Wedging of the refrigerator compressor: what diodes are needed

The situation when the refrigerator stops cooling, and the motor hums for several seconds and stops, is familiar to many owners of household appliances. Most often, this indicates that the piston group is stuck at a dead center, and the engine does not have enough starting force to take off. Masters call this condition a “wedge,” and it is to eliminate it that the method of applying increased voltage or a direct current pulse is often used.

The question of what is needed for wedging arises among those who are trying to revive the unit on their own, using time-tested but dangerous methods. The essence of the method is to include a powerful semiconductor element in the circuit of windings, which passes only one half-wave of an alternating current sinusoid. This creates a pulsating current that can stir up a jammed shaft. what diodes necessary for wedging, occurs among those who try to revive the unit on their own, using time-tested but dangerous methods. The essence of the method is to include a powerful semiconductor element in the circuit of windings, which passes only one half-wave of an alternating current sinusoid. This creates a pulsating current that can loosen a jammed shaft.

However, before looking for components, you need to understand that wedging is a last resort. The success of the operation depends not so much on the brand of the diode, but on the condition of the compressor itself and the cause of the jam. If a mechanical scuff has formed inside the mechanism or the winding has burned out, no diodes will help, but will only finally finish off the unit.

The principle of operation of the current wedging method

A standard asynchronous refrigerator motor is started by a starting winding and a starting relay. When the rotor is stuck, the standard magnetic field is not enough to overcome the frictional force. The wedging method is based on short-term supply to the starting winding of a current several times higher than the rated current, or changing its shape.

The use of a diode allows you to pass only a positive (or negative) half-wave voltage of 220 volts through the winding. As a result, the effective voltage decreases, but the nature of the current changes. The motor begins to vibrate at twice the mains frequency, and if the jamming is not strong, the shaft breaks away. It is important to notethat this process is accompanied by sudden heating of the windings.

There is a misconception that the diode increases the voltage. In fact, it changes the shape of the signal. For wedging, a circuit is often used where a diode is connected in series with the starting winding for a short time. This creates a powerful burst of torque.

Be aware of the risks. The supply of direct or pulsating current to a winding designed for alternating current causes its intense heating. The exposure time should not exceed a few seconds, otherwise the insulation of the wires will melt and the compressor will have to be thrown away.

⚠️ Attention: The diode wedging method is a barbaric repair method. It does not guarantee a result and often leads to a complete interturn short circuit. Use it only if replacing the compressor is not economically feasible or is impossible right now.

Which diodes are suitable for compressor wedging

The choice of semiconductor element is critical for the safety of the technician and the safety of the equipment. Conventional low-power diodes, such as the popular ones, will burn out instantly the first time they are turned on, since they are not designed for high motor starting currents. This task requires powerful rectifier diodes. 1N4007, will burn out instantly the first time they are turned on, since they are not designed for high motor starting currents. This task requires powerful rectifier diodes.

Diodes of the D242, D243, D245, D246 or D247series are considered the optimal choice. These Soviet-made components are specially designed to operate in circuits with currents of up to 10 amperes or more. They have a massive metal body that serves as a radiator for heat removal, although with a short-term pulse this is not as critical as with constant operation.

You can also use imported analogues, for example, series diodes 10A10 or any others with markings indicating a forward current (If) of at least 10 Amperes and a reverse voltage (Vrrm) of at least 400-600 Volts. The reverse voltage parameter is extremely important, since at the moment of a circuit break, voltage surges can occur that break through weak elements.

Below is a table of the main characteristics of suitable diodes, which you should focus on when searching for components:

At When assembling the circuit, make sure that the diode contacts are securely fastened. The use of “crocodiles” or hanging twists is unacceptable due to the risk of sparking and heating of the joints. The diode must be connected to the break in the wire going to the starting winding.

Connection diagrams and sequence of actions

To implement the wedging method, it is necessary to assemble a simple circuit. You will need the diode itself, two wires with clamps, a button (preferably without locking, for example, from a doorbell) and access to the compressor contacts. The standard circuit involves connecting a diode in series with the starting winding.

First you need to remove the starting relay from the compressor. The contact group usually has three terminals: common (C), starting (S) and working (R). We need to apply voltage to the trigger pin through a diode. At this moment, it is better to power the working winding directly or through a standard relay so that the engine tries to operate in normal mode while the starting winding receives an impulse.

The process is as follows way: you apply power to the working winding, the compressor hums. At this moment, you briefly (for 1-2 seconds) close the starting winding circuit through the diode. If the shaft is alive, you will hear a characteristic click or the hum will change tone, and the motor will start.

There is a more aggressive method when the starting winding is “ringed” with a diode without applying voltage to the working winding. This creates a vibration that sometimes breaks the wedge. However, this method is less predictable. The main rule is not to keep the circuit closed for more than 3-5 seconds.

⚠️ Attention: All manipulations are carried out under a voltage of 220 Volts. The risk of electric shock is extremely high. Do not touch exposed wires and metal parts of the compressor while powering up.

Safety precautions and necessary precautions

Working with high voltage and faulty equipment requires maximum concentration. A refrigerator compressor is not just a motor, it is a vessel under refrigerant pressure. Careless handling can lead not only to electric shock, but also to a fire or explosion.

Before starting work, be sure to unplug the refrigerator and let it cool down, if it was working before. Check the integrity of the insulation on the wires you plan to use. Any microcrack in the insulation at a voltage of 220V can be fatal.

Use tools with insulated handles. The diode can become very hot during operation, so do not hold it with your fingers during the experiment. It is better to fix it on a dielectric substrate or use clamps.

Ensure good ventilation in the room. If the compressor does burn out, there may be a smell of burnt insulation and oil. It is also worth considering that if wedging is unsuccessful, the valve group may be damaged, and the compressor will stop pumping freon, even if it starts.

Why may the method not work?

If the compressor is jammed due to lack of oil or mechanical destruction of the piston group (scuffing, broken connecting rod), electrical wedging no use. The shaft physically cannot turn. In such cases, only replacing the unit helps.

Alternative ways to start a jammed motor

If you don’t want to tinker with diodes or they don’t help, there are other methods that are sometimes more effective. One of them is the “swing” method. The idea is to briefly apply voltage first to the working winding, then to the starting winding in different sequences in order to loosen the shaft.

Another method is to use a special device called a “Start-up” or a universal starting relay with a forced start button. Such devices often have built-in protection and dose the pulse more competently than a homemade circuit with a diode.

The mechanical method involves tapping the compressor body with a wooden or rubber mallet when trying to start. Vibration helps dislodge jammed parts. However, hitting the compressor with metal objects is strictly prohibited - you can puncture the housing or damage the tubes.

Sometimes heating the compressor housing helps. If you let the motor run (or simply heat it with a hairdryer) for 15-20 minutes, the metal will expand and the gap between the rubbing parts may increase, which will allow the shaft to break off. But this method is risky for the windings.

Diagnostics of results and further actions

After successfully starting the compressor, you cannot immediately close the casing and consider the job done. A thorough diagnosis is necessary. First of all, check the current consumption using a current clamp. If the current significantly exceeds the nominal value (indicated on the nameplate, usually 0.5-1.0 A for household refrigerators), then there is an interturn short circuit in the windings.

Listen to the sound of the running motor. Metallic knocking, clanging or excessive vibration indicate that mechanical damage has not gone away. Such a compressor will not last long and may stop again at any moment.

Check the outlet pressure. To do this, you need to carefully cut the filling tube (after bleeding off the freon, if there is any left, or connecting a pressure gauge station). If the compressor does not produce the required pressure, its performance has dropped and it will not cool normally.

If after wedging, the compressor works, but the housing heats up to temperatures above 80-90 degrees, its service life is calculated in days or weeks. In this case, it is better to immediately plan the purchase of a new unit so as not to lose food.

Frequently asked questions (FAQ)

Is it possible to wedge a compressor without a diode by simply supplying 220V directly?

Supplying 220V directly to the starting unit winding without a diode is possible, but less effective for breaking the wedge, since it does not create the necessary ripple. However, this creates a huge risk of burning out the starting winding in a split second. The diode in this circuit plays the role of a limiter and pulse shaper.

Which diode definitely cannot be used for wedging?

It is strictly forbidden to use diodes from electronics power supplies (small black cylinders), Schottky diodes with low reverse voltage and any elements rated for a current of less than 5 Amperes. They will instantly explode or burn.

How long can you keep the diode in the circuit when wedging?

The switching time should not exceed 2-3 seconds. After each attempt, allow the compressor to cool for at least 10-15 minutes. Long-term exposure will lead to thermal breakdown of the winding insulation.

Will wedging help if the compressor burns out?

No. If the windings are already broken or there is a short circuit (interturn) on the housing, wedging will not help. At best, you will not get results, at worst, you will finish off the remaining parts of the engine. First, ring the windings with a tester.

Is it necessary to change the oil after wedging?

The wedging method does not involve opening the system, so the oil does not change. However, if there were combustion products or metal shavings from scuffing inside, they will remain in the system. This is one of the reasons why such compressors are considered “disposable” after resuscitation.