The core problem of compressor oper
Precautions for the use of refrigeration compressor overload protector
Overload protectors for compressors used in air conditioners generally use snap-on bimetallic protectors, consisting 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, which will disconnect the contacts; when the compressor housing or motor temperature is too high When the working current is normal and the heating wire generates little heat, the bimetal will 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.
According to the different installation methods, it can be divided into external type and built-in type.
1, external protector
is installed on the sealed terminal of the compressor shell, close to the upper cover to sense the temperature of the compressor shell. Since there is a process of conduction and convection from the heating of the motor to the heating of the shell, and another process from the heating of the shell to the action of the protector, the accuracy and reliability of this protection method are relatively poor, but due to its simple manufacturing , The same bimetallic sheet, by adjusting the height of the screw, can produce different protectors, and the installation and maintenance are convenient, and the cost is low, so it is generally used in low-power household air-conditioning compressors.
2, built-in protector
It is divided into lashing type and plug-in type. The lashing type is to tie the protector and the motor coil together to directly sense the temperature change of the coil, and the response is quick and accurate; the plug-in type is to plug the protector into the sealed terminal The abnormal temperature of the motor is induced by the heat conduction of the refrigerant, and the protection is more accurate when the refrigerant does not leak, but once the refrigerant leaks, the protection performance is poor.
In short, the built-in protector is more sensitive and accurate to the temperature of the motor than the external type, has higher reliability, and has a wider range of applications (general air conditioner compressors can be applied). However, because it is installed inside the compressor, it requires a small size and can adapt to the harsh environment such as high temperature and high pressure changes inside the compressor. High requirements are placed on its design and manufacturing, and the cost is several times more expensive than the external type.
Precautions:
1. Different compressor overload protectors have different protective effects on the compressor. The built-in protector has higher sensitivity than the external protector and has a greater protective effect on the compressor.
2. When the refrigerant is insufficient, the protective effect of the built-in protector or the external protector on the compressor is very limited, so the air conditioning system needs to increase the protection against the refrigerant shortage.
3. When the refrigerant is too much, the overload protector cannot play a protective role. The system needs to use high-voltage protection measures such as high-voltage switches to avoid damage to the compressor caused by too much refrigerant.
4. In the case of high compression ratio, the overload protector cannot play a protective role, and another low-pressure protection measure must be provided to protect the compressor.
