When the refrigerator suddenly stops freezing or starts making strange sounds, the first thing that comes to the owner’s mind is a motor breakdown. Indeed, compressor is the heart of any refrigeration system, and the safety of products directly depends on its serviceability. Understanding what is hidden inside the metal casing helps not only to diagnose the problem, but also to avoid unnecessary expenses on repairs or replacement of components.
Inside the sealed housing there is a complex mechanism that operates in extreme conditions. There is no place for accidents: every detail, from the piston to the winding electric motorperforms a strictly defined function. In this article we will look inside this “black box”, analyze the principle of operation of different types of compressors and find out why some of them work silently, while others hum like a tractor.
Many people confuse the concepts of motor and compressor, considering them one whole, which is not without meaning, since in household refrigerators they are combined into a single unit. However, technically electric motor it only sets in motion the piston group, which compresses the refrigerant. The difference in the design of these components is colossal, and it is this that determines the service life of all equipment.
Principal diagram of the compressor operation
The main task of the compressor is to create a pressure difference in the system, forcing the refrigerant to circulate throughout the circuit. Located inside a sealed flask filled with an inert gas or under vacuum, electric motor. When voltage is applied, its rotor begins to rotate, transmitting torque to the crankshaft of the crank mechanism.
This shaft, in turn, drives the pistons, which drive freon gas from the evaporator into the condenser. It is important to note that the compression process is accompanied by significant heat release, so the engine housing is always hot. Modern models use an oil cooling system, which is sprayed inside the housing and lubricates the rubbing parts.
The motor design is usually asynchronous, with a squirrel-cage rotor. The stator is fixedly mounted on springs or rubber shock absorbers to dampen vibrations. A rotor mounted on a shaft rotates inside the stator, creating the magnetic field necessary for operation. The tightness of the housing is critical: getting moisture or air inside will lead to rapid corrosion and failure of the windings windings.
⚠️ Attention: Opening the sealed compressor casing at home is strictly prohibited. There may be gas under pressure inside, and a violation of the seal makes further operation of the unit impossible without complex factory soldering and vacuuming.
Oil circulation inside the housing is a separate engineering challenge. Oil should not enter the cooling circuit in large quantities, as this reduces the efficiency of heat transfer. For this, the system is equipped with oil separators and special channels that return the lubricant back to the crankcase.
Internal structure: piston and inverter systems
Traditionally, piston compressors were used in refrigerators. Inside such a unit, the piston moves back and forth. When the piston lowers, the pressure in the suction chamber drops, and a new portion of refrigerant is sucked in through the inlet valve. During the upward stroke, the gas is compressed and pushed through the discharge valve into the condenser.
Unlike them, inverter engines operate on a different principle. There is no need to constantly turn the motor on and off. The rotor of such an engine rotates continuously, changing speed depending on the need for cold. This is achieved by changing the frequency of the current supplied to the stator windings.
- 🔹 Piston systems are reliable, but create vibration and noise when starting.
- 🔹 Inverter motors operate smoothly, saving up to 30% electricity.
- 🔹 Rotary compressors (rarely) use a rotating rotor with plates, which makes them more compact.
Inside the inverter compressor there is also a powerful magnet installed on the rotor, which makes the design sensitive to power surges in the network. An electronic control unit, built into the housing or remotely controlled, controls each turn of the stator spiral, providing precise power control.
It is also worth mentioning linear compressors, which are often confused with inverter compressors. In them, the piston moves linearly, without rotational movements, due to electromagnetic forces. The absence of a crank mechanism reduces the number of rubbing parts, which theoretically increases the service life. However, in practice, such systems require very high-quality coolant and stable voltage.
Electric motor starting and protection system
Starting an asynchronous motor requires the creation of an initial torque. For this purpose, in older and budget models, a start-up relay is used. It connects the starting winding only at the moment of start, and then opens the circuit. If the engine does not start within a few seconds, the relay operates as overload protection.
In modern models, this function is taken over by electronics. Inside the housing or in the external control unit there are thermistors and current sensors that monitor the condition of the windings. If the rotor overheats or jams, the power is turned off instantly, preventing combustion of insulation.
The thermal relay, often installed directly on the compressor housing, reacts to temperature. If the motor heats up above a critical point (usually about 120-130°C), the bimetallic strip opens the contacts. After cooling, the contacts close and the cycle repeats. If you hear frequent clicks, but the refrigerator does not freeze, the problem is in this circuit.
☑️ Diagnosis of startup problems
The capacitor, if present in the circuit, serves to create a phase shift of currents in the starting winding. Failure of this small component often results in the motor humming without turning the shaft. Replacing a capacitor is one of the simplest and cheapest procedures in repair refrigerators.
Typical malfunctions of internal components
The most common problem is an interturn short circuit in the stator windings. This occurs due to overheating or aging of the varnish coating of the wires. As a result, the motor begins to consume more current, overheat, and eventually burns out. This can be determined by the black color of the oil and the burning smell when opened (which only a specialist can do).
The second common reason is mechanical wear of the piston-cylinder pair or shaft bearings. The gaps increase, compression drops, and the refrigerator stops reaching the desired temperature, although the motor runs continuously. Metal shavings entering the oil speed up this process, acting as an abrasive.
| Symptom | Probable cause inside the motor | Consequences |
|---|---|---|
| Humming, but does not start | Jagging of the piston group | Burning of windings |
| Strong vibration | Destruction of suspension shock absorbers | Breakage of tubes inside |
| The housing is heating up | Lack of oil or blockage | Thermal destruction of insulation |
| Relay clicks | Malfunction of the starting winding | Start failure |
Clogged capillary tube or filter drier also affects engine operation. The compressor has to work “in vacuum” or in overload mode, trying to push freon through the plug. This is not an internal failure of the motor, but leads to its premature wear.
Is it possible to restore a jammed compressor?
There is a method of “wedging” by applying increased voltage or mechanical shock, but its effectiveness is low (about 10%), and the risk of finally finishing off the unit is very high. Professionals rarely undertake this, preferring a replacement.
Oil and refrigerant: the environment of the engine
There is always a special refrigeration oil inside the compressor. It should not freeze at low temperatures and lose viscosity at high temperatures. Depending on the type of freon (R134a, R600a, R12), different brands of oils are used: mineral, alkylbenzene or polyester (POE).
The peculiarity of polyester oils is their high hygroscopicity - they actively absorb moisture from the air. Therefore, during repairs, you cannot leave the system open for more than 15-20 minutes. Moisture getting inside will lead to the formation of acids that corrode windings of the engine and metal parts.
- 🔹 Mineral oils are compatible with freon R12 and R134a.
- 🔹 Synthetic oils (POE) are required for freon R600a (isobutane).
- 🔹 Mixing different types of oils is prohibited - sediment will form.
The amount of oil is strictly regulated by the manufacturer. A lack of lubrication leads to dry friction and scuffing, and an excess leads to water hammer and a drop in performance, since liquid oil, once in the cylinder, is not compressed, unlike gas.
⚠️ Attention: When replacing a compressor with one operating with freon R600a (isobutane), special fire safety must be observed. This gas is explosive. All work with an open flame (soldering) is carried out only after complete gas evacuation and purging of the system.
Diagnostics and serviceability check
Before removing the engine, it is necessary to carry out initial diagnostics. First of all, the resistance of the windings is checked using a multimeter. Normal values vary between 10-30 Ohms for the working winding and 20-50 Ohms for the starting winding (depending on the model). If the device shows zero - a short circuit, if infinity - an open circuit.
It is also important to check the resistance between the housing and the winding terminals. It should tend to infinity. Any “leak” on the housing indicates a breakdown of the insulation, which is dangerous for the user’s life and requires immediate replacement of the unit.
Another method is to check for “wedging”. If the windings are intact, but the motor does not start, you can try to apply voltage directly (for a short time!), bypassing the relay. If the shaft jerks and the hum changes, there may be a problem with the starter. If the motor hums and heats up, but the shaft is standing, there is a mechanical defect inside.
Resource and durability of various types of motors
The average service life of a modern compressor is 10-15 years. However, inverter models often have a declared resource of up to 20 years or more. This is due to the absence of start-stop cycles, which are the most stressful for mechanics and electrics.
Durability is affected not only by the build quality, but also by operating conditions. Frequent voltage drops in the network are detrimental to the electronics of inverters, and contamination of the capacitor at the back of the refrigerator causes the motor to work with overload, shortening its life.
Manufacturers are constantly improving technology. The use of more durable alloys, improved cylinder geometry and high-quality bearings allow modern units operate almost silently. However, the more complex the device, the more expensive it is to repair in the event of a breakdown.
Why may a new compressor fail to start?
A common reason is incorrect installation of the starting relay or the use of a relay from a different model. It is also possible that debris gets into the system during soldering, which blocks the movement of freon and creates back pressure that the motor cannot overcome.
Can a compressor from a refrigerator be used for other purposes?
Yes, they are often used to create homemade compressors for airbrushing or inflating tires. However, you need to remember that such motors are not designed for constant operation under load without cooling and may require upgrading the lubrication system.
What does the marking on the compressor nameplate mean?
It indicates the type of refrigerant (for example, R134a), supply voltage, power, type of oil and its quantity. This data is critically important when selecting a replacement, since installing an unsuitable unit will lead to rapid breakdown.
In conclusion, the refrigerator engine is a high-precision mechanism where every micron of clearance matters. Understanding its internal structure helps you treat technology more carefully and notice signs of future problems in time. Regular cleaning of the condenser and protection against power surges are the best ways to extend the life of the “heart” of your refrigerator.