The question of how to start a refrigerator without a starting winding often arises among amateur craftsmen who are faced with a burnt-out wire inside the stator electric motor. Intuitively, it seems that if the engine is powerful, then one working winding should be enough to rotate the rotor, especially if it is helped a little by hand. However, the physics of operation of asynchronous motors used in household appliances dictates its own strict conditions, ignoring which leads to fatal consequences for the compressor.
A standard single-phase refrigerator motor Indesit or Atlant is designed so that the starting winding creates the necessary phase shift for the occurrence of rotating magnetic field. Without this shift, the rotor only hums and vibrates in place, without doing any useful work. Trying to start the unit by excluding this element from the circuit is tantamount to trying to drive a car with the front wheels locked - energy will be wasted, turning into heat and destroying the insulation.
In this material we will analyze in detail why starting winding is critically important, what theoretical schemes exist to bypass the standard starting system and why in practice they almost always lead to the need for replacement motor-compressor. We will consider the electrical characteristics, thermal conditions and the real possibility of operating equipment in emergency mode.
The principle of operation of a single-phase asynchronous motor
To understand the impossibility of full operation without a starting circuit, you need to turn to the theory of electrical engineering. The stator of a refrigeration compressor has two windings: the main (working) and auxiliary (starting) windings. The working winding occupies most of the stator slots and creates the main magnetic field, but it generates only a pulsating field, not a rotating one. Rotor in such a field it cannot start moving on its own, it needs an initial impulse.
The starting winding is connected in parallel to the working winding, but through a phase-shifting element - a capacitor or active resistance. It is the presence of two windings, shifted in space by 90 electrical degrees and powered by currents with different phases, that creates the effect of a rotating magnetic field. This process causes the rotor to gain speed. As soon as the rotation speed reaches 75% of the nominal, the starting winding in classical circuits is turned off by the relay.
If you try to apply voltage only to the working winding, the engine will remain in a static position. The current in the winding will increase to maximum values (short circuit current), since there is no self-induction emf that occurs during rotation. This leads to instant heating and thermal breakdown of the insulation. Without creating a rotating torque, the rotor will not move from a dead point, no matter how much voltage you apply.
⚠️ Attention: An attempt to apply voltage to the working winding for a long time without rotating the rotor is guaranteed to lead to an interturn short circuit and complete burnout stator in a few seconds.
There are modifications of motors where the starting winding is not turned off and runs constantly (capacitor motors), but this is rare in domestic refrigerators. The launch mode is used there. Even if the rotor is spun manually, the moment of inertia and the load of the piston group of the refrigerator are too large for one winding to maintain rotation under freon pressure.
Theoretical starting schemes and their implementation
Considering the question of whether it is possible to start a refrigerator without a standard starting winding, theorists offer several circuit solutions. The first involves the use of an external large capacitor, which artificially creates a phase shift. However, choosing a capacity for a powerful compressor is extremely difficult, and the risk of an electrolyte explosion is high.
The second option is to use a frequency converter (inverter). This device converts single-phase current into three-phase or changes frequency, creating the necessary rotating field without the participation of the second stator winding. But the cost of such equipment often exceeds the price of a new compressor, and the dimensions do not allow them to be built into the body of an old refrigerator.
- 🔌 Connection through a powerful capacitor: requires accurate calculation of capacitance and voltage, often leads to overheating.
- ⚙️ Using a frequency drive: effective, but not economically feasible for old equipment.
- 🔧 Mechanical start: spinning the shaft manually is impossible due to the high pressure in the system and the tightness of the housing.
The third way is to rewind the stator. This is the only real way to “create” a starting winding if the old one burns out. The technician removes the burnt wires and winds new ones, observing the number of turns and the laying pattern. This is a complex process that requires special equipment and skills, but it returns the engine to factory specifications.
⚠️ Attention: Wiring diagrams found on the Internet often do not take into account the starting currents of refrigeration compressors, which are 5-7 times higher than the nominal ones.
Risks and consequences of working on one winding
Operating a refrigerator Bosch or Liebherr with a faulty or excluded starting winding carries serious risks. The first thing that suffers is thermal protection. The starting relay and thermal relay are designed for short-term operation of the starting winding. If you try to start the motor without it, the current in the working winding will remain high constantly, which will lead to the protection tripping or its burnout.
The second critical factor is oil. In the compressor, oil is sprayed onto the rubbing parts due to the operation of the engine. If the rotor hums but does not rotate or rotates at low speed, lubricant is not reaching the bearings and piston group. This causes dry friction, metal scuffing and (ultimately) piston wedging.
In addition, the vibration that occurs when trying to start without a phase shift destroys the soldering of the tubes. Copper condenser and evaporator tubes may burst, causing refrigerant leakage. Restoring the system after this will require evacuation, refilling with freon and replacing the filter-drier.
☑️ Diagnosis of winding faults
Comparison of characteristics: normal mode and emergency start
For clarity, let's look at how the engine operating parameters change when trying to bypass the standard circuit. The table shows comparative data for a typical 1/5 hp compressor.
| Parameter | Normal mode (2 windings) | Start attempt (1 winding) | Consequences |
|---|---|---|---|
| Starting current | Short burst | Continuous high current | Wiring burnout |
| Torque | Sufficient for compression | Absent or small | Piston wedge |
| Stator temperature | Operating (up to 80°C) | Critical (>150°C) | Insulation destruction |
| Bearing life | Normal | Sharply reduced | Noise and vibration |
As can be seen from the table, the economic effect of trying to save During winding repairs, it is completely absent. You risk getting a completely inoperable unit that will have to be thrown away. Even if the engine can be spun externally, it will not be able to create the pressure necessary to circulate freon in the system.
Why does the starting winding burn out?
The starting winding is made of a thinner wire and has greater resistance. It is designed for short-term operation (1-3 seconds). If the starting relay sticks and does not open the circuit, the winding burns out first.
Diagnostics and identification of winding faults
Before drawing conclusions about a burnt out winding, it is necessary to carry out proper diagnostics. Often the problem lies not in the motor itself, but in the start relay or capacitor. To check you will need a multimeter. First, unplug the refrigerator and remove the casing from the compressor.
Remove the starting and protective relay. Check the winding contacts. Typically, a compressor has three terminals: common, starting and working. It is necessary to ring pairs of contacts. The resistance between general and working should be minimal, between general and starting - slightly higher, and between working and starting - total.
- 📉 Open circuit: if the multimeter shows infinity, the winding is burned out or the wire inside is broken.
- 🔥 Short circuit: if the resistance is close to zero, an interturn has occurred short circuit.
- 🛡️ Breakdown to the housing: if there is resistance between the leads and the copper tube, the motor is faulty and dangerous.
If the diagnostics showed that the starting winding is really broken, there are few options. Rewinding at home is almost impossible due to the difficulty of accessing the stator and the need for special impregnation with varnish under vacuum. The only sure way is to replace the motor-compressor with one of similar power and cooling capacity.
Practical recommendations for restoration
If you are faced with a situation where the refrigerator hums but does not start, and diagnostics have confirmed a problem with the windings, do not try to use “traditional methods” of starting. This may cause a fire. The best solution would be to call a technician or replace the compressor yourself if you have the skills to solder copper pipes and work with a vacuum pump.
When choosing a new compressor, pay attention not only to the power, but also to the type of refrigerant (R134a, R600a) and the type of oil (mineral, synthetic). Incorrect selection of oil can lead to the formation of plugs in the capillary tube and system failure.
It is also important to check the condition of the capacitor (if it is in the circuit) and the starting relay. Often, replacing these cheap parts brings the refrigerator back to life without having to get into the engine hardware. Modern relays can be solid-state; they are more reliable than mechanical ones, but are sensitive to voltage surges.
⚠️ Attention: Technical characteristics of compressors and oil requirements may vary depending on the model. Always check the manufacturer's technical documentation before replacing components.
Frequently asked questions (FAQ)
Is it possible to start a refrigerator if it is burned out? starting winding using a powerful capacitor?
Theoretically, connecting a capacitor can create a phase shift, but choosing a capacitance for a powerful compressor is very difficult. In addition, constant operation through a capacitor is not provided for by the design, which will lead to overheating and eventual combustion of the engine. This is a temporary and risky solution.
Why does the compressor hum but does not start?
This is a classic sign of a faulty starting system. Either the starting winding has burned out, or the starting relay is stuck, or the capacitor has failed. Also, the cause may be a wedge of the piston group due to lack of oil or mechanical damage.
Is it worth rewinding the refrigerator compressor yourself?
No, this is not advisable. Rewinding requires removing the stator, removing the old winding (which is difficult without damaging the plates), winding a new wire according to special tables, laying it, impregnating it with varnish and drying. The cost of work and the risk of error exceed the cost of a new compressor.
How to determine which winding has burned out?
You need to test the windings with a multimeter. The starting winding usually has a higher resistance than the working winding. If on one of the pairs of contacts the resistance is infinite (open) or close to zero (short circuit), then this winding is faulty. Most often, it is the starter that suffers because of the thin wire.