A protection method for preventing excessive high pressure of a compressor

Abstract

The application discloses a protection method for preventing high pressure of a compressor from being too high, which comprises the following steps of S1, detecting a variable frequency input actual current CT1 after the compressor is started and judging whether CT1 is greater than A; if yes, the step S2 is performed; otherwise, the compressor is normally operated; S2, continuously updating an upper limit value Np of the compressor protection control revolution; continuously judging whether CT1 is greater than A; if yes, the step S3 is performed; otherwise, the step S4 is performed; S3, judging whether CT1 is greater than or equal to A+t and whether the time has lasted for 3 seconds; if yes, the compressor is stopped for protection; otherwise, the compressor is normally operated; S4, judging whether B<CT1<A; if yes, the upper limit value Np of the compressor revolution is not changed, and the frequency operation is maintained; otherwise, the step S5 is performed; S5, judging whether CT1 is less than B; if yes, the protection control is released; otherwise, the step S2 is returned. The protection is stopped when the high pressure is too high or the high pressure is out of range, and the reliability of the compressor is ensured without increasing the cost.

Description

Technical Field

[0001] This invention belongs to the field of air conditioning technology, specifically relating to a protection method for preventing excessively high pressure in a compressor. Background Technology

[0002] Most air conditioners on the market currently use pressure controllers to control the compressor's operating pressure or prevent overpressure-induced shutdown. Pressure controllers are mainly divided into two types: pressure sensors and pressure switches. A pressure sensor is a device used to control fluid pressure. Its working principle is to sense fluid pressure, convert it into an electrical signal, and then process it through a computer chip. Based on the pressure detection results, it performs precise pressure regulation and control on the air conditioner's components. A pressure switch is a mechanical control device that detects pressure transmission. When the compressor's discharge pressure in the air conditioner reaches or exceeds the maximum set value, the pressure switch's electrical contacts cut off the control signal power, causing the compressor to stop working, thus providing protection and automatic control. While using pressure sensors or mechanical controls can indeed achieve the purpose of pressure control, it increases hardware costs, especially since pressure sensors are relatively expensive. Furthermore, pressure switches or pressure sensors are welded to the pipeline; when the pressure is too high, the stress can easily cause the pipes to crack and leak. Summary of the Invention

[0003] To address the issues raised in the background section regarding the high cost and susceptibility to pipe cracking and leakage associated with pressure sensors or pressure switches, this invention provides a protection method to prevent excessively high pressure in compressors.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a protection method for preventing excessive high pressure of a compressor, the method comprising: S1, after the compressor is turned on, detecting the actual variable frequency input current CT1 and determining whether CT1 is greater than A, where A is a given rated current value, used as a protection standard value; if yes, proceed to step S2; otherwise, the compressor operates normally.

[0005] S2. Continuously update the upper limit value Np of the press protection control speed, Np = Na, where N is the current actual speed of the press, a is a constant value for the change of the press speed each time it is executed, and the minimum value of Np is the lower limit value of the press speed; continue to determine whether CT1 is greater than A. If yes, go to step S3; otherwise, go to step S1.

[0006] S3. Determine whether CT1 is greater than or equal to A+t and has lasted for 3 seconds. If yes, the compressor will stop protection; otherwise, proceed to step S4. t is the upper limit of the frequency converter input current deviation.

[0007] S4. Determine whether B < CT1 < A. B is the protection termination value. If yes, the compressor speed limit Np will no longer change and the frequency will be maintained. Otherwise, proceed to step S5.

[0008] S5. Determine if CT1 < B. If yes, release the protection control; otherwise, return to step S2.

[0009] Preferably, the protection standard value A is calculated as follows:

[0010] During cooling, A 冷 =K1*(Th O-A –T 冷房标准 )+A 冷房额定 ;

[0011] When heating, A 热 =K2*(Th O-A –T 暖房标准 )+A 暖房额定 ;

[0012] Where K1 is the constant coefficient for cooling room operation, K2 is the constant coefficient for heating room operation, and Th O-A The outdoor temperature value, T 冷房标准 T is the temperature value specified for standard refrigeration operating conditions. 暖房标准 A is the temperature value specified for the standard heating condition. 冷房额定 The compressor current protection value specified by the national standard for cold room operation at an outdoor temperature of 35℃ is A. 暖房额定 The compressor current protection value is specified by national standards when the outdoor temperature is 7℃ during greenhouse operation.

[0013] Preferably, the sampling time of the variable frequency input current CT1 is 3 seconds.

[0014] Preferably, if the compressor cycles more than 5 times within 1 hour of stopping and resuming, a high-pressure protection alarm will be triggered.

[0015] Compared with the prior art, the beneficial effects of the present invention are:

[0016] This invention is based on the fact that the compressor's variable frequency input current and the high pressure of the compressor load are basically linearly related. The AC input current value under different operating loads is used as an indirect signal parameter to detect whether the pressure is too high or out of range. The compressor frequency is directly adjusted according to the current value to prevent the compressor from shutting down when the pressure is too high or out of range. This invention replaces pressure switches or pressure sensors and ensures the reliability of the compressor without increasing costs. Attached Figure Description

[0017] Figure 1 A flowchart illustrating a protection method to prevent excessively high pressure in the compressor.

[0018] Figure 2 This is a curve showing the relationship between outdoor ambient temperature, compressor high pressure, and inverter input current. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example

[0021] Please see Figure 1-2 The present invention provides the following technical solution: a protection method for preventing excessively high pressure in a compressor, the method comprising:

[0022] S1. After the compressor is turned on, the actual variable frequency input current CT1 is detected and it is determined whether CT1 is greater than A, where A is the given rated current value, which is used as the protection standard value. If it is, proceed to step S2; otherwise, the compressor operates normally. The sampling time of the variable frequency input current CT1 is 3 seconds.

[0023] S2. Continuously update the upper limit value Np of the press protection control speed, Np = Na, where N is the current actual speed of the press, a is a constant value for the change of the press speed each time it is executed, and the minimum value of Np is the lower limit value of the press speed; continue to determine whether CT1 is greater than A. If yes, go to step S3; otherwise, go to step S1.

[0024] S3. Determine whether CT1 is greater than or equal to A+t and has lasted for 3 seconds. If yes, the compressor will stop protection; otherwise, proceed to step S4. t is the upper limit of the frequency converter input current deviation.

[0025] S4. Determine whether B < CT1 < A. B is the protection termination value. If yes, the compressor speed limit Np will no longer change and the frequency will be maintained. Otherwise, proceed to step S5.

[0026] S5. Determine if CT1 < B. If yes, release the protection control; otherwise, return to step S2.

[0027] The protection standard value A is calculated as follows:

[0028] During cooling, A 冷 =K1*(Th O-A –T 冷房标准 )+A 冷房额定 ;

[0029] When heating, A 热 =K2*(Th O-A –T 暖房标准 )+A 暖房额定 ;

[0030] Where K1 is the constant coefficient for cooling room operation, K2 is the constant coefficient for heating room operation, and Th O-AThe outdoor temperature value, T 冷房标准 T is the temperature value specified for standard refrigeration operating conditions. 暖房标准 A is the temperature value specified for the standard heating condition. 冷房额定 The compressor current protection value specified by the national standard for cold room operation at an outdoor temperature of 35℃ is A. 暖房额定 This is the compressor current protection value specified by national standards when the outdoor temperature is 7℃ during greenhouse operation. If the compressor cycles through shutdown and recovery more than 5 times within 1 hour, a high-pressure protection alarm will be triggered.

[0031] The principle of this embodiment is based on the fact that the compressor's variable frequency input current and the high-pressure of the compressor load are basically linearly related. Frequency control is achieved by assigning different current values ​​to different operating conditions corresponding to the high-pressure values, preventing excessively high pressure or pressure exceeding the range and thus protecting the compressor from shutdown. This replaces pressure switches or pressure sensors, ensuring compressor reliability without increasing costs. Figure 2 As shown, Figure 2 The diagram shows the relationship between the high pressure, outdoor ambient temperature, and inverter input current during cooling for a particular model. The blue line represents the relationship between the inverter input current and the compressor load pressure, while the red line represents the relationship between the outdoor ambient temperature and the compressor load pressure. Both lines exhibit a roughly linear relationship.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A protection method for preventing excessive high pressure in a compressor, characterized by, The method is: S1, after the opening of the press, detecting the variable frequency input actual current CT1 and judging whether CT1 is greater than A, A is a given rated current value, as a protection standard value, yes to step S2, otherwise the press runs normally; S2, continuously updating the press protection control upper limit value Np, Np=N-a, N is the current actual number of the press, a is a constant value of the press number of times of execution change, the minimum value of Np is the lower limit value of the press number of times; continue to judge whether CT1 is greater than A, yes to step S3, otherwise to step S1; S3, judging whether CT1 is greater than or equal to A+t and lasts for 3 seconds, yes to the press shutdown protection, otherwise to step S4, t is the variable frequency input current deviation upper limit; S4, judging whether B<CT1<A, B is the protection end release value, yes to the compressor upper limit value Np no longer changes, keep frequency operation, otherwise to step S5; S5, judging whether CT1<B, yes to release protection control, otherwise return to step S2; The calculation of the protection standard value A is as follows: During cooling, A 冷 =K1×(Th O-A –T 冷房标准 )+A 冷房额定 ; When heating, A 热 = K2 x (Th O-A – T 暖房标准 ) + A 暖房额定 ; Wherein, K1 is the cooling condition constant, K2 is the heating condition constant, Th O-A is the outdoor temperature value, T 冷房标准 is the temperature value stipulated by the refrigeration standard condition, T 暖房标准 is the temperature value stipulated by the heating standard condition, A 冷房额定 is the compressor current protection value stipulated by the national standard for the cooling condition when the outdoor temperature is 35℃, A 暖房额定 is the compressor current protection value stipulated by the national standard for the heating condition when the outdoor temperature is 7℃.

2. The method of claim 1, wherein the method further comprises: The sampling time of the variable frequency input current CT1 is 3 seconds.

3. The method of claim 1, wherein the step of determining the high pressure condition of the compressor is performed by determining a pressure differential between the high pressure and the low pressure. When the compressor stops-recovery within 1 hour, the cycle is more than 5 times, high pressure protection alarm is carried out.

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