Analysis of common failure causes of hermetic refrigeration compressors

Analysis of common failure causes of hermetic refrigeration compressors 1. How to identify the 3 terminals on the casing of a hermetic compressor?

The resistance between running terminal (R), starting terminal (S), common terminal (C), RS is greater than the resistance between SC and RC. The resistance between RS is equal to the resistance between SC and the resistance between RC.

The above rules can be used to distinguish. It should be noted that the resistance value of the terminal temperature rise tester of the three-phase compressor is equal.

2. How to judge the compressor motor winding short circuit?

Use a multimeter to select the resistance gear, and after zero adjustment, measure the resistance value of the compressor motor winding C-R or C-S. If the measured winding resistance value is less than the normal value, it can be judged that the winding is short-circuited.

Three-phase compressor:

◆ The resistance value measured 2 times is infinite, indicating that one set of windings is open;

◆ All three tests are infinite, indicating that at least two sets of windings are open;

◆ The resistance value measured in 2 of the 3 measurements is significantly lower than the other measurement, indicating that there is a short circuit.

3. How to judge that the compressor motor hits the shell and passes the ground?

Use the resistance file of the multimeter. Then put one pen tightly against the common point, and another test pen tighten the compressor process tube to expose the metal part, or take off a small piece of paint on the shell plate for measurement. If the resistance value is very small, it can be judged that the winding or internal wiring touches the shell through the ground.

4. How to judge that the compressor motor winding is open?

Adjust the multimeter to the resistance range, connect the test leads to the terminals of any two windings, and measure the resistance value. If the winding value is infinite, that is, there is no conduction between the terminals of the two windings, it can be judged that the winding is open. 5. What to check if the compressor does not start?

◆ Check whether the compressor is overloaded, the pressure switch, and the overcurrent protector are tripped or damaged.

◆ Check the room temperature sensor and tube temperature sensor for open circuit or poor contact, or short circuit.

◆ Check whether the relay is closed, the compressor is open or short-circuited, and the compressor capacitor is broken.

6. What are the reasons for the compressor to be overheated and stop soon after starting?

◆ The refrigerant is insufficient or excessive, the capillary assembly is blocked, and the inside of the four-way valve is leaking.

◆ The compressor itself malfunctions, such as short circuit, open circuit, contact with the shell and ground.

◆ If the high pressure pressure is too high, the pressure relay will act.

◆ The condenser is poorly ventilated or the air flow is short-circuited, or the system is mixed with non-condensable liquid gas.

◆ The ambient temperature of the outdoor unit is too high.

◆ Compressor jammed cylinder or hung shaft.

7. The performance of low compressor efficiency

Generally, the discharge pressure drops, the suction pressure rises, and the temperature of the compressor cylinder head and suction and discharge chambers is too high.

8. Judgment of the compressor's inability to work

First test whether the suction port is inhaled, and then test whether the exhaust port is exhausted, and block the exhaust port with your hand. If you feel that the pressure is not very large, or even there is no exhaust, it can be considered that the compressor has lost its working ability.

9. Why is the compressor motor too current?

There is a short circuit between the compressor turns, but the fuse is not blown. The "secondary friction" of the compressor destroys the smoothness of the friction surface, causing the compressor's power and current to increase, but it has not reached the level of "holding shaft" or "cylinder jamming", preventing the compressor from rotating.

Use a multimeter to check the insulation resistance of the compressor to the ground. Normally, it should be above 2MΩ. If it becomes smaller or close to zero, it indicates a short circuit. If the insulation resistance to ground is normal, check the resistance value of the starting and running windings. [This article is from the public number of Refrigeration Encyclopedia] If there is a short circuit between turns, the operating current increases.

10. What are the reasons for the difficulty in starting the three-phase compressor motor?

◆ The power supply voltage is too low and the compressor motor winding is short-circuited.

11. How to troubleshoot the problems that the speed of the three-phase compressor motor slows down, the fuse of one phase is blown, and the current of one phase increases during operation?

◆ It is often caused by the fact that the windings of the compressor motor are connected to the ground. After removing the ground wire, use a test pencil to test whether the case is live. If the casing is live, rewind the compressor motor winding or replace the compressor.

12. How to eliminate the "whooping" sound from the three-phase compressor motor during operation?

◆ The three-phase compressor motor emits "wheezing" during operation, which is caused by the serious imbalance of the three phases. One phase of the power supply is missing, and the three phases can be restored.

13. How to exclude the reverse rotation of the three-phase compressor motor?

◆ It is caused by wrong wiring, just change two wires of the three-phase arbitrarily.

14. Compressor replacement sequence and points of attention

◆ R22 is a non-flammable gas, but if it comes into direct contact with a high-temperature flame, it will produce toxic gas. Therefore, before welding, release the refrigerant in the refrigeration system.

◆ R32 is a flammable and explosive refrigerant. Our Refrigeration Encyclopedia has repeatedly emphasized the characteristics of this refrigerant. Any R32 refrigeration equipment involved in the maintenance of the refrigeration system requires replacement of parts, it must be vacuumed before operation! Be careful not to introduce fire sources!

◆ R410A is low-toxic, non-flammable and non-explosive. To replace the compressor, you must use the R410A compressor, and definitely not install the R22 compressor. When replacing the valve, there is a special mark on the valve body of R410A

15. What are the types of compressor overload protectors for air conditioners?

◆ External overload protector; embedded overload protector.

16. What are the protections of compressors?

◆ Overload protector: Mainly used for overcurrent and overheat protection of compressor motor.

◆ Internal protector: It mainly protects the compressor motor from overcurrent.

◆ Thermal relay: Mainly used for line overcurrent protection of three-phase compressor motors.

◆ Reverse phase preventer: Mainly used for three-phase rotary compressors to prevent the compressor from reversing the direction of rotation or lacking phase energy.

17. What are the common reasons for overload protectors?

◆ The power supply voltage is too low and the symmetry of the three-phase voltage is poor.

◆ The compressor motor runs at low speed for extended time.

◆ The compressor motor runs at low voltage for a long time with load.

◆ The cooling medium passage of the compressor motor is blocked.

◆ The operating environment temperature is too high.

18. What is the hydraulic shock of the compressor?

◆ The refrigerant does not completely evaporate in the evaporator, causing the refrigerant to be sucked back by the compressor in wet vapor or liquid form, causing liquid shock to the compressor.

◆ The hydraulic shock will cause damage to the valve disc, valve plate, and piston. In severe cases, the connecting rod may be deformed and even the compressor may be damaged.