out.
- 🔸 Case overheating: if the motor casing is hot to the point where it cannot be touched, this may indicate an interturn short circuit.
- 🔸 Continuous operation: if the refrigerator hums without interruption and does not turns off, check the tightness of the doors and the integrity of the seal.
- 🔸 Oil stains: the appearance of oil under the refrigerator may indicate depressurization of the compressor crankcase.
☑️ Diagnostics noise
It is also worth considering that new models may make specific sounds of gurgling or liquid flowing. This is normal and indicates the movement of refrigerant through the system, especially in models with No Frost.
The influence of operating conditions on the resource
The service life of a compressor directly depends on the conditions in which it has to work. The critical factor is the ambient temperature. If the refrigerator is installed close to a hot wall or in direct sunlight, the heat transfer efficiency of the condenser decreases.
As a result, the compressor is forced to work longer and harder to maintain the set temperature inside the chambers. This leads to overheating of the oil, loss of its lubricating properties and accelerated wear of rubbing parts.
Another important aspect is the frequency of door openings and the volume of loaded products. Loading a large amount of warm products creates a peak load on the system. Evaporator It becomes covered with an ice crust, heat exchange is disrupted, and the motor wears out.
Is it possible to transport the refrigerator lying down?
Technically it is possible, but with caution. Oil from the compressor may leak into the refrigerant circuit. After transportation in a horizontal position, you must allow the refrigerator to stand vertically for at least 4-6 hours before turning it on.
⚠️ Attention: Do not install the refrigerator in unheated rooms (balconies, garages) in winter. The oil in the compressor thickens in the cold, which, when started, can lead to jamming of the mechanism and breakage of the valves.
Prevention and extension of service life
In order for the compressor to serve as long as possible, it is enough to follow simple operating rules. Defrost the refrigerator regularly (if it is not a No Frost model), removing ice build-ups that act as a heat insulator and interfere with effective cooling.
Keep the condenser clean. Dust, animal hair and dirt that settle on the grille at the back or bottom of the refrigerator will drastically reduce heat output. It is recommended to clean the rear wall with a vacuum cleaner or soft brush once every 6-12 months.
Check the integrity of the rubber door seal. If it does not fit tightly, warm air constantly enters the chamber, forcing the compressor to work almost non-stop. The check can be carried out by a simple test with a sheet of paper sandwiched between the door and the body.
Why is the compressor hot to the touch?
During the process of gas compression, the temperature rises significantly. The normal temperature of the casing is up to 70-90 degrees Celsius. If it gets hotter or, conversely, remains cold when the engine is running, this is a sign of a malfunction.
Is it possible to replace a linear compressor with an inverter one?
Theoretically it is possible, but in practice it is extremely difficult and expensive. It will be necessary to replace not only the motor, but also the entire control system (board), as well as reconfigure the operating parameters. Often the cost of such a modification exceeds the price of a new refrigerator.
How long does a compressor last on average?
The average service life of modern compressors is 10-15 years. Inverter models, due to the absence of constant starting loads, can theoretically last longer, up to 20 years, provided there is a stable voltage in the network.