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Application of Frequency Converter in Refrigerator

In contemporary society, with the development of the refrigeration industry, the application of refrigeration has become increasingly widespread, and has now penetrated into all fields of people's life, production, and scientific research activities, and has played a huge role in improving the quality of human life. From daily clothing, food, housing and transportation, to cutting-edge science and technology, refrigeration is inseparable.


Introduction of screw refrigeration compressor:

The screw refrigeration compressor refers to a refrigeration compressor that uses one or two rotors (screw) with a spiral groove to rotate in the cylinder to compress the gas.

The energy regulation methods of screw refrigeration compressors mainly include suction throttling regulation, turn-stop regulation, frequency conversion regulation, slide valve regulation, plunger valve regulation, etc. At present, the commonly used energy adjustment method is slide valve adjustment. This adjustment method is to install a regulating slide valve on the body of the screw compressor to become a part of the compressor body. It is through the movement of the slide valve that the inter-tooth primitive volume of the compressor's female and male rotors is still connected to the suction hole through the return hole of the slide valve within a period of time before the contact line of the tooth surface moves from the suction end to the discharge end. The ports are connected, and part of the gas is returned to the suction port, that is, the effective working length of the rotor is changed to achieve the purpose of energy regulation. The adjustment range is generally stepless adjustment within 10% to 100%. During the adjustment process, the power and the gas transmission volume are almost in direct proportion to the load operation when the gas transmission volume is above 50%, but below 50%, the performance coefficient will decrease correspondingly, which appears to be less economical. The motor power of screw refrigeration compressors is generally above 100kw. Since the motor speed does not change, the power consumption is relatively large during the adjustment of the slide valve, so there is a serious "big horse-drawn cart" phenomenon in the cold storage.


Frequency conversion regulation of screw refrigeration compressor:


Freezers are used for freezing and refrigerating food. Therefore, in the food industry, the use of refrigerators is very common. With the development of frequency conversion technology, frequency converters are also being used more and more in the control of refrigerators.


1. The purpose of using the inverter


Inverter control (variable compressor capacity control) is used for the compressor in the refrigerator, so that the refrigerator can always operate with high efficiency close to the design conditions in response to changes in the refrigeration load. The main advantages of inverter-controlled refrigerators are as follows:


1) Energy saving: Change the compressor speed according to the change of cooling load, so that it always runs at the optimum point. Thereby reducing the required power.


2) Constant temperature: continuous capacity control can make the temperature of refrigerated products change little. In addition, even if the cooling load is temporarily increased, the temperature change of the refrigerated product can be reduced by means of acceleration.


3) Improvement of refrigeration capacity: The capacity of the compressor directly connected to the airtight motor in the 50Hz region is only 80% of that in the 60Hz region, while the inverter control can, regardless of the power frequency, always maintain a certain capacity.


4) Soft start: The start-up time of the inverter can be customized according to the site conditions, which can reduce the large current impact of the power frequency start on the power grid and prolong the service life of the mechanical parts.


2. Frequency conversion control of refrigeration compressors


Taking a single unit as an example, the description is as follows: According to the requirements of the on-site process, the inverter should realize external control, should have two sets of industrial frequency conversion starting systems, frequency conversion fault alarm function, and external ammeter to monitor the motor current (or input current), etc.