The compressor is regarded as the heart of the refrigeration system, and the term that best expresses the characteristics of the compressor is called "vapor pump". The actual responsibility of the compressor is to raise the pressure, from the suction pressure state to the discharge pressure state.

Compression ratio is a technical expression of pressure difference, which means the absolute pressure on the high pressure side divided by the absolute pressure on the low pressure side. Compression ratio calculations must use absolute pressure values. To avoid negative compression ratio calculations, absolute pressures, not gauge pressures, must be used when calculating pressure ratios. The absolute pressure value is used to make the calculated value of the compression ratio a positive value, which is meaningful.

There are five types of compressors used in the refrigeration and air conditioning industry: reciprocating, screw, rotary, scroll and centrifugal, of which reciprocating is the most widely used compressor in small and medium commercial refrigeration systems. Screw compressors are mainly used in large commercial and industrial systems. Rotary compressors and scroll compressors are mainly used in household and small-capacity commercial air-conditioning units, while centrifugal compressors are widely used in air-conditioning systems in large buildings.

Various reciprocating compressors are generally classified according to the form of the compressor housing and the setting of the drive mechanism. According to the shell form, there are open type and closed semi-hermetic compressors. The closed type means that the entire compressor is arranged in a casing.

Compressor main performance Compressor input, output power, coefficient of performance, cooling capacity, starting current, running current, rated voltage, frequency, cylinder volume, noise, etc. To measure the performance of a compressor, mainly from the comparison of weight, efficiency and noise.

According to Chinese standards, its safety performance inspection is carried out according to the items specified in GB4706.17-2004. The main items are electric strength, leakage current, locked rotor, and overload operation test.

The performance inspection of the air conditioner compressor shall be carried out in accordance with the provisions in GB5773-2004.