For most users, the refrigerator is just white a drawer that hums in the kitchen and keeps food fresh. However, inside this unit hides a complex engineering system, the heart of which is the compressor, or, as it is often called in everyday life, motor. It is this unit that is responsible for circulating the refrigerant, creating the necessary pressure to cool the chambers. When the device stops working or starts making strange sounds, a natural question arises about what exactly is broken and whether it can be fixed.
Understanding the internal structure of the compressor is necessary not only for professional craftsmen, but also for equipment owners who want to understand the causes of the breakdown or estimate the cost of repairs. Sealed casing hides numerous high-pressure parts. In this article, we will look “under the hood” of this mechanism to examine in detail its design, principle of operation and the main components that provide cold air in your home.
It is important to note right away that modern household compressors are most often sealed units. This means that they are not intended for disassembly at home. A rarefied atmosphere or filling with inert gas is maintained inside the case to prevent oxidation of parts and drainage heat. Violation of the seal when attempting to open it usually leads to the final failure of the unit, therefore all descriptions below are for informational and diagnostic purposes.
Principle of operation and general design
A refrigerator compressor is an electromechanical pump that compresses and pumps gaseous refrigerant along the system circuit. The process begins by applying electrical current to the motor windings, which causes the rotor to rotate. This rotation is converted into a reciprocating motion of the piston inside the cylinder. It is this mechanical work that creates the pressure difference necessary for freon phase transitions.
All this mechanics is enclosed in a durable steel casing that performs several functions. Firstly, it seals the system, preventing refrigerant leakage and moisture getting inside. Secondly, the housing serves as a muffler, reducing the noise level from moving parts. A specific atmosphere reigns inside the casing, often saturated with oil vapor, which ensures lubrication of rubbing parts.
⚠️ Attention: Inside the compressor housing, even after a long period of inactivity, a high residual pressure can remain. An attempt to open a weld without special equipment and releasing pressure can lead to explosive depressurization and injuries.
The design of most household models is of the piston type, although in recent years inverter linear compressors have been gaining popularity. In the classic version, the engine shaft is directly connected to the crank mechanism. This circuit has been tested for decades and is highly reliable, despite the presence of many moving elements.
Electrical part: motor and starting equipment
The basis of the “motor” is an asynchronous type electric motor. It consists of a stationary stator with windings and a rotating rotor. To start the engine and maintain its operation, two windings are used: starting and working. The starting winding is turned on only for a short time at the moment of start, helping to overcome inertia, after which it is turned off by a special relay.
The electrical part also includes a protection system. A thermal relay or a posistor (PTC element) monitors the temperature of the windings. If the motor overheats due to a power surge or a jammed mechanism, the circuit breaks, preventing the insulation from burning and causing a fire. In modern inverter models, the rotation speed is controlled by complex electronics located on an external board, but there are also sensors inside the casing.
- 🔌 Contact group - provides voltage supply to the windings through terminals hermetically sealed into the housing.
- 🛡️ POSISTOR —a thermal switch that opens the circuit of the starting winding when heated.
- ⚙️ Protection relay —a mechanical or electronic element that turns off the motor in case of current overload.
Diagnostics of the electrical part often begins with checking the resistance of the windings with a multimeter. Normal resistance values indicate the integrity of the wire, while a short circuit or break indicates the need to replace the unit.
Why does the starting relay burn out?
Frequent power surges or attempts to start with a jammed piston lead to overheating of the relay contacts. It can “stick”, leaving the starting winding on, which causes rapid overheating and melting of the insulation in a matter of minutes.
Mechanics: cylinder, piston and crankshaft
The heart of the mechanical part is the crank mechanism. It converts the rotational movement of the electric motor shaft into the translational movement of the piston. Crankshaft (crankshaft) has an eccentric on which the connecting rod is placed. As the shaft rotates, the connecting rod causes the piston to move up and down inside the cylinder.
The cylinder and piston are made to minimum tolerances. The gap between them is critical: it must be sufficient for free movement, but small enough to minimize gas blow-by. There are compression ringsinstalled on the piston, which ensure a tight fit to the cylinder walls. Wear of these rings is one of the common causes of loss of compressor performance.
Valve plates are located at the top of the cylinder. These are thin steel petals that act as check valves. They open and close under the influence of gas pressure, ensuring the movement of freon in only one direction: from the suction line to the discharge line. Damage or breakage of these plates often leads to the compressor humming but not pumping.
☑️ Signs of mechanical failure
Lubricating system and oil pump
Unlike automobile engines, where oil circulates under pressure through channels, In hermetic refrigerator compressors, capillary rise is often used. At the lower end of the crankshaft there is often a screw thread or a special tube, which, when rotated, captures oil from the crankcase and delivers it upward to the rubbing pairs. splashing or capillary rise. At the lower end of the crankshaft there is often a screw thread or a special tube, which, when rotated, captures oil from the crankcase and delivers it upward to the rubbing pairs.
Oil in the refrigerator performs a triple function: lubrication, cooling and sealing gaps. It must have the following properties: not freeze at low temperatures (in the evaporator) and not oxidize upon contact with the refrigerant. Typically, synthetic or mineral oils of the brand POE (polyester) or PAGare used, depending on the type of freon.
The oil level is strictly regulated by the manufacturer. Lack of lubrication leads to scoring on the cylinder and jamming. Excess oil is dangerous because it can enter the cooling circuit (condenser and evaporator), forming an oil film on the walls of the tubes. This sharply reduces heat transfer and the operating efficiency of the entire refrigerator.
⚠️ Attention: It is strictly forbidden to mix different types of oils or use oils not intended for refrigeration equipment. Conventional motor oil will harden in the system or enter into a chemical reaction with the refrigerant, destroying the compressor.
Table: Main components and their functions
To systematize the information, consider the main components hidden inside the casing and their purpose. This table will help you understand which element is responsible for what in the general scheme of operation.
| Component | Location | Main function |
|---|---|---|
| Stator and rotor | Lower part | Conversion of electrical energy into rotational motion |
| Crankshaft | Central axis | Transmission of rotation and its conversion into translational motion |
| Piston and cylinder | Upper part | Direct refrigerant compression |
| Valve plates | Cylinder head | Adjusting the direction of gas flow (inlet/outlet) |
| Suction tube | Output | Intake of freon gas from the evaporator |
Each of these elements is made of special alloys that are resistant to exposure to refrigerants and oils. Steel, copper and special composites are selected to minimize thermal expansion and wear. An imbalance in any of these systems leads to dysfunction of the entire unit.
Typical malfunctions of internal parts
Understanding what is inside helps to diagnose a breakdown based on indirect signs. For example, if the compressor tries to start, hums, but after a few seconds it clicks and goes silent, most likely the problem is in mechanical jamming the piston group or failure of the start relay.
Interturn short circuit in the motor windings is another a common problem. In this case, the engine may hum, overheat and knock out the circuit breaker. Repairing windings inside a sealed housing is technically difficult and economically impractical, so such units must be completely replaced. There is also a broken connecting rod, which leads to a strong knock and lack of pressure in the system.
- 🔨 Breakage of a connecting rod —accompanied by a loud knock and lack of compression.
- 🔥 Winding combustion —a characteristic burning smell (if there is a leak) or knocking out plugs.
- ❄️ Moisture freezing —water entering the system leads to the formation of ice plugs in the capillaries.
It is important to note that many malfunctions inside the motor are the result of external factors: voltage surges, improper operation or prolonged downtime. Regular maintenance and the use of a voltage stabilizer can extend the life of internal components.
Tightness and safety issues
Question Tightness comes first in the design of the compressor. The body is welded at the factory, and any attempts to open it will violate the factory geometry and balancing. Pressure is created inside, which can increase significantly when heated. That is why you can often see warning stickers on the case about the prohibition of opening.
In addition, there is oil inside, which, upon contact with open air and moisture, begins to oxidize, forming acid. This acid then destroys the winding insulation and metal parts. Therefore, even with a successful oil change or mechanical repair, it is almost impossible to assemble a unit with factory sealing quality at home.
⚠️ Attention: When working with a dismantled compressor, never turn it on without the suction and discharge pipes connected. This will disrupt the engine cooling system (gas cools the windings) and can lead to instant overheating and an explosion of oil vapor.
Modern environmental standards also dictate their conditions. Refrigerants used in refrigerators can be flammable (for example, isobutane R600a). If the system is depressurized and there is a spark (for example, from a relay or soldering), there is a risk of ignition. Therefore, work should be carried out in well-ventilated areas.
Can an old compressor be used for other purposes?
Yes, many craftsmen use old compressors from refrigerators to create airbrushes, inflate tires, or in aquariums. However, remember that they are not designed for long-term operation without load and can overheat.
Why is the compressor hot to the touch?
During the process of gas compression, the temperature of the refrigerant increases significantly. In addition, heat is generated when the electric motor operates. The compressor housing is not specially insulated so that it releases heat to the environment. Temperatures up to 90°C are considered normal for a working unit.
How many years does a compressor last?
The average service life of a modern compressor is from 10 to 15 years. Inverter models, due to the absence of constant start-stop cycles (peak loads), can last up to 20 years or more. The resource depends on the quality of electricity and operating conditions (room temperature, dust).
Is it possible to replace the compressor yourself?
Theoretically, yes, if you have the skills to solder copper pipes, a vacuum pump and a supply of freon. However, without a license to work with refrigerants and special equipment, it will not be possible to refill the system efficiently. An error will lead to rapid breakdown of the new compressor.
What does the marking on the motor housing mean?
The nameplate indicates the type of refrigerant (R134a, R600a), supply voltage, power, oil type and production date. This data is critical when selecting a replacement. Installing a compressor designed for a different type of freon or oil is unacceptable.
Why may a new compressor not start?
A common reason is the absence or malfunction of the start relay. The problem may also be low voltage in the network. If the new motor hums and does not start, it cannot be kept on for more than 5-10 seconds, so as not to burn the windings.