Sudden stop of the refrigeration unit - It’s always stressful because food supplies are at risk. Most often, the cause of a breakdown is the failure of the compressor or its starting equipment. Understanding exactly how it is connected refrigerator motorallows not only to diagnose a malfunction, but also, in many cases, to extend the life of household appliances without calling a technician.
The process of replacing or initially installing a motor requires not so much high qualifications as attentiveness, accuracy and strict adherence to electrical safety rules. Any error when connecting wires can lead to a short circuit or final burnout of an expensive unit. Therefore, before taking up the tools, it is necessary to carefully study the design of the unit and prepare the workplace.
In this article we will analyze in detail the electrical circuit of a single-phase asynchronous motor, consider the features of connecting the starting and running capacitors, and also analyze the nuances of installing a protective relay. You will learn how to correctly determine the terminals of the windings and why the color of the wires does not always correspond to the factory diagram.
Design and principle of operation of the compressor
The heart of any refrigeration system is compressor, which is a sealed electromechanical unit. Inside the metal casing there is an electric motor and a compressor part, the shafts of which are on the same axis. The engine is immersed in oil, which ensures lubrication of rubbing parts and heat removal during operation.
The electrical part of the motor consists of two main stator windings: working (main) and starting. The working winding occupies two-thirds of the stator slots and has a thicker wire, ensuring constant rotation of the rotor. The starting winding has a smaller wire cross-section and is turned on only at the time of start-up, creating the necessary torque.
A special start-up relay is used to control these windings. It is this small block that takes the brunt of the current load at the moment of start. Inside the relay there are contacts that are opened by the thermal expansion of a bimetallic plate or an electromagnetic coil, which protects the engine from overloads.
⚠️ Attention: The compressor housing is under high pressure and filled with refrigerant. It is strictly forbidden to open the sealed casing or try to drill holes in the tubes unless you plan to completely recharge the system using professional equipment.
Modern models are often equipped with inverter motors, the connection diagram of which is radically different from the classic ones. In such systems, between the network and the motor there is an electronic control unit that converts alternating current into direct current and back with a variable frequency.
Necessary tools and safety measures
Before starting any work with electrical equipment, it is necessary to ensure that the device is completely de-energized. Unplug the refrigerator from the outlet and make sure that there is no access to the electrical outlet. Working with a voltage of 220 Volts requires increased concentration and a working tool.
To carry out diagnostics and connections, you will need a standard home repair kit. The main device will be a multimeter (tester), which allows you to check the integrity of the windings and the absence of breakdown on the housing. Without this device, starting work is pointless and dangerous.
You will also need the following tools and materials:
- 🔧 A set of screwdrivers (phillips and flat) for removing casings and terminal boxes.
- 🔪 Side cutters or wire cutters for cutting and stripping wires insulation.
- 🧤 Dielectric gloves to protect against accidental electric shock.
- 📏 Insulating tape or heat shrink tubing to insulate connections.
If you are replacing the entire compressor, make sure that the new unit fully matches the technical specifications of the old one. The power, refrigerant type and overall dimensions must match. Using an unsuitable motor will result in inefficient operation of the refrigerator or rapid breakdown.
Work in a well-lit area. Poor lighting can cause you to mix up wire colors or miss a microcrack in the insulation. Prepare a clean surface so as not to lose small screws and relay mounting parts.
Pin markings and connection diagram
The most difficult step for a beginner is the correct identification of the winding pins. On old Soviet refrigerators, the terminals were often marked with letters, while modern Asian and European models use numerical or color coding. An error in the connection will result in the motor humming without starting or the windings burning out.
Usually there are three contacts on the compressor block. Two of them belong to the working winding, and one to the starting winding. To determine them, you need to “ring” the windings with a multimeter in resistance measurement mode. The resistance of the starting winding is always higher than the working winding, since it is wound with a thinner wire.
Consider the standard table of pin correspondence for different types of compressors:
>Green/Yellow
| Marking type | Common wire (C) | Working winding (R) | Starting winding (S) |
|---|---|---|---|
| European | C (Common) | R (Run) | S (Start) |
| Asian/RF | General | Working | Trigger |
| Color (often) | Red/Brown | Blue/Black | |
| Resistance | Sum of R and S | Lesser (20-50 Ohms) | More (30-100 Ohms) |
When you make a call, you will find that between the two contacts the resistance is greatest - these are the ends of the starting and working windings. The third contact, which gives the least resistance with each of them separately, is the common conclusion. It is to this that phase or zero is supplied, depending on the circuit.
It is important to understand that the color of the wires coming from the relay does not always match the colors of the wires on the compressor itself, especially if the equipment has already been repaired before. Always rely on measurements with a multimeter, and not on a visual assessment.
Connecting the starting and protective relay
The starting protection relay is a key element that ensures engine starting and protection. It is put directly on the compressor terminals. Structurally, the relay consists of a starting coil, contacts and a thermal release. When voltage is applied, current passes through the starting winding, the rotor begins to rotate, and the contacts open.
The relay installation process requires care. It should fit snugly on the terminals, but without excessive force that could break the ceramic insulators or the terminals themselves. The orientation of the relay is strictly defined: usually the arrow or inscription "UP" should face up.
The network connection diagram is as follows:
- 🔌 Phase wire from the network it goes to the input of the thermal relay, and then to the common terminal of the compressor.
- ⚡ Neutral (zero) connects directly to the working winding.
- 🔄 Starting winding is powered through the starting relay contacts parallel to the working one.
If in If your model uses capacitor starting, then the capacitor is connected in series with the starting winding. Its capacity must strictly comply with the manufacturer's requirements. Replacing the capacitor with an analogue with other parameters is unacceptable.
The thermal relay operates on the principle of metal expansion. If the current in the windings exceeds the norm (for example, when the piston group is jammed), the bimetallic plate bends and opens the circuit. After cooling, the contacts close again, trying to start the motor again.
☑️ Check before turning on
Diagnostics of startup faults
After connecting the refrigerator motor, the moment of truth comes - the first start. Plug in the unit and listen carefully to the sounds coming from the compressor. The nature of the sound and the behavior of the ammeter needle (if any) will say a lot.
If you hear a loud hum, but the engine does not start, and after a few seconds there is a click and silence, this is a sign of a faulty start relay or a jammed compressor. In this case, you must immediately disconnect the device from the network.
Possible scenarios for system behavior:
- 🔇 Complete silence: No power to the relay, the thermal relay is burned out or the circuit inside the windings is broken.
- 🔊 Humming and clicking: The motor is trying to start, but there is not enough starting torque (problem with a relay or capacitor).
- 🌡️ Case heating: The compressor works, but gets very hot, perhaps the ventilation is broken or the valve is faulty.
A common problem is the “sticking” of the piston group after a long period of inactivity. In such cases, sometimes a short-term supply of voltage to the starting winding, bypassing the relay, helps, but this method requires experience and is dangerous for inexperienced users.
⚠️ Attention: If, when turned on, the circuit breaker in the panel is knocked out or the fuse blows, this indicates a short circuit in the windings or an insulation breakdown on the housing. It is prohibited to operate such a refrigerator!
To accurately diagnose starting currents, use current clamps. The starting current can be 5-7 times the rated operating current, but it lasts a fraction of a second. If the current is constantly high, the motor is faulty.
Replacing the compressor: installation nuances
If the diagnostics showed that the motor itself is faulty (interturn short circuit or break), its replacement is required. This is a more complex procedure that requires working with the refrigeration circuit. You will need a torch, solder and a vacuum pump.
The first step is to bleed off the refrigerant. Open tubes only in a well-ventilated area. Then the old compressor is dismantled: the suction and discharge tubes are cut, the fastening legs are unscrewed.
Installation of a new unit includes the following steps:
- 🔥 Soldering pipes: connecting copper tubes using nitrogen purge to prevent oxidation inside the system.
- 💨 Evacuation: removing air and moisture from the circuit before charging with freon.
- ❄️ Filling: adding a strictly defined amount of refrigerant by scale.
The electrical connection of the new compressor is made according to the same scheme as the old one, but be sure to install a new start-protection relay. The old relay could not work correctly, which led to the breakdown of the motor, and its reuse is risky.
Is it possible to use a compressor from another brand?
Yes, you can, if the power, type of refrigerant and overall dimensions of the seats match. However, it is better to look for the original model or its direct analogue by catalog number.
After assembling the system and electrical connection, check the tightness of the connections with a soap solution. Bubbles will indicate a leak that must be eliminated before refueling the refrigerator.
Frequently asked questions (FAQ)
Is it possible to connect a three-phase motor to a single-phase refrigerator network?
Theoretically, this is possible using capacitors, but for a domestic refrigerator this is inappropriate. Three-phase motors have different torque characteristics and require alteration of the winding connection diagram (star/delta), which is impossible to do in a sealed casing.
Why does the starting relay heat up after replacement?
Heating of the relay may indicate poor contact in the terminals, wear of the contacts inside the relay itself, or incorrect selection of the model. Also, the reason may be an increased current consumption by the compressor itself due to wear of the mechanical part.
How to determine whether the motor winding has burned out?
If there is an inter-turn short circuit, the winding resistance will be significantly lower than normal, and if there is a break, the multimeter will show infinity. Also, a sign of a burnt winding is a characteristic burning smell and a black coating on the terminals.
Is it necessary to change the filter drier when replacing the compressor?
Yes, this is a mandatory requirement. The old filter has accumulated moisture and dirt, which will quickly damage the new compressor. If the circuit is depressurized, the filter-drier must always be replaced.