The refrigerator is one of the most important electrical appliances in every home, ensuring the safety of food. The heart of this complex system is compressorwhich is often called a motor-compressor. It is this unit that creates the pressure necessary to circulate the refrigerant in a closed circuit, forcing it to release heat to the environment.
Many users perceive the refrigerator as a “black box”: plug it in and it works. However, understanding how a refrigerator compressor worksallows you to quickly diagnose faults and avoid costly mistakes during operation. The internal structure of this unit is a balance of mechanical strength and precision engineering.
In this article we will examine in detail the anatomy of the compressor, look under its metal casing and study the processes occurring inside. Knowledge of the operating principles of the piston group and valve system will help you better understand the causes of noise, vibration or lack of cooling.
General design and principle of operation
From a design point of view, a household compressor is a sealed unit that combines an electric motor and a mechanical compressor part. This entire mechanism is enclosed in a durable steel case, which protects internal parts from dust, moisture and mechanical damage. The principle of operation is based on the compression of gaseous refrigerant and its pumping through the condenser.
An electric motor located inside converts electrical energy into rotational movement of the shaft. This movement is transmitted to the crank mechanism, which transforms the rotation into the translational movement of the piston. It is the piston, moving up and down inside the cylinder, that creates areas of vacuum and high pressure.
It is important to note that modern models may differ in the type of drive. Traditional piston units are still the most common due to their reliability and maintainability. However, there are also inverter and linear models on the market, where the design is significantly simplified or modified to increase energy efficiency.
⚠️ Attention: The sealed compressor casing cannot be opened at home without special equipment. Violation of the tightness will allow moisture and oxygen to enter the system, which will cause instant corrosion and failure of the unit.
Oil circulation inside the housing is also a critical part of the design. The oil not only lubricates the rubbing parts, but also participates in sealing the gaps between the piston and the cylinder walls, and also removes some of the heat generated during operation.
Electrical part: stator and rotor
Inside the sealed casing there is an electric motor, which is the driving force of the entire process. It consists of two main elements: a stationary stator and a rotating rotor. The stator is attached to the inner walls of the casing or suspension system, and the rotor is pressed onto the compressor shaft.
The stator windings are made of copper wire and insulated with special varnishes that can withstand high temperatures and the aggressive environment of freon. When voltage is applied, a magnetic field appears in the windings, which causes the rotor to rotate. To start the engine, a starting winding and a starting relay are used, which turns it off after a set of revolutions.
- ⚡ Working winding - the main element that creates torque during normal operation of the compressor.
- 🔄 Starting winding - turns on only for a short time to overcome the inertia of the stationary piston.
- 🛡️ Thermal element protection - a bimetallic plate that opens the circuit when the windings overheat or current overload.
In modern inverter models design electrical part may differ. Frequency control is used here, which allows you to change the speed of rotation of the shaft, which makes the operation of the refrigerator quieter and more economical. However, the basic principle of the interaction of magnetic fields remains unchanged.
The reliability of the electrical part directly depends on the quality of the voltage in the network. Voltage surges can lead to breakdown of the winding insulation or sticking of the starting relay contacts, which is a common cause of equipment failure.
Mechanical part: cylinder and piston
The heart of the mechanical part is the cylinder-piston group. This is the most loaded unit, experiencing colossal pressures and temperatures. The compressor shaft, rotating, sets the connecting rod in motion, which, in turn, pushes the piston.
The piston performs reciprocating movements inside the cylinder. When moving downwards, a vacuum is created inside the cylinder, and gaseous refrigerant is sucked through the inlet valve. When moving upward, the gas is compressed and its pressure increases sharply, after which it is pushed through the discharge valve into the condenser.
The manufacturing precision of these parts is extremely high. The gap between the piston and the cylinder wall is a fraction of a millimeter, which provides the necessary compression without the use of additional seals, which would quickly wear out under such conditions. For lubrication, a special compressor oilis used, which is sprayed inside the housing.
⚠️ Attention: An attempt to start the compressor without oil or with a low oil level will lead to scuffing on the cylinder mirror and instant jamming of the piston.
The materials from which the piston and cylinder are made are selected to have a minimum coefficient of friction and high wear resistance. Special cast iron or steel with a special hardening of the surface is often used.
Valve system and flow distribution
The key element that ensures the unidirectional movement of the refrigerant is the valve assembly. It is located directly at the end of the cylinder and consists of inlet and discharge valves. These parts are thin elastic plates that work like membranes.
When the piston goes down, the pressure in the cylinder drops, and atmospheric pressure (pressure in the suction line) presses the inlet plate, allowing gas access. As the piston moves upward, the pressure in the cylinder increases sharply, the inlet valve closes, and the discharge valve opens, releasing compressed gas into the system.
The efficiency of the entire refrigerator depends on the condition of these thin plates. If the valve has lost its tightness or is broken, the compressor will run “idle,” pushing gas back and forth without creating the necessary pressure. As a result, the refrigerator will stop freezing, although the motor will hum.
- 💨 Inlet valve - lets cold low pressure gas through from the evaporator.
- 🔥 Discharge valve - releases hot compressed gas into the condenser.
- 🔩 Valve plate —the base on which the plates are attached and which separates the high and low pressure zones.
Why do valves break?
The main reason for valve failure is water hammer. This happens if liquid freon or oil enters the cylinder in large quantities. Liquid, unlike gas, is not compressed, and during the stroke of the piston a huge force is generated that breaks the valve plates or even the piston itself. This often happens when the refrigerator is not refilled correctly or is left idle for a long time in a cold room.
In some designs, the valves are made in the form of tongues, in others - in the form of rings. Their elasticity and accuracy of fit are critical to creating compression.
Suspension system and sound insulation
The compressor creates strong vibration during operation. To prevent it from being transmitted to the refrigerator body and causing a loud hum, the motor is suspended inside the casing on a special spring system. Typically, three or four powerful springs are used, located around the perimeter.
This suspension works as a shock absorber, dampening vibrations. The springs are made of special steel, which does not lose its properties for years. However, when transporting the refrigerator lying down or at a strong tilt, the springs may jump off or become deformed, which will cause the compressor to start hitting the walls of the casing.
The inner walls of the casing are often covered with noise-absorbing material or have a special structure that dampens sound waves. In addition, the refrigerant itself and the oil circulating inside also help reduce noise levels by enveloping the moving parts.
⚠️ Attention: If after transportation you hear a metallic clanging sound when starting, the suspension system is probably malfunctioning. Operation in this mode will lead to breakage of the tubes inside the casing.
The quality of the suspension directly affects the service life of the unit. Constant vibration can lead to metal fatigue and the formation of microcracks in welds or tubes.
Types of compressors: differences in design
Although the basic principle of gas compression remains common, the design of compressors can vary significantly. Understanding these differences is important when choosing equipment or planning repairs. The main types found in everyday life are piston, inverter and linear.
Traditional piston compressors operate on the principle described above: there is a cylinder, a piston and a crankshaft. They are reliable, but have a number of moving parts that are subject to wear. Inverter models can also be piston, but their engine is able to smoothly change the rotation speed, avoiding constant on and off cycles.
Linear compressors, popular in technology LG and some models of other brands, are designed differently. They do not have a rotating shaft or connecting rod. The piston is driven by electromagnetic forces, making linear movements. This reduces the number of rubbing parts and increases efficiency.
| Parameter | Piston (Normal) | Inverter | Linear |
|---|---|---|---|
| Operating principle | Shaft rotation, reciprocating motion | Smooth change in rotation speed | Electromagnetic linear motion |
| Noise level | Medium / High | Low | Very low |
| Energy consumption | Standard | Economical | Highly efficient |
| Resource | 7-10 years | 10-15 years | 10-15 years |
The choice of compressor type affects not only the price of the refrigerator, but also the nature of its operation. Inverter and linear models are quieter and create fewer temperature changes inside the chambers.
Diagnostics and typical faults
Knowing the internal structure, it is easier to understand the causes of breakdowns. If the compressor hums but does not start, the problem may be a jammed piston group or a faulty start relay. The absence of noise when the light is on indicates an open circuit or burnt out windings.
Loss of compression is a common problem. This means that the mechanical part is intact, the motor is spinning, but the valves do not hold pressure. In this case, the refrigerator runs constantly, but does not cool. Repair in this case requires replacing the compressor, since opening the hermetic block is not economically feasible.
- 🔊 Loud knocking - a sign of broken bearings, a slipped suspension spring or water hammer.
- 🔥 Strong heating of the housing - may indicate an interturn short circuit or operation without sufficient quantity refrigerant.
- 💧 Oily spots - indicates depressurization of the casing or pipes, which requires immediate intervention.
For accurate diagnosis, the technician uses a pressure gauge station to measure the discharge pressure and a multimeter to check the winding resistance. Visual inspection is also important: swelling of the casing or traces of soot indicate serious internal problems.
☑️ Signs of a working compressor
Timely contacting specialists when the first signs of a malfunction can save the compressor from complete destruction and keep food in the refrigerator.
FAQ: Frequently asked questions
Is it possible to replace the compressor with an analogue from another manufacturer?
Yes, this is often possible, but it requires a professional approach. It is necessary to take into account the overall dimensions, power, refrigerant (R134a, R600a), oil type and location of the starting fittings. A simple one-to-one replacement is rare; alteration of copper tubes and electrical circuits is often required.
Why does the compressor get very hot during operation?
Heating to 60-90 degrees Celsius is the norm for many models, since gas compression and friction occur inside. However, if the body is hot to the point where you cannot touch it with your hand, or the refrigerator does not turn off for days, this is a sign of a malfunction: a freon leak, a clogged capillary, or problems with the windings.
What do the markings HBP, LBP, MBP on the compressor mean?
These abbreviations indicate the temperature conditions applications. LBP (Low Back Pressure) - for low pressure, used in refrigerators and freezers. HBP (High Back Pressure) - for high pressure, used in air conditioners. MBP - medium pressure. Installing the wrong type of compressor will lead to its rapid breakdown.
Is it possible to repair the compressor yourself?
High-quality repair of the compressor is possible only in the factory using vacuum pumps and welding in an inert gas environment. At home, you can only replace external elements: the start relay, capacitor or filter drier. Opening the casing will lead to moisture entering and destruction of the system.
How long should the compressor operate normally?
The operating time depends on the load of the refrigerator, the ambient temperature and the set temperature. Typically the operating cycle is from 10 to 20 minutes, followed by a pause. In hot weather or when fully loaded with warm products, the operating time can increase significantly.