Condensing unit direct current motor speed control system based on pressure detection

Abstract

This invention provides a DC motor speed control system for a condensing unit based on pressure detection, including a condenser, a compressor, a high-pressure sensor, an ambient temperature sensor, and a control device. The high-pressure sensor detects the pressure in the high-pressure pipe of the condenser according to a preset cycle and sends the detected high-pressure value to the control device. The control device adjusts the speed of the DC motor based on the high-pressure value. The control system provided by this invention, by detecting the high-pressure of the condenser, adjusts the fan speed in real time according to the current operating pressure of the condenser, thereby maintaining the condenser in a normal operating environment. This overcomes the problem of misjudging the condenser's heat dissipation needs under low-temperature operating conditions and avoids frequent triggering of high-pressure switches or low-pressure protection by the condensing unit.

Description

Technical Field

[0001] This invention relates to the field of automation equipment technology, specifically to a DC motor speed control system for condensing units based on pressure detection. Background Technology

[0002] Condensing chillers are commonly used refrigeration equipment in places such as cold storage, convenience stores, and supermarkets. The indoor units they are connected to are usually air coolers or freezers. Due to the requirements of the application scenarios, condensing chillers are generally required to run continuously throughout the year and have a wide operating temperature range, requiring stable operation from -30℃ to 48℃. In order to ensure the continuous operation of condensing chillers, a cooling motor is usually installed as a heat dissipation device to maintain the normal working environment of the condensing chiller.

[0003] Traditional cooling motors are generally AC motors. However, due to their structure and principle, AC motors usually only have one speed setting and are difficult to adjust. That is, the cooling motor can only be turned on or off and cannot be adjusted appropriately according to the working conditions of the condenser and the surrounding environment.

[0004] Therefore, a solution is needed to adjust the speed of the cooling motor, such as the utility model patent with application number 202122198482.4, which discloses a DC motor control structure in a condensing unit. It adopts a combination of temperature sensor and DC motor to realize the speed adjustment function of the cooling fan of the condensing unit according to the exhaust temperature of the condensing unit, so as to meet the cooling needs of the condensing unit under different conditions.

[0005] However, since the temperature of cold storage or freezer is generally maintained below 0°C, the exhaust temperature of the condensing unit is not high, which makes it impossible for the temperature sensor to determine the current heat dissipation demand of the condensing unit. As a result, the DC motor does not start, which in turn leads to excessively high pressure of the condensing unit, triggering the high-pressure switch or low-pressure protection. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a DC motor speed control system for condensing units based on pressure detection. This system avoids the problem of cooling fans failing to start due to external ambient temperature. By detecting the actual operating pressure of the condensing unit, the speed of the DC motor is adjusted in real time to ensure that the condensing unit remains in a normal operating environment.

[0007] This invention provides a DC motor speed control system for a condensing unit based on pressure detection, including a condenser 100, a compressor 200, a high-pressure sensor 300, an ambient temperature sensor 400, and a control device;

[0008] The condenser 100 is provided with an exhaust pipe and at least one DC motor 110;

[0009] The control device includes a switching power supply module 540 and at least one motor drive board 550.

[0010] The DC motor 110 is connected to the output terminal of the motor drive board 550, and the power supply terminal of the motor drive board 550 is connected to the switching power supply module 540.

[0011] The high-pressure sensor 300 is installed at the high-pressure pipe of the condenser 100, and the output terminal of the high-pressure sensor 300 is connected to the input terminal of the control device; the ambient temperature sensor 400 is installed outside the condenser 100, and the output terminal of the ambient temperature sensor 400 is connected to the input terminal of the control device.

[0012] The high-pressure sensor 300 is used to detect the pressure in the high-pressure pipeline of the condenser 100 according to a preset cycle, and send the detected high-pressure value to the control device.

[0013] The ambient temperature sensor 400 is used to detect the temperature of the environment in which the condenser 100 is located, and to send the detected ambient temperature to the control device;

[0014] The control device is used to generate the initial speed of the DC motor 110 based on the ambient temperature;

[0015] When the high pressure value is not less than the preset pressure value, the control device is used to control the DC motor 110 to rotate at the initial speed;

[0016] The control device is also used to control the speed of the DC motor (110) based on the changing trend and pressure value of two consecutive received high pressure values.

[0017] In one embodiment of the present invention, when two consecutive high pressure values ​​received by the control device show an upward trend, and the latest received high pressure value is in the first pressure range, the control device is further used to control the speed of the DC motor 110 to increase by a first preset speed value.

[0018] When the control device receives two consecutive high pressure values ​​that show an upward trend, and the latest received high pressure value exceeds the upper limit of the first pressure range, the control device is also used to control the speed of the DC motor 110 to increase by a second preset speed value.

[0019] When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest received high pressure value is in the second pressure range, the control device is also used to control the speed of the DC motor 110 to decrease by a second preset speed value.

[0020] When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest received high pressure value is in the third pressure range, the control device is also used to control the speed of the DC motor 110 to decrease by a first preset speed value.

[0021] When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest received high pressure value exceeds the lower limit of the third pressure range, the control device is also used to control the speed of the DC motor 110 to decrease by a third preset speed value.

[0022] When the current speed of the DC motor 110 is less than the preset minimum speed, and the high pressure value received by the control device exceeds the lower limit of the third pressure range, the control device is also used to control the DC motor 110 to stop rotating.

[0023] In one embodiment of the present invention, the control device further includes an AC contactor 510, a compressor terminal 520, and a power input terminal 530;

[0024] The compressor 200 is connected to one end of the AC contactor 510 via the compressor terminal 520, and the other end of the AC contactor 510 is connected to the power input terminal 530.

[0025] In one embodiment of the present invention, the DC motor speed control system for a condensing unit based on pressure detection further includes an exhaust temperature sensor 600.

[0026] The detection end of the exhaust temperature sensor 600 is connected to the exhaust pipe, and the output end of the exhaust temperature sensor 600 is connected to the control device.

[0027] The exhaust temperature sensor 600 is used to detect the temperature of the exhaust port of the condenser 100 and send the detected exhaust temperature to the control device.

[0028] The control device is also used to control the DC motor 110 to rotate at the initial speed when the exhaust temperature is not less than the preset temperature and the high pressure value is less than the preset pressure value.

[0029] In one embodiment of the present invention, the DC motor speed control system for a condensing unit based on pressure detection further includes a display device 700.

[0030] The display device 700 is mounted on the control device;

[0031] The control device is also used to control the display device 700 to display the operating status of the compressor 200 and / or the condenser 100.

[0032] In one embodiment of the present invention, the DC motor speed control system for a condensing unit based on pressure detection further includes an electric heating belt 800.

[0033] The electric heating belt 800 is disposed at the bottom of the compressor 200; the control end of the electric heating belt 800 is connected to the control device;

[0034] The control device is also used to control the working state of the electric heating belt 800.

[0035] In one embodiment of the present invention, the DC motor speed control system for a condensing unit based on pressure detection further includes a liquid injection solenoid valve 900.

[0036] The liquid injection solenoid valve 900 is installed in the refrigerant pipeline connected to the compressor 200, and the control terminal of the liquid injection solenoid valve 900 is connected to the control device.

[0037] The control device is also used to control the working state of the liquid injection solenoid valve 900.

[0038] In one embodiment of the present invention, the DC motor speed control system for a condensing unit based on pressure detection further includes a bypass solenoid valve 1000.

[0039] One end of the bypass solenoid valve 1000 is connected to the intake pipe of the compressor 200, and the other end of the bypass solenoid valve 1000 is connected to the exhaust pipe of the compressor 200.

[0040] The control device is also used to control the bypass solenoid valve 1000 to open before starting the compressor 200;

[0041] The control device is also used to control the bypass solenoid valve 1000 to close after the bypass solenoid valve 1000 has been open for a period of not less than a preset time, and to control the compressor 200 to start.

[0042] In one embodiment of the present invention, the DC motor speed control system for a condensing unit based on pressure detection further includes a first pressure sensor and a second pressure sensor.

[0043] The first pressure sensor is disposed in the intake pipe of the compressor 200, and the second pressure sensor is disposed in the exhaust pipe of the compressor 200.

[0044] The output terminals of the first pressure sensor and the second pressure sensor are respectively connected to the input terminal of the control device;

[0045] The first pressure sensor is used to detect the intake pressure at the intake port of the compressor 200 and send it to the control device;

[0046] The second pressure sensor is used to detect the exhaust pressure at the exhaust port of the compressor 200 and send it to the control device;

[0047] The control device is also used to control the bypass solenoid valve 1000 to open when the received exhaust pressure is greater than the preset start pressure before the compressor 200 starts.

[0048] After the bypass solenoid valve 1000 is opened, when the intake pressure and exhaust pressure received by the control device are balanced, the control device is also used to control the bypass solenoid valve 1000 to close and control the compressor 200 to start.

[0049] The beneficial effects of this invention are:

[0050] The present invention provides a DC motor speed control system for condenser units based on pressure detection. By detecting the high pressure of the condenser, the speed of the fan is adjusted in real time according to the current working pressure of the condenser, thereby maintaining the condenser in a normal working environment. This overcomes the problem of misjudging the heat dissipation demand of the condenser under low temperature working conditions and avoids the condenser unit from frequently triggering the high-pressure switch or low-pressure protection. Attached Figure Description

[0051] Figure 1 This is a circuit diagram of a DC motor speed control system for a condensing unit based on pressure detection, as described in one embodiment of the present invention.

[0052] Figure 2 This is a connection structure diagram of a condenser unit according to an embodiment of the present invention;

[0053] Figure 3 This is a schematic diagram illustrating the relationship between the high-pressure value of the condenser and the speed of the DC motor in one embodiment of the present invention.

[0054] Explanation of reference numerals in the attached drawings: condenser 100, DC motor 110, compressor 200, high pressure sensor 300, ambient temperature sensor 400, AC contactor 510, compressor terminal 520, power input terminal 530, switching power supply module 540, motor drive board 550, common neutral wire terminal 560, exhaust temperature sensor 600, display device 700, electric heating belt 800, liquid injection solenoid valve 900, bypass solenoid valve 1000. Detailed Implementation

[0055] It should be noted that in this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0056] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0057] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0058] like Figure 1-2 As shown, in one embodiment of the present invention, a DC motor speed control system for a condensing unit based on pressure detection is provided, including a condenser 100, a compressor 200, a high-pressure sensor 300, an ambient temperature sensor 400, and a control device.

[0059] The condenser 100 is provided with an exhaust pipe and at least one DC motor 110;

[0060] The control device includes an AC contactor 510, a compressor terminal 520, a power input terminal 530, a switching power supply module 540, and at least one motor drive board 550.

[0061] The compressor 200 is connected to one end of the AC contactor 510 via the compressor terminal 520, and the other end of the AC contactor 510 is connected to the power input terminal 530; the DC motor 110 is connected to the output terminal of the motor drive board 550, and the power supply terminal of the motor drive board 550 is connected to the switching power supply module 540.

[0062] The high-pressure sensor 300 is installed at the high-pressure pipe of the condenser 100, and the output terminal of the high-pressure sensor 300 is connected to the input terminal of the control device; the ambient temperature sensor 400 is installed outside the condenser 100, and the output terminal of the ambient temperature sensor 400 is connected to the input terminal of the control device.

[0063] The high-pressure sensor 300 is used to detect the pressure in the high-pressure pipeline of the condenser 100 according to a preset cycle, and send the detected high-pressure value to the control device.

[0064] The ambient temperature sensor 400 is used to detect the temperature of the environment in which the condenser 100 is located, and to send the detected ambient temperature to the control device;

[0065] The control device is used to generate the initial speed of the DC motor 110 based on the ambient temperature;

[0066] When the high pressure value is not less than the preset pressure value, the control device is used to control the DC motor 110 to rotate at the initial speed;

[0067] When the control device receives two consecutive high pressure values ​​that show an upward trend, and the latest received high pressure value is within the first pressure range, the control device is also used to control the speed of the DC motor 110 to increase by a first preset speed value.

[0068] When the control device receives two consecutive high pressure values ​​that show an upward trend, and the latest received high pressure value exceeds the upper limit of the first pressure range, the control device is also used to control the speed of the DC motor 110 to increase by a second preset speed value.

[0069] When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest received high pressure value is in the second pressure range, the control device is also used to control the speed of the DC motor 110 to decrease by a second preset speed value.

[0070] When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest received high pressure value is in the third pressure range, the control device is also used to control the speed of the DC motor 110 to decrease by a first preset speed value.

[0071] When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest received high pressure value exceeds the lower limit of the third pressure range, the control device is also used to control the speed of the DC motor 110 to decrease by a third preset speed value.

[0072] When the current speed of the DC motor 110 is less than the preset minimum speed, and the high pressure value received by the control device exceeds the lower limit of the third pressure range, the control device is also used to control the DC motor 110 to stop rotating.

[0073] Specifically, in a specific application scenario of this invention, such as Figure 3 As shown, the initial speed calculation formula of the DC motor is: S0 = min(T / 30*800, 800) RPM; where S0 is the initial speed and T is the ambient temperature; for example, when the ambient temperature of the condenser is 25℃, the initial speed of the DC motor S0 = min(25 / 30*800, 800) = 666 RPM, that is, the initial speed of the DC motor 110 is 666 revolutions per minute;

[0074] Let the preset pressure value be 'a', the first pressure range be [c, e], the second pressure range be (d, f], and the third pressure range be (b, d]. The preset pressure value 'a' ranges from 0.8 to 1.0 MPa; the lower limit of the first pressure range 'c' ranges from 1.0 to 1.2 MPa; the upper limit of the first pressure range 'e' ranges from 1.2 to 1.4 MPa; the lower limit of the second pressure range 'd' ranges from 0.9 to 1.2 MPa; the upper limit of the second pressure range 'f' ranges from 1.1 to 1.3 MPa; and the lower limit of the third pressure range 'b' ranges from 0.7 to 0.9 MPa. Those skilled in the art can set corresponding preset pressure values ​​and pressure ranges according to the actual needs of condensing units with different signals.

[0075] The first preset speed value is 20-50 RPM, the second preset speed value is 30-80 RPM, and the third preset speed value is 10-30 RPM. Those skilled in the art can set the corresponding speed value according to the selected DC motor model.

[0076] In a preferred embodiment of the present invention, the preset pressure value is 0.9 MPa, and the first pressure range is...

[0077] The pressure range is [1.1MPa, 1.3MPa], the second pressure range is (1.0MPa, 1.2MPa], and the third pressure range is (0.8MPa, 1.0MPa]; the first preset speed is 20RPM, the second preset speed is 40RPM, and the third preset speed is 10RPM.

[0078] The high-pressure sensor 300 detects the pressure in the high-pressure pipeline of the condenser 100 every 10 seconds. When the control device receives a high-pressure reading of not less than 0.9 MPa from the high-pressure sensor 300, and the ambient temperature is 25°C, the control device controls the DC motor 110 to start rotating at a speed of 666 RPM. When the control device receives two consecutive high-pressure values ​​of 1.0 MPa and 1.1 MPa, respectively, the control device determines that the high-pressure value is trending upward and that the latest received high-pressure value is within the first pressure range. Therefore, the control device controls the DC motor speed to increase by 20 RPM based on the current speed.

[0079] When the control device receives two consecutive high pressure values ​​of 1.2MPa and 1.4MPa, the control device determines that the high pressure value is on an upward trend and the latest received high pressure value exceeds the upper limit of the first pressure range. Therefore, the control device controls the DC motor speed to increase by 40RPM based on the current speed.

[0080] When the control device receives two consecutive high pressure values ​​of 1.3MPa and 1.2MPa, the control device determines that the high pressure value is decreasing and the latest received high pressure value is in the second pressure range. Therefore, the control device controls the DC motor speed to decrease by 40RPM from the current speed.

[0081] When the control device receives two consecutive high pressure values ​​of 1.0MPa and 0.9MPa, the control device determines that the high pressure value is decreasing and the latest received high pressure value is in the third pressure range. Therefore, the control device controls the DC motor speed to decrease by 20RPM from the current speed.

[0082] When the control device receives two consecutive high pressure values ​​of 0.8MPa and 0.7MPa, the control device determines that the high pressure value is decreasing and the latest received high pressure value exceeds the lower limit of the third pressure range. Therefore, the control device controls the DC motor speed to decrease by 10RPM based on the current speed.

[0083] When the control device determines that the current speed of the DC motor 100 is less than the preset minimum speed, such as 200 RPM, and the latest high pressure value received by the control device is 0.7 MPa, the control device controls the DC motor 110 to stop rotating.

[0084] In one embodiment of the present invention, such as Figure 1 As shown, the DC motor speed control system for a condensing unit based on pressure detection also includes an exhaust temperature sensor 600.

[0085] The detection end of the exhaust temperature sensor 600 is connected to the exhaust pipe, and the output end of the exhaust temperature sensor 600 is connected to the control device.

[0086] The exhaust temperature sensor 600 is used to detect the temperature of the exhaust port of the condenser 100 and send the detected exhaust temperature to the control device.

[0087] The control device is also used to control the DC motor 110 to rotate at the initial speed when the exhaust temperature is not less than the preset temperature and the high pressure value is less than the preset pressure value.

[0088] In one embodiment of the present invention, such as Figure 1 As shown, the DC motor speed control system for condensing units based on pressure detection also includes a display device 700.

[0089] The display device 700 is mounted on the control device;

[0090] The control device is also used to control the display device 700 to display the operating status of the compressor 200 and / or the condenser 100.

[0091] In one embodiment of the present invention, such as Figure 1 As shown, the DC motor speed control system for a condensing unit based on pressure detection also includes an electric heating belt 800 and a liquid injection solenoid valve 900.

[0092] The electric heating belt 800 is disposed at the bottom of the compressor 200; the control end of the electric heating belt 800 is connected to the control device;

[0093] The liquid injection solenoid valve 900 is installed in the refrigerant pipeline connected to the compressor 200, and the control terminal of the liquid injection solenoid valve 900 is connected to the control device.

[0094] The control device is also used to control the working state of the electric heating belt 800;

[0095] The control device is also used to control the working state of the liquid spraying solenoid valve 900;

[0096] Specifically, one end of the electric heating strip 800 is connected to the output end of the control device, and the other end of the electric heating strip 800 is connected to the common neutral wire terminal 560 on the control device. One end of the liquid spraying solenoid valve 900 is connected to the output end of the control device, and the other end of the liquid spraying solenoid valve 900 is connected to the common neutral wire terminal 560 on the control device.

[0097] In one embodiment of the present invention, such as Figure 1As shown, the DC motor speed control system for a condensing unit based on pressure detection also includes a bypass solenoid valve 1000.

[0098] One end of the bypass solenoid valve 1000 is connected to the intake pipe of the compressor 200, and the other end of the bypass solenoid valve 1000 is connected to the exhaust pipe of the compressor 200.

[0099] The control device is also used to control the bypass solenoid valve 1000 to open before starting the compressor 200;

[0100] The control device is also used to control the bypass solenoid valve 1000 to close after the bypass solenoid valve 1000 has been open for a period of not less than a preset time, and to control the compressor 200 to start.

[0101] In one embodiment of the present invention, the DC motor speed control system for a condensing unit based on pressure detection further includes a first pressure sensor and a second pressure sensor.

[0102] The first pressure sensor is disposed in the intake pipe of the compressor 200, and the second pressure sensor is disposed in the exhaust pipe of the compressor 200.

[0103] The output terminals of the first pressure sensor and the second pressure sensor are respectively connected to the input terminal of the control device;

[0104] The first pressure sensor is used to detect the intake pressure at the intake port of the compressor 200 and send it to the control device;

[0105] The second pressure sensor is used to detect the exhaust pressure at the exhaust port of the compressor 200 and send it to the control device;

[0106] The control device is also used to control the bypass solenoid valve 1000 to open when the received difference between the exhaust pressure and the return pressure is greater than the preset pressure before the compressor 200 is started.

[0107] After the bypass solenoid valve 1000 is opened, when the intake pressure and exhaust pressure received by the control device are balanced, the control device is also used to control the bypass solenoid valve 1000 to close and control the compressor 200 to start.

[0108] Obviously, the above embodiments are merely examples to more clearly illustrate the technical solution of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description, and these variations, without departing from the concept of the present invention, all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A DC motor speed control system for a condensing unit based on pressure detection, characterized in that, Including condenser (100), compressor (200), high-pressure sensor (300), ambient temperature sensor (400) and control device; wherein, the condenser (100) is provided with an exhaust pipe and at least one DC motor (110); The control device includes a switching power supply module (540) and at least one motor drive board (550); The DC motor (110) is connected to the output terminal of the motor drive board (550), and the power supply terminal of the motor drive board (550) is connected to the switching power supply module (540). The high-pressure sensor (300) is installed at the high-pressure pipe of the condenser (100), and the output end of the high-pressure sensor (300) is connected to the input end of the control device; the ambient temperature sensor (400) is installed outside the condenser (100), and the output end of the ambient temperature sensor (400) is connected to the input end of the control device. The high-pressure sensor (300) is used to detect the pressure in the high-pressure pipeline of the condenser (100) according to a preset cycle, and send the detected high-pressure value to the control device; The ambient temperature sensor (400) is used to detect the temperature of the environment in which the condenser (100) is located, and to send the detected ambient temperature to the control device; The control device is used to generate the initial speed of the DC motor (110) based on the ambient temperature; When the high pressure value is not less than the preset pressure value, the control device is used to control the DC motor (110) to rotate at the initial speed; The control device is also used to control the speed of the DC motor (110) based on the changing trend of two consecutive received high pressure values ​​and the high pressure value. The control device also includes an AC contactor (510), a compressor terminal (520), and a power input terminal (530); The compressor (200) is connected to one end of the AC contactor (510) through the compressor terminal (520), and the other end of the AC contactor (510) is connected to the power input terminal (530); It also includes a bypass solenoid valve (1000); One end of the bypass solenoid valve (1000) is connected to the intake pipe of the compressor (200), and the other end of the bypass solenoid valve (1000) is connected to the exhaust pipe of the compressor (200). The control device is further configured to control the bypass solenoid valve (1000) to open before starting the compressor (200); the control device is further configured to control the bypass solenoid valve (1000) to open after the bypass solenoid valve (1000) has been open for a period not less than a preset time. The bypass solenoid valve (1000) is closed, and the compressor (200) is started. It also includes a first pressure sensor and a second pressure sensor; The first pressure sensor is disposed in the intake pipe of the compressor (200), and the second pressure sensor is disposed in the exhaust pipe of the compressor (200). The output terminals of the first pressure sensor and the second pressure sensor are respectively connected to the input terminal of the control device; The first pressure sensor is used to detect the intake pressure of the compressor (200) intake port and send it to the control device; The second pressure sensor is used to detect the exhaust pressure at the exhaust port of the compressor (200) and send it to the control device; The control device is also used to control the bypass solenoid valve (1000) to open when the received exhaust pressure is greater than the preset start pressure before the compressor (200) starts. After the bypass solenoid valve (1000) is opened, when the intake pressure and exhaust pressure received by the control device are balanced, the control device is also used to control the bypass solenoid valve (1000) to close and control the compressor (200) to start.

2. The DC motor speed control system for a condensing unit based on pressure detection as described in claim 1, characterized in that, When two consecutive high-pressure values ​​received by the control device show an upward trend, and the latest received high-pressure value is within the first pressure range, the control device is also used to control the speed of the DC motor (110) to increase by a first preset speed value. When two consecutive high pressure values ​​received by the control device show an upward trend, and the latest high pressure value exceeds the upper limit of the first pressure range, the control device is also used to control the speed of the DC motor (110) to increase by a second preset speed value. When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest received high pressure value is in the second pressure range, the control device is also used to control the speed of the DC motor (110) to decrease by a second preset speed value. When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest high pressure value is in the third pressure range, the control device is also used to control the speed of the DC motor (110) to decrease by a first preset speed value. When the control device receives two consecutive high pressure values ​​that show a downward trend, and the latest high pressure value exceeds the lower limit of the third pressure range, the control device is also used to control the speed of the DC motor (110) to decrease by a third preset speed value. When the current speed of the DC motor (110) is less than the preset minimum speed, and the high pressure value received by the control device exceeds the lower limit of the third pressure range, the control device is also used to control the DC motor (110) to stop rotating.

3. The DC motor speed control system for a condensing unit based on pressure detection as described in claim 2, characterized in that, Let the preset pressure value be a, the first pressure range be [c, e), the second pressure range be (d, f], and the third pressure range be (b, d]. The preset pressure value 'a' ranges from 0.8 to 1.0 MPa, the lower limit 'c' of the first pressure ranges from 1.0 to 1.2 MPa, the upper limit 'e' of the first pressure ranges from 1.2 to 1.4 MPa, the lower limit 'd' of the second pressure ranges from 0.9 to 1.2 MPa, the upper limit 'f' of the second pressure ranges from 1.1 to 1.3 MPa, and the lower limit 'b' of the third pressure ranges from 0.7 to 0.9 MPa.

4. The DC motor speed control system for condensing units based on pressure detection as described in claim 2, characterized in that, The first preset speed value is 20-50 RPM, the second preset speed value is 30-80 RPM, and the third preset speed value is 10-30 RPM.

5. The DC motor speed control system for a condensing unit based on pressure detection as described in claim 1, characterized in that, Let the initial speed of the DC motor (110) be S0, and the ambient temperature be T; The initial speed S0 of the DC motor (110) generated by the control device based on the ambient temperature is specifically: S0 = min(T / 30*800, 800) RPM.

6. The DC motor speed control system for a condensing unit based on pressure detection as described in claim 1, characterized in that, It also includes an exhaust temperature sensor (600); The detection end of the exhaust temperature sensor (600) is connected to the exhaust pipe, and the output end of the exhaust temperature sensor (600) is connected to the control device. The exhaust temperature sensor (600) is used to detect the temperature of the exhaust port of the condenser (100) and send the detected exhaust temperature to the control device; The control device is also used to control the DC motor (110) to rotate at the initial speed when the exhaust temperature is not less than the preset temperature and the high pressure value is less than the preset pressure value.

7. The DC motor speed control system for a condensing unit based on pressure detection as described in claim 1, characterized in that, It also includes a display device (700); The display device (700) is mounted on the control device; The control device is also used to control the display device (700) to display the operating status of the compressor (200) and / or the condenser (100).

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