When the refrigerator suddenly stops cooling or makes an unusual humming sound, few owners immediately think about the small cylindrical part in the electrical circuit of the motor. Compressor capacitor - this is a tiny but critical element, without which starting the engine is almost impossible. It is this that creates the necessary starting impulse, allowing the rotor to overcome the inertia of rest and begin rotation.
Modern household refrigerators, such as Indesit, Atlant or LG, use a single-phase network, which by itself is not capable of creating a rotating magnetic field in the motor windings. This is where starting capacitorcomes into play, which shifts the phase of the current in the additional winding, creating the desired torque. Without this device, the motor would only hum quietly, heating up and consuming electricity, but not producing cold.
Understanding how this part works will help you diagnose the problem faster and avoid an expensive call to the repairman if it really is a simple component. In this article we will analyze in detail the physical principle of operation, symptoms of failure and the nuances of selecting analogues for replacement.
The physical principle of operation of the starting device
To understand what is a capacitor for? in the cooling system, you need to turn to the basics of electrical engineering. A single-phase asynchronous motor installed in a compressor has two windings: the main (working) and auxiliary (starting) windings. The working winding creates a pulsating magnetic field, which cannot independently start the rotor. The starting winding, connected through a capacitor, creates a phase shift of the current, which in total gives a rotating magnetic field.
At the moment the refrigerator is turned on, starting capacitor accumulates an electric charge and instantly releases it into the starting winding. This creates a powerful surge of current that “spins” the compressor shaft. Once the engine reaches the required speed (usually 75-80% of rated speed), the start relay opens the circuit, turning off the capacitor and the start winding. Further work occurs only on the main winding.
⚠️ Attention: Some older models of refrigerators can use a two-phase system with a working capacitor, which remains in the circuit constantly. However, 95% of modern household units (for example Beko or Bosch) use short-term starting capacitors.
The key characteristic here is the capacitance, measured in microfarads (μF). If the container is selected incorrectly, the engine will either not start or will overheat, which will drastically reduce its service life. The accuracy of parameter selection is the key to stable operation of the entire system.
Main functions and role in starting the motor
The main task of the element is to ensure a reliable start. At the moment of switching on, the compressor experiences maximum mechanical resistance, since the refrigerant in the system is already under pressure. Starting torquecreated by the condenser must be sufficient to overcome this pressure and the inertia of the piston group.
In addition to creating a starting pulse, the device performs the function of stabilizing the voltage in starting winding. It smoothes out current surges, protecting the thin winding wire from overloads at the critical moment of starting. This is especially important for refrigerators operating under conditions of unstable voltage in the household network.
It is worth noting the difference between starting and operating capacitors. Starters (often labeled as Start) operate for fractions of a second and have a high capacity. Workers (Run) are constantly on, have a smaller capacity and are designed for long-term operation under load. In household refrigerators, starting models are most often found.
- ⚡ Creating a phase shift to form a rotating magnetic field.
- 🚀 Providing high starting torque to overcome freon pressure.
- 🛡️ Protecting the starting winding from current overloads start.
- ⏱️ Short-term operation in tandem with the starting relay (until the speed increases).
If the capacitor loses its capacity, the compressor may hum, but not start. In this case, the thermal protection relay is activated, which opens the circuit to prevent the engine from burning out. The cycles of “attempt to start - shutdown” will be repeated until the fault is eliminated.
Fault symptoms and diagnostics
You can determine what compressor capacitor has failed using a number of characteristic signs. Most often, a breakdown occurs at the moment of switching on: you hear a click of the relay, then a dull hum of the motor, which lasts for several seconds, followed by another click and silence. This is a classic picture of a “failure to start.”
Visual inspection can also give results. If the capacitor body is swollen, blackened, or has traces of electrolyte leaks, its performance is in question. However, often there are no external defects, and accurate diagnosis requires the use of measuring instruments such as a multimeter.
⚠️ Attention: Before any diagnostics, be sure to disconnect the refrigerator from the power supply! Residual charge in the capacitor can cause an unpleasant, although not fatal, electric shock. Close the contacts with a screwdriver with an insulated handle before touching.
Another symptom is compressor overheating. If the motor is running, but the body is hotter than usual, and the cold is not picking up, perhaps the capacitor is “holding” the phase incorrectly, and the motor is operating in an inefficient mode. This leads to increased power consumption.
To check the capacitance, you need a multimeter with a capacitance measurement function. The nominal value is usually indicated on the housing (for example, 30 μF or 45 μF). If the device shows a value significantly lower than the nominal value (for example, 15 μF instead of 30) or a break, the part requires replacement.
Table of common faults
To systematize knowledge about problems associated with starting system, consider the main failure scenarios. This will help you quickly identify the source of the problem in your brand refrigerator Whirlpool, Samsung or any other.
| Symptom | Probable cause | Action |
|---|---|---|
| The compressor hums for 5-10 seconds and turns off | Loss of capacitor capacity or jamming of the motor | Measure the capacitance, check the free play of the shaft |
| A crackling sound is heard, but there is no start | Faulty start relay or open circuit | Check the relay contacts and integrity of the wires |
| Swelling of the capacitor housing | Overheating or power surges in the network | Urgent replacement of the element with a similar one |
| The motor starts, but strongly heats up | Incorrect capacitance (too large or small) | Install the capacitor strictly at its nominal value |
As can be seen from the table, the symptoms may overlap with malfunctions of the compressor itself or the starting relay. Therefore, it is important to carry out due diligence. Sometimes the problem lies not in the capacitor itself, but in the oxidized contacts of the block where it is inserted.
Is it possible to start a refrigerator without a capacitor?
Theoretically, if you manually turn the shaft of a running compressor (which is dangerous and difficult), it can continue to work. But it is impossible to start it statically without a starting device - it will only hum and burn out.
How to choose the right analogue for replacement
When searching for a replacement, the most detailed parameter is the capacitance (in microfarads, µF/µF). It must match the original. A slight deviation of ±5-10% is allowed, but it is better to look for an exact match. For example, if standing 30 uF, you cannot set 20 or 50 uF.
The second important parameter is the operating voltage. It must be equal to or higher than the original. Standard values for refrigerators are 250V, 300V, 450V. If you put a capacitor at 250V instead of 450V, it will quickly break down. If it is 450V instead of 250V, it will work fine, it will just take up a little more space.
Also consider the overall dimensions. The condenser must physically fit into the compressor niche and not interfere with the installation of the casing. Sometimes more capacious analogues have a larger diameter or height. In such cases, you can be smart and fix the part nearby, lengthening the wires if the design allows it.
- 📏 Capacity: strictly observe the nominal value (for example, 30 uF).
- ⚡ Voltage: choose a value equal to or higher (minimum 250-300V).
- 🌡️ Temperature conditions: frost-resistant models are important for refrigerators.
- 🔌 Connection type: check the location of the terminals (2 or 3 pins).
Pay attention to the temperature range. Since the condenser is located in the compressor area where the temperature can rise, it is advisable to select products with a wide range of operating temperatures (for example, from -40°C to +85°C). This will ensure stable operation in winter in an unheated room.
☑️ Check before purchase
Instructions for self-replacement
Replacement start capacitor is one of the simplest operations in refrigerator repair, accessible even to a beginner. The main thing is to follow safety precautions and sequence of actions. All you need is a new part, a screwdriver and maybe some pliers.
First unplug the refrigerator and remove the rear protective cover at the bottom of the case. You will have access to the compressor. Find the black box (start relay) and the cylinder attached to it - this is our hero. Carefully remove the retaining bracket or clamp.
⚠️ Attention: Do not jerk the wires sharply. Wiring in older refrigerators can be dry and brittle. All movements must be smooth so as not to break the contacts.
Disconnect the old capacitor. Depending on the model, it may be removed together with the relay block or have separate wires. Take a photo of the connection diagram before disconnecting so as not to mix up the wires when installing a new element. Install the new capacitor, securely fasten it and assemble the casing.
After assembly, turn on the refrigerator. The first minutes of work should pass without any extraneous sounds. The compressor should start with a characteristic hum, which after 1-2 seconds will turn into a smooth hum. If the startup was successful, you can consider the repair complete.
Frequently asked questions (FAQ)
Can a capacitor of higher capacity be used?
Using an element with a capacitance significantly higher than the nominal value (more than 20%) will lead to overheating of the starting winding and may burn the compressor. If the difference is within 5-10% (for example, 30 µF instead of 28 µF), this is acceptable, but undesirable.
Why did the new capacitor explode immediately after switching on?
Most likely, the operating voltage was exceeded or the polarity was reversed (if the capacitor is electrolytic, although in refrigerators they are often non-polar). Also, the reason may be a malfunction of the starting relay itself, which does not turn off the winding in time.
Where to find the markings on the capacitor?
Usually the parameters (capacitance, voltage, tolerance) are printed directly on the side surface of the cylindrical body. Look for numbers marked µF or mF and V. If the inscription is erased, look for the model of the refrigerator in the documentation.
How much does it cost to replace a capacitor in the service?
The cost consists of the price of the part (usually 300-800 rubles) and the work of the technician. In service centers, the price for visiting and replacing can vary from 1,500 to 3,000 rubles, so independent replacement is economically feasible.