Why does the compressor produce overheating protection?
a. The refrigeration compressor overload protectors used in general refrigeration systems are all sudden-jump bimetal overload protectors.

b. This kind of protector is mainly a complete circuit composed of heating wire, bimetal and two static contacts, and then connected in series to the circuit where the refrigeration compressor is located.

c. Its working principle is that when the current in the system circuit increases for no reason, the heating wire will generate a lot of heat. When the bimetallic sheet is heated by the heat of the heating wire, it will become reverse arched, thereby achieving the purpose of disconnecting from the electric shock and cutting off the entire circuit.

d. Even if the current in the circuit is very small, but the temperature of the refrigeration compressor housing or motor is too high, the same phenomenon will occur. So as to effectively protect the safe operation of the refrigeration compressor. The more convenient thing is that this kind of protection can be reset automatically, so it is very convenient during use.

2. Classification of compressor overload protector
Under normal circumstances, compressor overload protectors are classified according to different installation methods, and are mainly divided into external and built-in overload protectors:

a. Introduction of external overload protector
The external overload protector is generally installed on the sealed terminal of the refrigeration compressor shell and should be kept close to the upper cover. So as to ensure that the temperature abnormality on the refrigeration compressor shell is sensitively sensed;

Because there is a process of conduction and convection from the heat of the motor to the shell of the refrigeration compressor, the accuracy and reliability of this method are not particularly good. Therefore, the reason why the external overload protector is widely used is more because its manufacture is relatively simple and the cost is relatively low.


At the same time, the external overload protector has obvious advantages such as convenient installation and maintenance, so it is used more in some low-power electrical aspects;

b. Introduction of built-in overload protector
The built-in overload protector is subdivided into two types: lashing type and plug-in type:
The lashing type overload protector, as the name implies, is tied to the motor coil, so as to directly induce the temperature change of the coil. The advantage of this kind of protector is that the response is very sensitive and accurate;

The plug-in overload protector is the installation method of the protector is directly plugged into the sealed terminal. The main principle is to sense whether the temperature of the motor is normal through the heat conduction of the refrigerant. This kind of protector has certain limitations, that is, it is very sensitive when the refrigerant does not leak, but if there is a refrigerant leak, this kind of protector will be useless.

Relatively speaking:
The external compressor overload protector is not as sensitive, accurate, and reliable as the built-in compressor. But its cost is relatively much lower, so there is a certain market space. But compared to the built-in type, the scope of adaptation is still much smaller. However, the cost of the built-in compressor overload protector is several times higher than that of the external compressor. Therefore, customers can make corresponding choices according to their own conditions and requirements.

3. Matters needing attention during the use of the overload protector
A. The overload protector of the refrigeration compressor has a completely different protective effect on the refrigeration compressor according to its configuration. Overall, the sensitivity and accuracy of the built-in overload protector are much higher than those of the external overload protector. Therefore, its protective effect on the refrigeration compressor is also much greater;

B. In the case of insufficient refrigerant or leakage, the protective effects of the two overload protectors are very limited. Therefore, in order to prevent inadequate protection, a complete refrigeration system must generally be equipped with special protection for insufficient refrigerant;

C. In the case of too much refrigerant, the protective effect of the two overload protectors is also limited. Therefore, there must be corresponding supplementary measures to ensure that the refrigeration compressor is not harmed;

D. In the case of high compression ratio, the protective effect of the overload protector is also very weak. Therefore, a separate low-pressure protection measure is also needed to protect the refrigeration compressor.