Refrigerator motor design: what's inside the compressor and how it works

When the refrigerator suddenly stops freezing, many blame the thermostat or a freon leak. But in 60% of cases, the problem lies precisely in compressor the heart motor of the unit, which pumps refrigerant through the system. At the same time, few people understand how this “black box” under the metal casing works and why it can fail. Understanding the structure of a refrigerator motor is important not only for repairs, but also for proper operation: knowing the weak points, you can extend the life of the equipment for years.

In this article we detailed the design of the compressor - from the stator windings to the piston group valves, we will explain how electricity is converted into mechanical movement, and open the main secret: why modern inverter motors last longer than classic ones, despite a more complex circuit. You will also learn which sounds are considered normal and which signals an imminent breakdown, and how to independently check the performance of the motor without disassembling the refrigerator.

1. Appearance and location of the compressor in the refrigerator

The compressor is a cylindrical or oval block, usually located at the bottom of the refrigerator at the back. It is attached to the frame using spring shock absorbers, which dampen vibrations during operation. The motor is covered with a metal casing on top, and three tubes approach it from below:

• 🔹 Suction tube (thick, often with a filter-drier) - takes freon gas from the evaporator.
• 🔹 Discharge tube (thin, hot to the touch) - supplies compressed refrigerant into the condenser.
• 🔹 Process tube (soldered at the factory) - used for charging freon during repairs.

There is also one on the motor housing starting relay (black box with wires) - it is responsible for starting the engine and protecting against overheating. In modern models (Samsung, LG, Bosch), the relay is often integrated into the control board, and in old refrigerators (Atlant, Biryusa) it is removable.

Important: if the compressor gets very hot (more than 90°C) or makes loud knocking noises, this is not always a sign of a breakdown. For example, in the first 10–15 minutes after switching on, the motor operates at maximum power, and a slight hum with vibration is the norm. But if the noise does not stop after an hour, this is a reason for diagnosis.

2. Compressor structure: what's inside the metal case

Under the casing there is a sealed block, inside of which there are:

1. Electric motor - converts electricity into mechanical movement.
2. Piston group - compresses freon and pumps it through system.
3. Valve mechanism - regulates the direction of movement of the refrigerant.
4. Oil pump - lubricates the rubbing parts.

Let's look at each element in more detail.

A special feature of the compressor is its tightness. The case is laser welded, and it is impossible to disassemble it at home without special equipment. When repairing, technicians usually replace the entire motor rather than repair internal parts.

Why can’t the compressor be disassembled?

A vacuum and a strictly dosed amount of oil are maintained inside the housing. When opened, the seal is broken, air and moisture enter, which leads to oxidation of parts and failure of the motor.

3. Operating principle: how the motor creates cold

The operation of the compressor is based on Carnot cycle a physical process in which the refrigerant (freon) sequentially changes its state: gas → liquid → gas. The motor plays a key role in this cycle:

1. Suction: Low pressure freon gas flows from the evaporator into the compressor cylinder through the inlet valve.
2. Compression: The piston moves upward, compressing freon to high pressure (10–15 atm). The gas temperature rises to 70–90°C.
3. Forcing: Hot freon under pressure is pushed through the outlet valve into the condenser (grid on the back wall of the refrigerator).
4. Cooling: In the condenser, the freon cools down, turning into a liquid state, and then enters the capillary tube, and then into the evaporator, where it again becomes a gas, taking heat from the chamber.

The entire cycle is repeated continuously until the thermostat gives the command to stop. In inverter refrigerators (Samsung Digital Inverter, LG Smart Inverter), the motor does not turn off completely, but smoothly reduces the speed, maintaining a stable temperature without jumps.

4. Types of compressors: which one is in your refrigerator

Modern refrigerators are equipped with three types of motors:

• 🔧 Linear (piston) —the classic version with a reciprocating piston movement. Used in budget models (Atlant, Indesit). Minus: high level of noise (up to 50 dB) and vibrations.
• 🌀 Rotary —piston rotates along an eccentric trajectory. Quieter and more reliable, installed in middle-class refrigerators (Bosch, Electrolux).
• ⚡ Inverter -motor with smooth speed control. Works without stopping, but with variable power. The most durable (resource up to 20 years), but also the most expensive to repair. Used in premium models (Samsung, LG, Liebherr).

How to determine the type of compressor in your refrigerator?

The motor operates almost silently (25–35 dB)|

The body has the inscription "Inverter" or "Digital" Inverter"|

The refrigerator smoothly regulates the temperature without sudden jumps|

The display shows the current compressor power (in %)-->

Inverter motors are sensitive to voltage surges. If there are frequent surges in your network, be sure to connect the refrigerator via stabilizer —this will extend the life of the compressor by 30–40%.

5. Signs of a motor malfunction: when it’s time to sound the alarm

A compressor rarely breaks down suddenly - usually the breakdown is preceded by noticeable symptoms. Pay attention to the following signs:

• ⚠️ The refrigerator does not freeze, but the light inside is on. The motor may hum, but not start (the relay protection is activated).
• ⚠️ The compressor runs without stopping more than 2-3 hours. Reasons: freon leak, clogged capillary tube or thermostat malfunction.
• ⚠️ A knocking or grinding noise is heard inside the motor. This indicates wear of the piston group or breakage of the valves.
• ⚠️ The compressor housing is excessively hot (more than 90°C) or cold (the engine does not start).
• ⚠️ Oil stains appeared on the back wall of the refrigerator is a sign depressurization of the case.

If the motor buzzes, but does not startthe problem may be:

• Start relay (burnt out contacts).
• Stator windings (turn-to-turn short circuit).
• Faulty thermostat (does not give a start signal).

⚠️ Attention: Never try to start the compressor manually by closing the relay contacts. This can lead to firey due to overheating of the windings. For diagnostics, use a multimeter in resistance test mode.

6. How to check the refrigerator compressor yourself

For basic motor diagnostics you will need:

• Multimeter (tester).
• Screwdriver (to access the terminals).
• Pliers (for removing the relay).

Sequence of actions:

1. Disconnect the refrigerator from the network and turn it with the back wall towards you.
2. Remove the starter relay (disconnect the wires, remembering their location, and unscrew the fastenings).
3. Check the resistance of the windings:
   • Measure the resistance between the terminals C-S (working winding) - should be 15-30 Ohms.
   • Measure the resistance between the terminals C-R (start winding) - should be 30-50 Ohms.
   • Measure the resistance between S-R - should be equal to the sum of the two previous values (45-80 Ohms).

Check for breakdown: one multimeter probe on the terminal, the second on the motor housing. Resistance should tend to infinity. If it shows zero, the winding is broken into the housing.

If the resistance of the windings does not meet the standard or there is a breakdown, the compressor must be replaced. In the case of serviceable windings, the problem may lie in relay, thermostat or freon leak.

⚠️ Attention: When checking the compressor do not touch to the terminals with bare hands - the residual voltage in the capacitors can cause an electric shock. Use a tool with insulated handles.

7. Frequent causes of breakdowns and how to avoid them

The average service life of a compressor is 10–15 years, but if used incorrectly, it can fail within 3–5 years. The main causes of breakdowns:

Compressors in refrigerators with a No Frostsystem are especially vulnerable. Due to frequent turning on of the fans, the motor works harder, which accelerates wear. To extend the life of such a refrigerator, defrost it at least once a yeareven if the manufacturer claims that this is not required.

8. Repair or replacement: which is more profitable?

The cost of a new compressor is 30–70% of the price of the refrigerator. For example, a motor for Atlanta will cost 8-12 thousand rubles, and for Samsung RL-60 - 15-20 thousand rubles. Repairs (oil changes, valve cleaning) are possible only in specialized workshops and cost 5–10 thousand rubles, but there is no guarantee of long-term operation.

When it makes sense to repair:

• 🔧 The refrigerator is expensive (premium class) and relatively new (up to 5 years).
• 🔧 Breakdown during the warranty period (compressor replacement is free).
• 🔧 The motor is working, but the problem is in the relay or thermostat (cheap repair).

When is the best time to buy a new refrigerator:

• 🗑️ The equipment is more than 10 years old.
• 🗑️ The cost of repairs exceeds 50% of the price of a new refrigerator.
• 🗑️ The compressor burned out due to a power surge (risk of repeated breakdown).

When choosing new compressor, pay attention to:

• 🔹 Refrigerator model — the motor must be compatible in power and type of freon.
• 🔹 Refrigerant type — old refrigerators work on R-12 or R-134a, new ones - on R-600a (isobutane) or R-134a.
• 🔹 Manufacturer - original compressors (Embraco, Secop, Mitsubishi) last longer than their Chinese counterparts.

⚠️ Attention: When replacing the compressor, be sure to change filter drier and vacuum the system before charging freon. Otherwise, the remaining moisture will lead to repeated failure.

FAQ: Frequently asked questions about the refrigerator compressor

❓ Why is the compressor hot - is it normal?

Yes, heating to 70–90°C is the normal operating mode. The motor compresses freon, which heats up to high temperatures. The only danger is local overheating (for example, one side of the body is hot and the other is cold) - this is a sign of a jammed piston or an interturn short circuit.

❓ Is it possible to turn on the refrigerator after transporting it lying down?

No! After transportation in a horizontal position, oil from the compressor enters the circuit. It is necessary to wait 6–12 hours (depending on the model) for the oil to drain back. Otherwise, the motor will run “dry” and quickly fail.

❓ Why is the new compressor noisier than the old one?

Possible reasons:

• 🔹 Incorrect installation (the compressor touches the housing or tubes).
• 🔹 A non-original motor with a different vibration level is used.
• 🔹 There is air in the system after refilling freon.

If the noise does not disappear after 1-2 days, contact a technician to check the fastenings and pressure in the circuit.

❓ Which compressor is better: inverter or conventional?

Inverter motors are superior to classic ones in three parameters:

1. 🔸 Energy consumption —20–30% lower.
2. 🔸 Noise level - 25-35 dB versus 40-50 dB.
3. 🔸 Durability - resource up to 20 years (for conventional ones - 8-12 years).

But they more expensive to repair and sensitive to power surges. If your network has unstable electricity, it is better to choose a refrigerator with a linear compressor and connect it through a stabilizer.

❓ What to do if the compressor does not start, but the relay clicks?

This is a typical sign turn-to-turn short circuit or jammed piston. Check:

1. Winding resistance with a multimeter (see section 6).
2. Voltage in the socket (should be 220–230 B).
3. Integrity of the starting capacitor (if any).

If the windings are intact and the motor does not spin, most likely the piston is jammed. In this case, the compressor needs to be replaced.