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1. Why does compression create overheating protection?
Overload protector of the working principle and classification of air conditioner compressor overload protector relay, are generally adopts double metal protector, the heating wire, bimetallic strip and of two static contact circuit, in series in the compressor circuit.
When the current in the circuit is too large, heat the wire and bake the saucer bimetal sheet. When the bimetal sheet is hot, it will arch in the opposite direction and break the contact. When the compressor housing or motor temperature is too high, even if the working current is normal, the heating wire generates little heat.
The bimetal sheet also deforms and bends upward, disengaging from two static contacts and cutting off the circuit. This kind of protective device can be reset automatically and has the dual protection function of over current and over temperature rise.
Working principle and classification of overload protector
1. Working principle of overload protector
A. The overload protector of refrigerating compressor used in general refrigeration system is a jump type bimetal protector.
B. this protector is mainly a complete circuit composed of heating wire, bimetallic sheet and two static contacts, and then connected to the circuit where the refrigeration compressor is located.
C. the working principle is that when the current in the system circuit increases without 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 inverted arch, so as to disconnect from the electric shock, cutting off the whole circuit.
D. even if the current in the circuit is small, the same phenomenon will occur when the housing or motor temperature of the refrigeration compressor is too high. So as to effectively protect the safe operation of the refrigeration compressor. More convenient is that the protection can be reset automatically, so it is very convenient to use.
2. Overload protector classification
In general, overload protectors are classified according to different installation methods, which are mainly divided into external and internal overload protectors:
A. Introduction to the external overload protector
External type overload protector are generally installed on the compressor shell seal terminal post, keep close to the cover, so as to ensure sensitive perception to the refrigeration compressor shell temperature anomaly;
Because of heat transfer from the motor to the compressor shell has a process of conduction and convection, heat from housing to be overload protector to perceive there is a process, therefore the veracity and reliability of this approach is not particularly good. Therefore, the reason why the external overload protector is widely used is more because of its simple manufacture and low cost.
At the same time, the external overload protector has obvious advantages such as convenient installation and maintenance, so it is used more in some small power electrical aspects.
B. Introduction of built-in overload protector
Built-in overload protector and colligation and splice is subdivided into two kinds: strap-on overload protector just as its name implies is with the motor coil binding, thereby the purpose of the induction coil temperature changes directly, the protector has the advantage of reaction is very sensitive and accurate;
The plug-in overload protector is the installation method of the protector, which is directly connected to the sealing terminal post. The main principle is to perceive whether the temperature of the motor is normal through the heat conduction of the cold medium. The protector has certain limitation, that is, under the condition of the refrigerant no leakage is very sensitive, but if there is leakage of refrigerant, the protector is useless.
So in general: external type overload protector on the use effect of relatively less sensitive, accurate and reliability of the built-in also want far worse, but its cost is relatively lower, therefore also has the certain market space. But the range of adaptation is much smaller than the built-in one. But the cost of an internal overload protector is several times higher than that of an external one. Therefore, friends can make corresponding choices according to their own conditions and requirements.
Iii. Matters needing attention during the use of overload protector
A, compressor overload protector according to the different way of its configuration, for the protective effects of refrigeration compressor are completely different, sensitivity and accuracy of the overall built-in overload protector is much higher than the outer type overload protector, so it for refrigeration compressor protection is much larger;
B, under the condition of the refrigerant are insufficient or leaking, two kinds of overload protector protective effect is very limited, so in order to prevent the lack of protection, a complete refrigeration system is typically add specialized protection against the cold media;
C. In the case of too many refrigerants, the protective effect of the two overload protectors is also limited, so corresponding supplementary measures should be taken to ensure that the refrigeration compressor is not damaged;
D. In the case of high compression ratio, the protective effect of overload protector is very weak. Therefore, it is necessary to separately set low-pressure protective measures to protect the refrigeration compressor.