Why does the refrigeration compressor produce overheat protection What matters should be paid attention to in the use of overload protector

Why does the refrigeration compressor produce overheat protection What matters should be paid attention to in the use of overload protector

1. Why does the compressor produce overheat protection?

The working principle and classification of the overload protector. The overload protector of the compressor for air conditioning generally adopts a snap-type bimetallic protector, which consists of a heating wire, a bimetallic sheet and two static contacts, which are connected in series in the compressor circuit. .

When the current in the circuit is too large, the heating wire will heat up and bake the dish-shaped bimetallic plate. When the bimetallic plate heats up, it will arch in the opposite direction, causing the contact to be disconnected; when the compressor housing or motor temperature is too high When the working current is normal, the heating wire generates little heat.

　　 The bimetallic strip will also deform and bend upwards, break away from the two static contacts, and cut off the circuit. This kind of protector can reset automatically, and has the double protection function of over current and over temperature rise.

Second, the working principle and classification of overload protectors

　　1. The working principle of overload protector

　　A. Refrigeration compressor overload protectors used in general refrigeration systems are all snap-type bimetallic protectors.

　　B. This kind of protector is mainly a complete circuit composed of a heating wire, a 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 baked 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. More convenient is that this protection can be automatically reset, so it is very convenient during use.

　　 2. Classification of overload protectors

　　 Under normal circumstances, overload protectors are classified according to different installation methods, and are mainly divided into external and built-in overload protectors:

　　A. Introduction to external overload protector

　　The external overload protector is generally installed on the sealed terminal of the refrigeration compressor shell, and must 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, there is a process from the heat of the shell to the perception of the overload protector, so 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: the lashing type and the plug-in type: the lashing type overload protector, as the name suggests, is tied to the motor coil to directly induce the temperature change of the coil. The advantage is that the response is very sensitive and accurate;

　　Plug-in overload protector means that the protector is installed directly on 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 type 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 type of protector is useless.

　　 So overall: the external overload protector is not as sensitive, accurate, and reliable as the built-in type in terms of use effect, but its cost is relatively much lower, so it also has 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 overload protector is several times higher than that of the external type. Therefore, friends can make corresponding choices according to their own conditions and requirements.

　　 Three, the matters needing attention during the use of the overload protector

a. Depending on the configuration of the refrigeration compressor overload protector, the protection effect of the refrigeration compressor is completely different. Overall, the sensitivity and accuracy of the built-in overload protector are much higher than those of the external overload protector. Therefore, it has a much greater protective effect on the refrigeration compressor;

　　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 generally needs to add special protection for the lack of refrigerant;

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

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