Protection method for preventing high pressure of compressor from being too high

Abstract

The invention discloses a protection method for preventing the high pressure of a compressor from being too high, and the method comprises the steps: S1, detecting the actual variable-frequency input current CT1 after a press is started, judging whether the CT1 is greater than A or not, if yes, turning to S2, and otherwise, enabling the press to operate normally; s2, continuously updating the upper limit value Np of the protection control revolution number of the press; continuing to judge whether CT1 is greater than A, if yes, turning to S3, and otherwise, turning to S4; s3, judging whether CT1 is greater than or equal to A + t and lasts for 3 seconds, if yes, stopping the press for protection, and if not, normally operating the press; s4, whether B < CT1 < A or not is judged, B is a protection end relieving value, if yes, the upper limit value Np of the revolution number of the compressor does not change any more, frequency operation is kept, and if not, the step S5 is executed; and S5, judging whether CT1 is less than B or not, if yes, releasing protection control, and otherwise, returning to S2. Protection shutdown when the high voltage is too high or the high voltage exceeds the range is prevented, and the reliability of the press is ensured on the premise that the cost is not increased.

Description

Technical Field

[0001] The invention belongs to the technical field of air conditioning, and in particular relates to a protection method for preventing the high pressure of a compressor from being too high. Background Art

[0002] At present, most air conditioners on the market use pressure controllers to control the operating pressure of the compressor or prevent shutdown protection due to excessive pressure. 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 perform microprocessing through a computer chip to finely adjust the pressure of the air conditioner components according to the results of the pressure detection. A pressure switch is a mechanical control device that detects pressure conduction. That is, when the discharge pressure of the compressor in the air conditioner reaches and exceeds the maximum set value, the electrical contacts of the pressure switch will cut off the control signal power supply, causing the compressor to stop working, playing a role in protection and automatic control. The use of pressure sensors or mechanical control can indeed achieve the purpose of pressure control, but it requires an increase in hardware costs, especially the high cost of pressure sensors. In addition, when the pressure switch or pressure sensor is welded on the pipeline, when the pressure is too high, the pipe is prone to cracking and leakage due to high stress. Summary of the invention

[0003] In order to solve the problems in the above background technology that the use of pressure sensors or pressure switches is high in cost and prone to pipe cracking and leakage, the present invention provides a protection method for preventing the high pressure of a compressor from being too high.

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

[0005] S2, continuously update the upper limit value Np of the compressor protection control speed, Np = Na, N is the current actual speed of the compressor, a is the constant value of the compressor speed change each time, and the minimum value of Np is the lower limit value of the compressor speed; continue to judge 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 lasts for 3 seconds, if yes, the compressor will shut down for protection, otherwise go to step S4, t is the upper limit of the frequency conversion input current deviation;

[0007] S4, judging whether B<CT1<A, B is the protection end release value, if so, the compressor speed upper limit value Np does not change, and the frequency operation is maintained, otherwise, go to step S5;

[0008] S5. Determine whether 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] Among them, K1 is the constant coefficient of cooling room condition, K2 is the constant coefficient of heating room condition, Th O-A is the outdoor temperature, T 冷房标准 The temperature value specified for the refrigeration standard working condition, T 暖房标准 A is the temperature value specified for the standard heating condition. 冷房额定 The current protection value of the compressor when the temperature is 35℃ outdoors in the cold room condition as specified by the national standard, A 暖房额定 The national standard stipulates the compressor current protection value at 7°C outdoors in a greenhouse condition.

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

[0014] Preferably, when the compressor is shut down and resumed for more than 5 times within 1 hour, a high pressure protection alarm is issued.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention is based on the basically linear relationship between the variable frequency input current of the compressor and the high pressure of the compressor load. The AC input current value under different working loads is used as an indirect signal parameter for detecting whether the pressure is too high or out of range. The compressor frequency is directly adjusted according to the current value to prevent protection shutdown when the high pressure is too high or out of range, and replace the pressure switch or pressure sensor to ensure the reliability of the compressor without increasing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Flow chart of the protection method to prevent the compressor high pressure from being too high.

[0018] Figure 2 This is the relationship curve between outdoor ambient temperature, compressor high pressure, and variable frequency input current. DETAILED DESCRIPTION

[0019] 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.

[0020] Example

[0021] See also Figure 1-2 The present invention provides the following technical solution: a protection method for preventing the high pressure of a compressor from being too high, the method comprising:

[0022] S1. After the compressor is turned on, detect the actual variable frequency input current CT1 and determine whether CT1 is greater than A, where A is a given rated current value as a protection standard value. If yes, go 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 compressor protection control speed, Np = Na, N is the current actual speed of the compressor, a is the constant value of the compressor speed change each time, and the minimum value of Np is the lower limit value of the compressor speed; continue to judge 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 lasts for 3 seconds, if yes, the compressor will shut down for protection, otherwise go to step S4, t is the upper limit of the frequency conversion input current deviation;

[0025] S4, judging whether B<CT1<A, B is the protection end release value, if so, the compressor speed upper limit value Np does not change, and the frequency operation is maintained, otherwise, go to step S5;

[0026] S5. Determine whether 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] Among them, K1 is the constant coefficient of cooling room condition, K2 is the constant coefficient of heating room condition, Th O-Ais the outdoor temperature, T 冷房标准 The temperature value specified for the standard refrigeration condition, T 暖房标准 A is the temperature value specified for the standard heating condition. 冷房额定 The current protection value of the compressor when the temperature is 35℃ outdoors in the cold room condition as specified by the national standard, A 暖房额定 The national standard specifies the compressor current protection value at 7°C in a warm room. When the compressor stops and resumes for more than 5 times within 1 hour, a high-voltage protection alarm is issued.

[0031] The principle of the method of this embodiment is based on the linear relationship between the variable frequency input current of the compressor and the high pressure of the compressor load. The frequency is controlled by assigning different current values ​​corresponding to the high pressure values ​​under various working conditions to prevent the high pressure from being too high or the high pressure from exceeding the range. It replaces the pressure switch or pressure sensor and ensures the reliability of the compressor without increasing the cost. Figure 2 As shown, Figure 2 The figure shows the relationship between the high pressure, outdoor ambient temperature and variable frequency input current of a model during cooling. The blue line is the relationship curve between the variable frequency input current and the compressor load pressure, and the red line is the relationship curve between the outdoor ambient temperature and the compressor load pressure, both of which are roughly linear.

[0032] 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 method for protecting a compressor from excessive high pressure, characterized in that: The method is: S1. After the compressor is turned on, detect the actual frequency conversion input current CT1 and determine whether CT1 is greater than A. A is a given rated current value, which is used as the protection standard value. If yes, go to step S2, otherwise the compressor operates normally. S2, continuously update the upper limit value Np of the compressor protection control speed, Np = Na, N is the current actual speed of the compressor, a is the constant value of the compressor speed change each time, and the minimum value of Np is the lower limit value of the compressor speed; continue to judge whether CT1 is greater than A, if yes, go to step S3, otherwise go to step S1; S3, determine whether CT1 is greater than or equal to A+t and lasts for 3 seconds, if yes, the compressor will shut down for protection, otherwise go to step S4, t is the upper limit of the frequency conversion input current deviation; S4, judging whether B<CT1<A, B is the protection end release value, if so, the compressor speed upper limit value Np does not change, and the frequency operation is maintained, otherwise, go to step S5; S5. Determine whether CT1<B. If yes, release the protection control. Otherwise, return to step S2.

2. The method for protecting a compressor from excessive high pressure according to claim 1, characterized in that: The protection standard value A is calculated 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*(Th O-A –T 暖房标准 )+A 暖房额定 ; Among them, K1 is the constant coefficient of cooling room condition, K2 is the constant coefficient of heating room condition, Th O-A is the outdoor temperature, T 冷房标准 The temperature value specified for the standard refrigeration condition, T 暖房标准 A is the temperature value specified for the standard heating condition. 冷房额定 The current protection value of the compressor when the temperature is 35℃ outdoors in the cold room condition as specified by the national standard, A 暖房额定 The national standard stipulates the compressor current protection value at 7°C outdoors in a greenhouse condition.

3. The method for protecting a compressor from excessive high pressure according to claim 1, characterized in that: The sampling time of the variable frequency input current CT1 is 3 seconds.

4. The method for protecting a compressor from excessive high pressure according to claim 1, characterized in that: When the compressor stops and resumes for more than 5 times within 1 hour, a high pressure protection alarm will be issued.

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