Starting the compressor is critical the stage of restoring the functionality of the refrigeration unit, which requires strict adherence to technical standards. Asynchronous motor, used in most household models, is not able to start on its own without creating a rotating magnetic field. It is for this purpose that the starting capacitor serves, which shifts the phase for a fraction of a second, allowing the rotor to spin up.
Often, equipment owners are faced with a situation where the old starter has failed, and it is not possible to find an original brand spare part Atlant or Indesit seems possible. In such cases, proper installation of a universal capacitor becomes the only working solution. An error in choosing a capacitance or connection diagram can lead to overheating of the windings and final breakdown of the electric motor.
In this article we will analyze in detail the process of selecting and installing a starting element, eliminating the risk of a short circuit. You will learn how to distinguish the working winding from the starting winding and why the capacitor capacity should exceed 100 uF only for powerful industrial compressors, but for household windings it is much smaller.
The operating principle of a single-phase refrigerator motor
The single-phase asynchronous motor installed in your refrigerator has two main windings on the stator: the main (working) and additional (starting) windings. The working winding occupies two-thirds of the stator slots and creates the main magnetic field necessary to rotate the rotor. The starting winding, made of a thinner wire, is turned on only at the moment of starting.
Without a capacitor, the currents in both windings would be in phase, which would not allow the creation of torque - the motor would simply hum. Capacitorconnected in series with the starting winding, creates a phase shift of the current. This forms an elliptical magnetic field that "spins" the motor shaft to rated speed.
Once the rotor reaches a certain speed (usually about 75% of the rated speed), the starting winding must be disconnected. In classic circuits, this is done by a thermal relay or a centrifugal switch. If the capacitor is left in the circuit, the motor will begin to draw excess current and quickly burn out.
Diagnostics of faults and checking windings
Before proceeding with the installation of a new element, you need to make sure that the element itself is in working order. compressor. Primary diagnostics are carried out using a multimeter switched to resistance measurement mode (Ohm). There are usually three terminals on the motor housing, covered with a plastic block.
You need to find a pair of contacts with the lowest resistance - this will be the starting winding. A pair with a little more resistance is working. The sum of the resistances of these two pairs should be equal to the resistance between the extreme contacts (common wire). If the device shows infinity or zero, the motor is faulty.
⚠️ Attention: If the resistance between any terminal and the compressor housing is less than 2 MΩ, this indicates an insulation breakdown. Operating such a unit is deadly!
It is also worth checking the thermal protection relay. It often fails along with the starter. The relay contacts should "ring" short when cold. If the circuit is broken, the motor will not receive power even if the capacitor is working.
Selecting a suitable capacitor for starting
The key parameter when choosing is the capacitance, measured in microfarads (uF). Domestic refrigerators with a capacity of up to 300 liters usually require capacitors with a capacity of 12 to 50 µF. Using an element with a reduced capacity will not allow the engine to develop the required speed, and an overestimated one will lead to overheating.
The second important parameter is the operating voltage. It should be at least 250 Volts, but experts recommend taking a reserve and installing capacitors at 300-450 Volts. This will ensure stable operation during power surges in the network. The type of capacitor should be exactly starting (Start), and not working (Run), although in emergency cases the use of universal models is allowed.
Overall dimensions also matter. The capacitor must fit into the standard mounting location or into the relay box. Cylindrical models in a plastic case are often used, which are easily secured with a clamp.
| Compressor power | Recommended capacity (uF) | Operating voltage (V) | Dielectric type |
|---|---|---|---|
| Up to 100 W | 12 - 20 | 250 - 300 | Polypropylene |
| 100 - 150 W | 25 - 35 | 300 - 400 | Polypropylene |
| 150 - 200 W | 40 - 50 | 400 - 450 | Metalized |
| More than 200 W | 60 - 80 | 450+ | Oil |
Connection diagram and sequence of actions
The connection process requires care and compliance with safety precautions. Before starting work, be sure to disconnect the refrigerator from the power supply. Remove the rear cover of the unit and get to the compressor.
Remove the old start relay. It is usually held in place by a bracket or latches. Disconnect the wires connecting to the relay contacts. Now your task is to assemble a new chain. One terminal of the capacitor is connected to the starting winding of the engine, the second - to the mains wire (phase) or to the contact where the phase from the relay came.
It is important to ensure reliable contact. Use terminal blocks or quality heat shrink insulation. A simple twist in conditions of vibration of the refrigerator will quickly oxidize and lead to sparking.
☑️ Connection algorithm
Test launch and control of the system operation
After assembling the circuit, it is necessary to carry out a test run. Plug the power cord into a power outlet. If you did everything correctly, the engine should start 1-3 seconds after a characteristic click (if a time relay is used) or immediately, with a slight hum.
Pay attention to the sound of the running motor. A smooth, monotonous hum indicates normal operation. Unusual knocking noises, metallic clanging or intermittent humming indicate problems. If the motor hums but does not start, the capacitor capacity may be too small.
Immediately after starting, check the heating of the capacitor and windings. In the first minutes of operation, they may become slightly warm, but should not be hot. If after 5-10 minutes of operation the temperature of the compressor housing exceeds 60 degrees, the system must be turned off.
⚠️ Attention: The operating time of the starting capacitor is limited! It should be in the chain for no more than 2-3 seconds. If your capacitor remains connected constantly, it may swell or explode.
What to do if the motor hums but does not spin?
This is a classic sign of a “jammed” compressor or a critically low capacity of the starting element. Try to carefully (not with your hands!) rotate the shaft through the coupling, if the design allows, or increase the capacitance of the capacitor by 10-15 uF for a test run.
Typical mistakes in self-repair
One of the most common mistakes is confusion between the working and starting windings. If you apply a starting pulse to the working winding, the motor can start, but will operate with overload and low efficiency. In the long term, this will lead to burning of the insulation.
Ignoring phasing when connecting is also common. Although for a single-phase motor the direction of rotation is usually not critical (in refrigerators it is fixed by design), incorrect connection can disrupt the operation of the thermal relay.
Some craftsmen try to use capacitors from old Soviet technology without checking their residual capacity. Such elements often lose their properties over decades of storage. Before installation, it is advisable to test them with a tester.
It is also dangerous to use capacitors designed for operation in DC circuits. They will instantly fail when connected to a 220V AC network.
Safety measures and final assembly
The final stage is the reliable fixation of all elements. The capacitor should not be loose, as vibration from the compressor can damage its terminals. Secure it with plastic clamps or glue it with heat-resistant sealant to the metal tube (but not to hot areas!).
All live parts must be insulated. Check that the wires do not touch moving parts or hot condenser tubes. Assemble the relay protective casing and install the rear panel of the refrigerator.
Leave the refrigerator turned on for 1-2 hours under supervision. Check if it starts to gain temperature in the chamber. If, after half an hour of operation, cold appears inside and the compressor operates quietly, the repair was successful.
Is it possible to use a working capacitor instead of a starting capacitor?
Technically it is possible, but the starting efficiency will be lower. Run capacitors have a lower capacitance and are not designed for short-term high starting currents. The engine may not develop the required speed.
Why does the new capacitor burn out after a week?
Most likely, the starting relay is faulty, which does not open the circuit after starting. As a result, the capacitor is constantly under voltage, which is unacceptable for starting models.
What voltage margin of the capacitor is needed?
A minimum 20% margin is recommended. For a 220V network, it is better to take 300-400V elements, since at the time of start-up short-term voltage surges above the nominal are possible.
Does polarity affect when connecting a capacitor?
For non-polar capacitors (and these are the ones used in engines), the polarity of the connection does not matter. The main thing is the correct circuit for connecting the windings to the circuit.