When the refrigerator stops humming or, conversely, begins to make unnatural sounds, the first thing that comes to mind is a problem in the “heart” of the unit. Many users mistakenly call the entire compressor assembly a motor, although technically it is only part of a complex system. Understanding what is in the refrigerator enginehelps not only in diagnosing malfunctions, but also in the correct selection of spare parts for repair.
Inside the sealed casing is hidden a complex mechanism operating under high pressure. This is where electrical energy is converted into mechanical energy, forcing the refrigerant to circulate through the system and remove heat from the chambers. Modern models may differ significantly from equipment released twenty years ago, but the basic principles of operation remain unchanged. We will analyze the internal structure in detail so that you can imagine what processes are happening behind the metal wall.
It is important to immediately note that opening the compressor yourself without special equipment is impossible and dangerous. However, knowledge of the design will allow you to correctly describe the symptoms of a breakdown to a technician or understand whether it is worth undertaking repairs at all. Sealed units cannot be restored at home, but diagnostics of external elements is available to everyone.
Main components of the compressor unit
What is in In everyday life they call it an engine; it would be more correct to call it compressor. This is a sealed metal cylinder, inside of which there is an electric motor and the compression mechanism itself. All these parts are immersed in a special oil, which provides lubrication of the rubbing pairs and cooling of the windings. The housing is usually made of steel and welded at the factory to prevent freon leakage.
Inside the casing there is a stator and rotor of the electric motor. The stator is rigidly mounted on the inner surface of the casing or on special shock absorbers, and the rotor is mounted on a shaft, which drives the piston group. Crank mechanism converts the rotational movement of the shaft into the translational movement of the piston. It is the piston, moving up and down, that compresses the gaseous refrigerant, increasing its pressure and temperature.
Valves are used to take in and discharge gas. They are thin metal plates that open and close under the influence of pressure differences. Suction valve passes gas from the evaporator, and the discharge one sends compressed freon to the condenser. Malfunction of these microscopic parts often leads to loss of performance.
⚠️ Attention: A vacuum and high pressure are created inside the compressor at the same time. Under no circumstances should you try to cut the housing or break its seal - this may result in hot oil splashing and the release of toxic substances.
The suspension system should also be mentioned. The motor-compressor is mounted inside the casing on springs. This is necessary to dampen vibrations that occur during operation. If the springs break or jump off, the refrigerator begins to vibrate and rattle strongly, although the compression mechanism itself may be working properly.
Electrical part: windings and starting device
The electric motor located inside the casing is asynchronous. It has two main windings: working and starting. The working winding creates the magnetic field necessary to rotate the rotor during normal operation. Starting winding It is turned on only for a short time at the time of start-up to create an initial torque and spin the shaft.
The switching of the windings is controlled using a starting relay. Older models used posistor or electromagnetic relays, while newer ones often use electronic circuits. If the starting winding burns out or the relay sticks, you hear a characteristic click, followed by a hum, but the compressor does not start.
The terminals of the windings are approached by contacts brought out through a sealed block. It is to them that the wiring from the thermostat or electronic control module is connected. Overheating of the windings is a common cause of failure, so many modern models are equipped with an internal thermal relay that opens the circuit when the temperature rises critically.
- 🔌 Working winding —has greater resistance and a greater number of turns of thin wire, it works constantly.
- ⚡ Starting winding —has less resistance, consists of a thicker wire, turns on for a short time.
- 🛡️ Thermal relay —protects the engine from overheating, opening the circuit at a temperature of about 130-140°C.
Diagnostics of the electrical part is possible without opening the casing. By testing the resistance between the contacts on the external block with a multimeter, you can determine the integrity of the windings and the presence of a breakdown to the housing. Normal resistance is usually from 10 to 30 Ohms, depending on the power of the motor.
Types of compressors: piston and inverter
Traditionally, piston compressors were used in refrigerators. In them, gas compression occurs due to the movement of the piston in the cylinder. Such devices are reliable, but have a number of disadvantages: high noise levels, vibration and stepwise power adjustment. The motor in such units operates on the “on-off” principle, which creates peak loads on the network and mechanics.
Modern models are increasingly equipped with inverter compressors. They do not have a strict connection between the shaft rotation speed and the frequency of the current in the network. The electronic control unit smoothly changes the engine rotation speed, maintaining the set temperature without stopping. This saves energy and reduces wear of parts.
Inside the inverter motor there are magnets and windings operating on the principle of a linear drive or with frequency conversion. The absence of rubbing pairs in the traditional sense (in linear compressors the piston moves back and forth under the influence of an electromagnetic field) makes them extremely quiet. However, the electronics of such devices are sensitive to voltage surges.
| Characteristics | Piston compressor | Inverter compressor |
|---|---|---|
| Operating principle | On/Off | Smooth speed control |
| Noise level | Medium/High | Low |
| Energy consumption | High | Low (class A++ and higher) |
| Service life | 7-10 years | 10-15 years or more |
Choice between types compressors often becomes a budget issue. Inverter models are more expensive to purchase and repair, but pay for themselves due to electricity savings and durability. Linear inverter systems used in the premium segment combine the advantages of both types.
Why can an inverter compressor hum?
Inverter motors can produce a high-frequency hum or whistle that is not heard in conventional compressors. This is due to the operation of the frequency converter and magnetostrictive effects in the metal. If the sound is not accompanied by vibration of the housing, this is considered normal.
The role of oil and refrigerant in the system
Inside the refrigerator engine there are not only mechanics, but also working fluids. Special compressor oil necessary for lubrication of rubbing parts: piston, cylinder, shaft bearings. It must have the following properties: not to freeze at low evaporator temperatures and not to lose viscosity when heated.
The oil circulates along with the refrigerant. A small portion of the oil is always carried away by the gas flow into the system, but special oil separators and design features return it back to the compressor crankcase. If the oil becomes too low, dry friction begins, overheating and seizing. If there is too much, the efficiency of heat transfer decreases.
The refrigerant (freon) also passes through the compressor cavity. As it is sucked through the suction tube, it cools the windings of the electric motor. Therefore, it is so important that the refrigerator operates at normal temperature conditions. Overheating or operation in a too hot room can lead to oil degradation and the formation of acids that corrode the insulation of the windings.
⚠️ Attention: When replacing the compressor, you must strictly observe the type and amount of oil being poured. Using universal oils or oils for other types of freons (for example, mineral instead of synthetic POE) will lead to rapid failure of the new part.
Oil life is limited. Over time, it oxidizes and wear products and moisture accumulate in it. In a sealed circuit, this process is slow, but with frequent switching on/off or overheating, the lubricant life is used up faster.
Cooling system and heat sink
Despite the fact that the refrigerator cools food, its engine gets very hot during operation. The main source of heat is gas compression and electrical resistance of the windings. Cooling occurs due to the natural convection of air around the casing and the transfer of heat to the refrigerant, which is sucked inside.
The compressor housing is often covered with black enamel, which improves heat transfer. Some powerful models may have an additional fan installed to blow the motor, although this is rare in domestic refrigerators. It is important to ensure free air circulation around the back wall of the refrigerator.
If the space behind the refrigerator is filled with things or the equipment is pushed close to the wall, the heat dissipation is disrupted. Casing temperature it can rise to critical values, which will trigger the thermal relay and stop the motor. Regular overheating reduces the service life of winding insulation.
☑️ Checking cooling conditions
Particular attention should be paid to the temperature in the room where the refrigerator is located. If the kitchen is hotter than +30°C, the engine efficiency decreases and wear increases. In such conditions, the engine is forced to work longer and more intensely in order to maintain cold in the chambers.
Diagnostics of engine malfunctions
You can understand what is happening inside the engine by external signs. The most common symptom is the compressor hums but does not start. This may indicate a mechanical jam or a faulty start relay. If the motor starts, but after a few seconds it clicks and turns off, the thermal protection is triggered.
Extraneous sounds, such as metallic knocking or grinding, often indicate destruction of the bearings, valves or piston group. In this case, active wear occurs inside the engine, and parts fall into the gaps. Double hum may indicate problems with the motor suspension inside the casing.
Checking the resistance of the windings is the first diagnostic step. To do this, you need to remove the start relay and get to the contacts. Normal multimeter readings depend on the model, but usually the resistance between the working and starting contacts is equal to the sum of the resistances relative to the common contact.
- 🔍 Visual inspection - check for dents, rust, traces of oil (indicates depressurization).
- 🌡️ Temperature control - the casing should be hot, but non-burning (norm up to 90°C).
- 🔌 Current measurement —the starting current can be 3-5 times higher than the operating current, which must be taken into account when diagnosing.
If the diagnostics show a break in the windings or mechanical knock inside the hermetic unit, repair is impossible. A complete replacement of the compressor unit is required. Attempts to disassemble and sort out such a unit at home do not make sense due to the need for precise alignment and evacuation.
Frequently asked questions (FAQ)
Is it possible to lubricate the refrigerator motor if it starts to make noise?
No, it is not possible. The engine is housed in a sealed welded casing. Any attempt to drill a hole for lubrication will break the seal, moisture and oxygen will get inside, which will lead to rapid corrosion and failure. The noise indicates mechanical wear, and only replacing the unit will help.
Why is the refrigerator motor hot to the touch?
This is normal. During the compression of freon and the operation of the electric motor, a lot of heat is released. The temperature of the compressor casing can reach 70-90 degrees Celsius. The main thing is that the thermal relay is triggered when overheated and there is no burning smell.
How much does a refrigerator engine weigh?
The weight of the compressor varies depending on the power and model. Typically, household compressors weigh between 8 and 12 kilograms. Inverter models can be lighter or heavier depending on the design, but on average the weight remains within these limits.
Is it possible to use a compressor from a refrigerator for other purposes?
Yes, old serviceable compressors are often used to create homemade compressors for airbrushing, inflating tires or pneumatic tools. However, you need to remember that they are not designed to create high pressure in the receiver and require proper organization of oil separation.
What to do if the refrigerator engine burns out?
You need to call a technician for an accurate diagnosis. If combustion of the windings or knocking inside is confirmed, the compressor will need to be replaced. Repairing an old one by rewinding is not economically feasible and is technically difficult due to the tightness of the case.