The refrigerator is one of the most important household appliances in the house, and its “heart”, of course, is the compressor. It is this unit that creates the necessary pressure for the circulation of the refrigerant, ensuring cooling of the chambers. Many owners don’t even think about what’s inside the sealed metal casing until the device breaks down or requires replacement.
Understanding how a refrigerator motor works helps not only in diagnosing malfunctions, but also in choosing the right new equipment. Modern models differ significantly from units produced several decades ago. The differences lie in the materials, types of motors and methods of speed control.
In this article we will analyze in detail the internal structure of the compressor, consider the physical processes that occur during gas compression, and compare different types of structures. You'll learn why some models are quieter and others use less power. We will also touch on safety issues when working with high pressure.
The main function and principle of operation of the compressor
The main task of the compressor in the cooling system is to create a pressure difference. It draws gaseous refrigerant from the evaporator, where it has already absorbed heat from the refrigeration chamber. After this, a compression process occurs, as a result of which the temperature of the gas increases sharply.
Under high pressure, heated freon is sent to the condenser (heat exchanger on the rear wall). Here the gas gives off heat to the environment and condenses, turning into a liquid state. The cycle is completed when the liquid refrigerant passes through the capillary tube and again enters the evaporator, where it boils at low pressure.
It is important to understand that refrigerator compressor is not just a pump, but a complex thermodynamic mechanism. It ensures constant circulation of the working fluid in a closed circuit. The efficiency of the entire system directly depends on the tightness and performance of this unit.
⚠️ Attention: Inside the compressor and pipe system there is refrigerant under pressure. Opening the casing on your own or cutting the tubes without special equipment and skills can lead to injury or poisoning.
The compression process is accompanied by significant heating of the parts, so most household compressors are equipped with a passive or active cooling system. The oil in the crankcase not only lubricates the rubbing parts, but also helps remove excess heat.
Design of a piston compressor
Until recently, the most common type of engine in household appliances remained a piston unit. Its design is relatively simple and reliable, as evidenced by the long service life of many models. The basis of the design is an electric motor, the shaft of which is connected to the crankshaft of the compressor part.
Inside a sealed casing filled with inert gas or freon, the main working elements are located. Crank mechanism converts the rotational movement of the engine shaft into the translational movement of the piston. It is the piston, moving up and down, that compresses the gas.
The valve group is located on top of the cylinder. It consists of inlet and outlet valves, which open and close under the influence of pressure differences. This ensures that the refrigerant moves strictly in one direction, preventing reverse gas flow.
All these mechanics are immersed in oil, which splashes when the shaft rotates. Oil is necessary to reduce friction and create additional tightness between the piston and cylinder walls. The quality of the lubrication is critical to the longevity of the unit.
Differences between linear and inverter motors
Technological progress has led to the emergence of more efficient motors. If traditional models operate on the principle of “turned on - cooled - turned off”, then modern inverter systems support constant operation at different speeds. This allows you to avoid sudden temperature changes.
In inverter compressor there is no rigid mechanical connection between the rotating shaft and the piston in the classical sense. A linear actuator is often used, where the piston moves due to electromagnetic forces. The absence of rubbing parts in the drive unit significantly reduces the noise level.
Linear compressors, which can often be found in LG or Samsung models, have an even more simplified design. The piston moves back and forth due to changes in the magnetic field in the coil. This eliminates the need for a crank mechanism.
Advantages of inverter technology
Inverter motors consume less electricity, since they do not waste energy on constant starting currents. They are quieter and provide more accurate temperature control, which extends the shelf life of food.
Despite the advantages, inverter systems are more sensitive to voltage fluctuations in the network. For their stable operation, the use of high-quality stabilizers or uninterruptible power supplies is often required. Repairing such components is also more expensive.
Starting system and electrical circuit
Starting a single-phase asynchronous motor, which is used in most compressors, requires the creation of torque. For this purpose, a starting winding is used, which is switched on only for a short time. This process is controlled by a start-up relay.
In older models, relays with a posistor were often used. When voltage is applied, the posistor heats up and changes its resistance, opening the starting winding circuit. More modern designs may use electronic control units.
The protective relay plays a critical role in the safety of the device. It opens the power circuit if the current in the windings exceeds the permissible values or if the temperature of the motor housing becomes too high. This prevents the windings from burning out.
☑️ Diagnostics of the electrical part
The electrical circuit of the engine usually includes two main windings: working and starting. The working winding has a larger wire cross-section and lower resistance; it is constantly involved in the work. The starting winding is turned on only for a few seconds to spin up the shaft.
Table of characteristics of compressor types
To compare different types of engines, it is convenient to use summary data. They allow you to quickly assess the advantages and disadvantages of each design in the context of operation and maintenance.
| Parameter | Piston | Inverter | Linear |
|---|---|---|---|
| Noise level | Medium / High | Low | Very Low |
| Energy consumption | Standard | Economy | Economical |
| Service life | 7-10 years | 10-15 years | 10-15 years |
| Sensitivity to networks | Low | High | High |
| Repair cost | Low | High | High |
The table shows that modern technologies are superior in terms of noise and energy consumption. However, the simplicity and low cost of servicing piston models make them still popular in the budget segment of equipment.
Types of refrigerants and their effect on the device
The design of the engine and the entire refrigeration system is closely related to the type of refrigerant used. In older models, freon was widely used, which had excellent refrigeration properties, but was recognized as harmful to the ozone layer. Modern engines work with refrigerants R12 (freon), which had excellent refrigeration properties, but was found harmful to the ozone layer.
Modern engines work with coolants R134a or R600a (isobutane). Isobutane is an explosive gas, which imposes additional requirements on the tightness of the system and the quality of the compressor assembly. The gas dose in such systems is much smaller, and the pressure is lower.
The use of different types of freons requires the use of different oils. Mineral oils used with R12 are not suitable for synthetic refrigerants. Systems with R134a and R600a use polyester oils (POE), which are highly hygroscopic.
⚠️ Attention: Polyester oils quickly absorb moisture from the air. When repairing such systems, you cannot keep the circuit open for a long time, otherwise the oil will lose its properties and acid will form in the system.
The transition to new refrigerants required a change in the design of the compressors. The reliability of the insulation of the motor windings has increased, since new freons and oils can be more chemically aggressive to some materials.
Diagnostics of engine faults
It is possible to determine that the refrigerator engine is faulty by a number of signs. The most obvious is that the refrigerator has stopped freezing, and the compressor either does not start or runs continuously without turning off. Increased noise or vibration may also be observed.
If the motor hums, but does not start, and after a few seconds the relay clicks, this often indicates a jammed piston group or an interturn short circuit in the windings. In some cases, installing a more powerful starting capacitor helps, but this is a temporary solution.
For accurate diagnostics, you need to ring the windings with a multimeter. The resistance between the contacts must be within certain limits (usually from 10 to 30 Ohms for the working winding and higher for the starting winding). A short to housing (resistance 0 Ohm) indicates a burnt-out motor.
It is also worth paying attention to the color of the gas leaving the system. If, when the pressure is released, black smoke comes out or the oil has a burnt smell, it means that an insulation breakdown has occurred inside the engine and the windings have burned out. In this case, a complete flushing of the system is required.
Safety and maintenance features
Working with refrigeration compressors requires compliance with strict safety measures. Firstly, there is high pressure inside the system. Even when turned off, residual pressure may remain there, dangerous to the eyes and skin.
Secondly, electrical safety. The engine runs on a 220V network, and at the moment of starting the currents can be significant. All replacement or repair work must be carried out with the device completely disconnected from the network.
Disposal of old compressors also has its own characteristics. You can't just throw them in the trash. Residual refrigerant and technical oil can be harmful to the environment. They should be taken to special collection points for scrap metal or household appliances.
Is it possible to repair a hermetic compressor?
Theoretically, it is possible by cutting the casing with a grinder, but in practice this is not economically feasible. Factory sealing and balancing at home is not possible. It is easier and more reliable to replace the entire unit.
Why is the compressor hot to the touch?
Heating to 60-90 degrees Celsius is the norm for a working compressor. This is the result of gas compression and the operation of an electric motor. You should sound the alarm if it becomes red-hot or has a burning smell.
How often do you need to change the compressor?
With proper operation and stable mains voltage, the compressor lasts the entire life of the refrigerator (10-15 years). Frequent breakdowns indicate problems with the electrical or cooling system.
Does tilting the refrigerator affect engine operation?
Yes, strong (more than 40 degrees) can lead to oil draining from the compressor into the system circuit. This disrupts lubrication and can cause water hammer during startup. After transportation, the refrigerator needs to stand upright for several hours.
What is “dry running” of a compressor?
This is the operation of the engine without a sufficient amount of refrigerant or oil. In household hermetic compressors, this is almost impossible without freon leakage, which will lead to overheating and rapid failure.