Control system of variable-frequency refrigerated dryer

Abstract

The invention relates to the technical field of dryers, in particular to a control system of a variable-frequency refrigerated dryer, which is composed of the following three controls: superheat degree adjustment, dew point temperature adjustment and protection mechanism through an electronic expansion valve, low-frequency pre-operation of the dryer after the dryer is started, and operation of a compressor according to a set lower limit frequency. The electronic expansion valve adjusts the degree of superheat, specifically, when the degree of superheat is higher than a target value after pre-operation, the opening degree of the electronic expansion valve is increased, and when the degree of superheat is lower than the target value, the opening degree of the electronic expansion valve is reduced, and the degree of superheat reaches a constant range, the electronic expansion valve stops adjusting at the moment. The variable-frequency refrigeration dryer can dynamically balance the high pressure and the low pressure of a refrigerant system, enables the frequency and the dew point of compressed air to be stable, ensures that equipment is kept in a safe working range under various operation conditions, and not only improves the reliability of the system, but also prolongs the service life of the equipment through the protection mechanism.

Description

Technical Field

[0001] The invention relates to the technical field of dryers, and in particular to a control system of a variable frequency refrigeration dryer. Background Art

[0002] The variable frequency cold dryer is an advanced air drying equipment that adjusts the dew point temperature during the drying process by precisely controlling the operating frequency of the compressor. The core of this equipment lies in its variable frequency drive technology, which can dynamically adjust the working state of the compressor according to actual needs to ensure that the dew point temperature is stable within the preset ideal range. When working, the variable frequency cold dryer will continuously monitor the temperature changes in the drying chamber and intelligently adjust the operating speed of the compressor accordingly. This sophisticated control method enables the equipment to achieve highly accurate temperature management while maintaining high efficiency, thereby ensuring the consistency and reliability of the air drying effect. The variable frequency cold dryer controls the opening of the thermal expansion valve by detecting the evaporation temperature.

[0003] For the above technical conditions, the control of the opening of the thermal expansion valve and the frequency of the compressor by the evaporation temperature alone is unstable. At the same time, the adjustment rate is too fast, resulting in an unstable dew point of the compressed air.

[0004] Based on this, the present invention designs a control system of a variable frequency refrigerated dryer to solve the above problems. Summary of the invention

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a control system for a variable frequency refrigerated dryer, which is composed of the following three controls, namely, superheat regulation, dew point temperature regulation, and protection mechanism through an electronic expansion valve. After the dryer is turned on, the dryer pre-operates at a low frequency, and the compressor operates according to the set lower limit frequency. The electronic expansion valve regulates the superheat in that when the superheat is higher than the target value after the pre-operation, the opening of the electronic expansion valve becomes larger, and when the superheat is lower than the target value, the opening of the electronic expansion valve decreases. When the superheat reaches a constant range, the electronic expansion valve stops regulating.

[0006] Preferably, the dew point temperature regulation is specifically that after pre-operation, when the dew point temperature is higher than the target value, the compressor frequency enters PID regulation, the upper and lower limit frequencies are increased in stages within a set range, and step-by-step regulation is performed, and the regulation time is set as needed; when the dew point temperature is lower than the target value, the compressor frequency enters PID regulation, the upper and lower limit frequencies are reduced in stages within a set range, and step-by-step regulation is performed, and the regulation time is set as needed; when the regulation time is over, the difference between the feedback value and the target value is greater than a constant range, which is equivalent to the dew point temperature being lower or higher than the target value, and therefore enters PID regulation again until the difference between the feedback value and the target value is lower than the constant range, at which time the frequency stops adjusting and the dryer works normally.

[0007] Preferably, the protection mechanism is specifically refrigerant pressure protection. When the refrigerant high pressure is higher than the set upper limit judgment value, the frequency is reduced to the set high pressure protection frequency, and the expansion valve opening is maintained at 100% until the high pressure is reduced to the set allowable value; when the refrigerant low pressure is lower than the set lower limit judgment value, the frequency is reduced to the lower limit frequency until the refrigerant low pressure returns to the set allowable value; when the refrigerant pressure is within the range, the dew point temperature adjustment is entered; when it is detected that the high pressure of the refrigerant system is too high or the low pressure is too low, the mechanism will automatically take measures to avoid possible failures or machine trips.

[0008] Preferably, when the low pressure of the refrigerant is lower than a safety threshold, the electronic expansion valve adjusts its opening to increase the flow of the refrigerant to raise the low pressure level.

[0009] Preferably, when the refrigerant high pressure exceeds a preset safety threshold, the electronic expansion valve adjusts its opening accordingly to reduce the amount of refrigerant entering the evaporator, thereby further reducing the high pressure.

[0010] Preferably, the protection control also includes load-no-load stage protection logic, specifically, when a load drop is detected, the control system will quickly reduce the operating frequency of the compressor and reduce the circulation volume of the refrigerant to avoid the refrigerant pressure being too low; at the same time, the electronic expansion valve will also adjust the opening accordingly to reduce the flow rate of the refrigerant.

[0011] Preferably, the protection control also includes no-load-load stage protection logic, specifically, when a load increase is detected, the control system will quickly increase the operating frequency of the compressor to increase the circulation volume of the refrigerant; the electronic expansion valve will also adjust the opening accordingly to increase the flow rate of the refrigerant to quickly reach the required dew point temperature.

[0012] In summary, the present application has the following beneficial technical effects: 1. In a low temperature environment, the electronic expansion valve can effectively avoid the occurrence of the "ice blockage" phenomenon, that is, by controlling the appropriate opening to prevent the refrigerant from overcooling in the evaporator to form ice crystals and block the pipeline. At the same time, in a high temperature environment, the electronic expansion valve can ensure sufficient refrigerant flow, thereby avoiding the problem of poor drying effect. In addition, the electronic expansion valve can also automatically adjust the opening according to the suction superheat, which can not only improve the overall efficiency of the system, but also effectively prevent the liquid refrigerant from directly entering the compressor in a low temperature environment, thereby protecting the compressor from damage. Under high load conditions, the electronic expansion valve can also realize precise throttling and pressure reduction functions to ensure the stable operation of the system and efficient drying effect. The combination of the electronic expansion valve and variable frequency drive technology makes the variable frequency cold dryer a highly reliable, high-performance and highly adaptable air drying solution;

[0013] 2. Through the refrigerant pressure protection method, the variable frequency dryer can dynamically balance the high and low pressures of the refrigerant system, stabilize the frequency and dew point of the compressed air, and ensure that the equipment remains within a safe working range under various operating conditions. This protection mechanism not only improves the reliability of the system, but also extends the service life of the equipment and reduces maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0015] Figure 1 is a logic diagram of the control system in this embodiment; DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The following is combined with Figure 1 This application is described in further detail.

[0018] A control system for a variable frequency refrigerated dryer is composed of the following three controls, namely, superheat adjustment, dew point temperature adjustment, and protection mechanism through an electronic expansion valve. After the dryer is turned on, the dryer pre-operates at a low frequency, and the compressor operates at a set lower limit frequency;

[0019] The electronic expansion valve regulates superheat in such a way that when the superheat is higher than the target value after pre-operation, the opening of the electronic expansion valve becomes larger; when the superheat is lower than the target value, the opening of the electronic expansion valve decreases; when the superheat reaches a constant range, the electronic expansion valve stops regulating at this time. The electronic expansion valve automatically adjusts the opening according to the suction superheat, which can not only improve the overall efficiency of the system, but also effectively prevent the liquid refrigerant from directly entering the compressor in a low-temperature environment, thereby protecting the compressor from damage;

[0020] The dew point temperature regulation is specifically that after pre-operation, when the dew point temperature is higher than the target value, the compressor frequency enters PID regulation, and the upper and lower limit frequencies increase in stages within the set range, and step-by-step regulation is performed, and the regulation time is set as needed; when the dew point temperature is lower than the target value, the compressor frequency enters PID regulation, and the upper and lower limit frequencies decrease in stages within the set range, and step-by-step regulation is performed, and the regulation time is set as needed; when the regulation time is over, the difference between the feedback value and the target value is greater than the constant range, which is equivalent to the dew point temperature being lower or higher than the target value, so it enters PID regulation again until the difference between the feedback value and the target value is lower than the constant range, at which time the frequency stops adjusting and the dryer works normally.

[0021] The protection mechanism is specifically refrigerant pressure protection. When the refrigerant high pressure is higher than the set upper limit judgment value, the frequency is reduced to the set high pressure protection frequency, and the expansion valve opening is maintained at 100% until the high pressure drops to the set allowable value; when the refrigerant low pressure is lower than the set lower limit judgment value, the frequency is reduced to the lower limit frequency until the refrigerant low pressure returns to the set allowable value; when the refrigerant pressure is within the range, the dew point temperature adjustment is entered; when it is detected that the high pressure of the refrigerant system is too high or the low pressure is too low, the mechanism will automatically take measures to avoid possible failures or tripping.

[0022] Specifically, when the high pressure exceeds the preset safety threshold, the control system automatically reduces the operating frequency of the compressor. This operation reduces the refrigerant flow generated by the compressor and helps alleviate the high pressure condition. At the same time, the electronic expansion valve will adjust its opening accordingly to reduce the amount of refrigerant entering the evaporator, thereby further reducing the high pressure. Conversely, when the low pressure is below the safety threshold, the control system will increase the operating frequency of the compressor to increase the circulation of the refrigerant. The electronic expansion valve will also adjust the opening to increase the flow of refrigerant to increase the low pressure level. In this way, the variable frequency cold dryer can dynamically balance the high and low pressures of the refrigerant system to ensure that the equipment remains in a safe operating range under various operating conditions. This protection mechanism not only improves the reliability of the system, but also extends the service life of the equipment and reduces maintenance costs.

[0023] Under high load conditions, the electronic expansion valve can also achieve precise throttling and pressure reduction functions to ensure stable operation of the system and efficient drying effect. The combination of electronic expansion valve and variable frequency drive technology makes the variable frequency cold dryer a highly reliable, superior performance and highly adaptable air drying solution.

[0024] During the load-to-no-load phase, the system may encounter the risk of low refrigerant pressure. To cope with this situation, the control system of the variable frequency dryer adds protection logic so that the frequency of the compressor can respond quickly to load changes: when a load drop is detected, the control system will quickly reduce the operating frequency of the compressor and reduce the circulation of the refrigerant to avoid low refrigerant pressure; at the same time, the electronic expansion valve will also adjust the opening accordingly to reduce the flow of the refrigerant to help maintain a suitable low pressure level; this fast response mechanism ensures that the dew point temperature remains stable even when the load drops rapidly, and avoids tripping caused by low refrigerant pressure.

[0025] When the system changes from no-load state to load state during the no-load-load phase, it needs to be adjusted quickly to reach the target dew point temperature. At this time, the control system of the variable frequency cold dryer will take the following measures: when the load increase is detected, the control system will quickly increase the operating frequency of the compressor to increase the circulation volume of the refrigerant; the electronic expansion valve will also adjust the opening accordingly to increase the flow of the refrigerant to quickly reach the required dew point temperature; this rapid response capability helps to shorten the time it takes for the system to reach a stable operating state and ensure that the dew point temperature can be adjusted to the target value in a timely manner. Through the above-mentioned load adaptive function, the variable frequency cold dryer can better adapt to different working conditions, ensure that the system can still maintain a stable operating state when the load changes, and improve the reliability and efficiency of the entire system.

[0026] In the description of the present invention, it is necessary to understand that the terms "coaxial", "bottom", "one end", "top", "middle", "the other end", "upper", "one side", "top", "inside", "front", "center", "both ends" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0027] In the present invention, unless otherwise clearly stipulated and limited, the terms such as "installation", "setting", "connection", "fixation" and "screw-on" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to the specific circumstances.

[0028] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A control system for a variable frequency refrigerated dryer. Features: It consists of the following three controls: superheat regulation, dew point temperature regulation, and protection mechanism through the electronic expansion valve. After the dryer is turned on, the dryer pre-operates at a low frequency, and the compressor operates at the set lower limit frequency. The electronic expansion valve regulates the superheat in that when the superheat is higher than the target value after the pre-operation, the opening of the electronic expansion valve becomes larger. When the superheat is lower than the target value, the opening of the electronic expansion valve decreases. When the superheat reaches a constant range, the electronic expansion valve stops regulating.

2. A control system for a variable frequency refrigerated dryer according to claim 1, Features: The dew point temperature regulation is specifically that after pre-operation, when the dew point temperature is higher than the target value, the compressor frequency enters PID regulation, and the upper and lower limit frequencies increase in stages within the set range, and step-by-step regulation is performed, and the regulation time is set as needed; when the dew point temperature is lower than the target value, the compressor frequency enters PID regulation, and the upper and lower limit frequencies decrease in stages within the set range, and step-by-step regulation is performed, and the regulation time is set as needed; when the regulation time is over, the difference between the feedback value and the target value is greater than the constant range, which is equivalent to the dew point temperature being lower or higher than the target value, so it enters PID regulation again until the difference between the feedback value and the target value is lower than the constant range, at which time the frequency stops adjusting and the dryer works normally.

3. A control system for a variable frequency refrigerated dryer according to claim 2, Features: The protection mechanism is specifically refrigerant pressure protection. When the refrigerant high pressure is higher than the set upper limit judgment value, the frequency is reduced to the set high pressure protection frequency, and the expansion valve opening is maintained at 100% until the high pressure drops to the set allowable value; when the refrigerant low pressure is lower than the set lower limit judgment value, the frequency is reduced to the lower limit frequency until the refrigerant low pressure returns to the set allowable value; when the refrigerant pressure is within the range, the dew point temperature adjustment is entered; when it is detected that the high pressure of the refrigerant system is too high or the low pressure is too low, the mechanism will automatically take measures to avoid possible failures or tripping.

4. A control system for a variable frequency refrigerated dryer according to claim 3, Features: When the refrigerant low pressure is lower than the safety threshold, the electronic expansion valve adjusts its opening to increase the flow of refrigerant to raise the low pressure level.

5. The control system of a variable frequency refrigerated dryer according to claim 3, Features: When the refrigerant high pressure exceeds the preset safety threshold, the electronic expansion valve adjusts its opening accordingly to reduce the amount of refrigerant entering the evaporator, thereby further reducing the high pressure.

6. A control system for a variable frequency refrigerated dryer according to claim 3, Features: The protection control also includes load-no-load stage protection logic. Specifically, when a load drop is detected, the control system will quickly reduce the operating frequency of the compressor and reduce the circulation volume of the refrigerant to avoid the refrigerant pressure being too low. At the same time, the electronic expansion valve will also adjust the opening accordingly to reduce the flow of the refrigerant.

7. The control system of a variable frequency refrigerated dryer according to claim 3, Features: The protection control also includes no-load-load stage protection logic. Specifically, when an increase in load is detected, the control system will quickly increase the operating frequency of the compressor to increase the circulation volume of the refrigerant; the electronic expansion valve will also adjust the opening accordingly to increase the flow rate of the refrigerant to quickly reach the required dew point temperature.

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