The heart of any modern refrigerator is the compressor, and the service life of the entire unit depends on its reliability. Many home appliance owners don't even think about what's inside that black metal cylinder until they experience a breakdown or a humming noise during operation. Understanding what materials the unit is assembled from helps you better navigate the characteristics of the device and assess the risks when purchasing.
The internal structure of a compressor is a complex engineering system, where each element is made of metal with certain physical properties. Steel, copper, aluminum and special alloys are the main components that ensure the compression of the refrigerant and its circulation through the system. The quality of these materials directly affects energy efficiency and noise levels.
In this article we will analyze in detail the design of piston and inverter motors, explain the role of windings and valves, and also find out why manufacturers choose such alloys to create pressure. This knowledge will allow you to distinguish high-quality equipment from budget analogues with a simplified design.
Materials of the housing and external protection
The external part of the compressor, which is often called the “pot,” is made of sheet cold-rolled steel. This material was not chosen by chance, since it must withstand internal pressure, vibration and temperature changes without deformation. The steel halves of the case are welded together, creating a sealed container inside which contains oil and moving parts of the mechanism.
The surface of the case is usually covered with heat-resistant black enamel. This paint performs a dual function: it protects the metal from corrosion and improves heat transfer, since the dark color helps radiate heat more efficiently into the environment. Inside the housing, at the bottom, there is always a small amount compressor oilthat lubricates the rubbing parts.
Tubes for connection to the refrigeration circuit are welded to the bottom of the steel housing. They can be made of steel or copper, depending on the model and manufacturer. It is important to note that the integrity of the housing welds is critical: any microcrack will lead to freon leakage and system failure.
⚠️ Attention: Never try to open the steel compressor housing yourself. Residual pressure may remain inside, and oil and refrigerant vapors may be flammable when in contact with an open flame or spark.
To attach the unit to the frame of the refrigerator, special claws are used, which are also part of the steel body. They are often equipped with rubber bushings or springs that dampen vibration transmitted from the running motor to the cabinet walls.
The heart of the mechanism: piston group and cylinders
The main working element of a classic compressor is the crank mechanism. It converts the rotational movement of the electric motor shaft into the translational movement of the piston. The shaft, connecting rod and piston are made of high-strength steel alloys, which have undergone special heat treatment to increase wear resistance. The cylinder in which the piston runs must have a perfectly smooth inner surface. For its manufacture, special cast iron or hardened steel is often used. The gap between the piston and the cylinder wall is minimal, but sufficient to create a thin oil film that prevents scuffing and overheating. steel alloys, which have undergone special heat treatment to increase wear resistance.
The cylinder in which the piston runs must have a perfectly smooth inner surface. For its manufacture, special cast iron or hardened steel is often used. The gap between the piston and the cylinder wall is minimal, but sufficient to create a thin oil film that prevents scuffing and overheating.
Valves are located at the end of the piston or in the cylinder wall. They control the flow of refrigerant, letting gas in when it expands and letting it out when it contracts. Modern valves are often made from stainless steel or special elastic alloys that can withstand millions of opening and closing cycles without loss of tightness.
Why does a piston group break?
The main reason for failure of a piston group is loss valve tightness or cylinder scuffing due to lack of oil. It is also possible for the connecting rod to be destroyed during a water hammer, when liquid freon enters the cylinder instead of gaseous one.
The quality of surface treatment of the piston group determines the life of the entire compressor. Cheap models may have less precise fitting of parts, which leads to lower performance and faster wear.
Electric motor and windings: copper vs. aluminum
The electrical part of the compressor is an asynchronous motor located in the lower part of the housing. The main element here is the stator windings, which create a magnetic field that rotates the rotor. Traditionally, electrolytic copper is used for the manufacture of windings due to its excellent conductivity and flexibility. However, in budget models of refrigerators, manufacturers are increasingly using aluminum windings. Aluminum is cheaper than copper, but has lower electrical conductivity and is less resistant to overheating. To compensate for this, the cross-section of the aluminum wire has to be increased, which is not always possible in limited space. electrolytic copper due to its excellent conductivity and flexibility.
However, in budget models of refrigerators, manufacturers are increasingly using aluminum winding. Aluminum is cheaper than copper, but has lower electrical conductivity and is less resistant to overheating. To compensate for this, the cross-section of the aluminum wire has to be increased, which is not always possible in limited space.
The motor rotor is assembled from electrical steel plates, which minimizes eddy current losses. The rotor shaft is a continuation of the crankshaft of the compressor, which ensures direct transmission of torque without the use of belts or gears.
The insulation of the windings is made of special varnishes and polymer materials that are resistant to freon and oil. Breakdown of this insulation leads to a short circuit and combustion of the engine, which is one of the most common reasons for repairs.
Starting and control system
A start-protective relay is used to start the engine and maintain its operation. In older models, these were mechanical devices that responded to current and heat. Modern compressors are increasingly using electronic control units, especially when it comes to inverter technologies.
The starting winding is turned on only at the moment of start to create the initial torque, after which it is turned off by a centrifugal switch or relay. The working winding remains energized throughout the operation of the refrigerator. The contact materials in the relay must be refractory to withstand sparking during switching.
In inverter models, the shaft rotation speed is controlled by complex electronics, which smoothly changes the voltage and frequency of the current. This allows you to avoid sudden surges in the load on the network and mechanical shocks at start, prolonging the life of the piston group.
⚠️ Attention: The parameters of the starting relay strictly correspond to the power of a particular engine. Installing a relay from a different model may result in the motor not starting or the winding burning out.
Thermal protection built into the relay or housing monitors the temperature of the windings. If the compressor overheats due to poor ventilation or refrigerant problems, the protection will break the power circuit, preventing a fire.
Comparison of materials in different types of compressors
Different types of compressors require the use of different materials and production technologies. Linear compressors, which have become widespread in LG technology, have a simplified design with fewer rubbing parts. They often use non-magnetic alloys to reduce resistance.
Inverter models, typical of Samsung and Bosch, involve the use of higher quality steel for the rotor and stator to ensure vibration-free operation at variable speeds. Conventional piston motors are more tolerant of the quality of materials, but are noisier in operation.
Below is a table comparing the key characteristics of materials in different types of units
| Compressor type | Winding material | Material piston | Noise level |
|---|---|---|---|
| Regular piston | Copper / Aluminum | Steel / Cast iron | High (30-40 dB) |
| Linear | Copper | Special alloy | Medium |
| Inverter | Copper | High-strength steel | Low (up to 20 dB) |
| Rotary | Copper | Steel | Medium |
The choice of materials directly affects the cost of the final product. The use of pure copper and high-quality steel increases the price, but guarantees a long service life. Budget options with aluminum windings and simplified alloys may last less, especially with unstable network voltage.
Design features of inverter models
Inverter compressors represent the pinnacle of evolution in refrigeration technology. Unlike conventional motors, which operate in an “on-off” mode, an inverter motor is able to smoothly regulate the speed of rotation of the shaft. For this purpose, the design uses neodymium magnets high power, mounted on the rotor.
The absence of starting currents and constant operation at low speeds reduces the wear of rubbing parts. However, this design requires more complex electronics and high-quality insulation of the windings, since they are exposed to high-frequency pulses from the inverter.
Bearings in inverter models are often made using special composite materials or have increased manufacturing precision to minimize noise during long-term operation. The oil in such systems may also have a synthetic base with improved properties.
Despite the complexity, these compressors consume less electricity. Their design is sealed, and maintenance at home is impossible - only a complete replacement of the unit.
Typical faults associated with materials
Understanding what the compressor is made of helps diagnose some problems. For example, if the windings are made of aluminum, they are more prone to burnout during power surges. Copper is more ductile and removes heat better, but it does not last forever.
Wear of the piston group often manifests itself in the form of metallic knocking or clanging. This means that the gaps between the parts have increased, or the valve has broken. In such cases, repair is often not economically feasible.
☑️ Signs of problems with the compressor
Freon leakage through microcracks in the body welds is another common problem associated with the quality of metal and welding. Corrosion of the external surface can also lead to through damage to the walls over time, especially in damp rooms.
⚠️ Attention: If you hear a burning smell or see sparking in the compressor area, immediately unplug the refrigerator. This may indicate an interturn short circuit of the windings.
In some cases, the cause of the breakdown is low-quality oil, which loses its properties at high temperatures, turning into a thick mass or acid that corrodes parts.
Can it be repaired or just replaced?
The issue of compressor repair often arises for owners of expensive equipment. Theoretically, it is possible to replace the start relay or even rewind the motor. However, in practice the sealed case makes high-quality repairs at home impossible.
To open the case, special equipment is required for cutting and subsequent welding, as well as a vacuum pump for refilling the system. The cost of such work often exceeds the price of a new compressor. Therefore, most service centers only offer replacement of the entire assembly.
The exception is when the problem lies in an external relay or wiring. These elements are easily replaced without compromising the tightness of the system. If the winding or piston group is damaged, replacement is inevitable.
Modern compressors are designed as maintenance-free units. Their resource is designed for the entire service life of the refrigerator, which is usually 10-15 years. After this period, it is more advisable to replace the entire unit.
Why are compressors made of steel and not plastic or aluminum?
Steel is necessary to ensure tightness under pressure and strength during vibration. Plastic will not withstand pressure and temperature, and thin aluminum can become deformed. In addition, steel better dampens the noise of the mechanism.
Can the compressor housing rust?
Yes, if the enamel layer is damaged or there is high humidity in the room, the steel may corrode. Particularly vulnerable are welds and pipe fastenings. Rust can lead to freon leakage over time.
What is the difference between copper and aluminum windings?
Copper has better electrical conductivity and heats up less, which increases service life. Aluminum is cheaper, but requires a larger wire cross-section and is more sensitive to overloads and oxidation at the contact points.
How much does a standard compressor weigh?
The weight of a typical household compressor for a refrigerator with a capacity of up to 350 liters ranges from 8 to 12 kilograms. The weight depends on the amount of steel and copper used in the structure.
Is it dangerous to touch a running compressor?
Yes, the temperature of the housing of a running compressor can reach 70-90 degrees Celsius. Prolonged contact may cause burns. In addition, there may be dangerous voltage on the case in the event of an insulation breakdown.