Vacuum screw pump set control method

Abstract

The invention provides a vacuum screw pump set control method. The method comprises the steps that a target value of the needed vacuum degree is input; obtaining an actual value of the vacuum degree of the equipment; obtaining a comparison result of the target value and the actual value; and according to the comparison result, the control system regulates and controls the operation frequency of the screw pump and the operation frequency of the roots pump. Compared with a single-frequency-conversion control method in the prior art, a double-frequency-conversion control method is adopted in the control method, the operation frequency of the screw pump and the operation frequency of the roots pump are controlled at the same time, so that the pumping speed range of the vacuum screw pump set is greatly expanded, and the pumping speed of the vacuum screw pump set is greatly increased through the control method under the condition that a pump body is not replaced. And the pumping speed adjusting range of an original pump set is expanded, so that the pump set can meet more pumping speed adjusting requirements, and an existing upgraded crystal pulling production process is further matched. And according to the comparison result of the actual value and the target value, a corresponding adjustment program is made, so that the vacuum degree in the equipment cavity can meet the requirement, and errors are reduced.

Description

Technical Field

[0001] This application relates to the technical field of vacuum screw pump sets, and particularly to a control method for a vacuum screw pump set. Background Art

[0002] In the photovoltaic crystal pulling industry, a vacuum screw pump set is required to evacuate to accurately control the vacuum degree, thereby ensuring the stability of the crystal growth process.

[0003] However, the existing vacuum screw pump set adopts a single frequency conversion control method. In this method, the host computer only controls the operating frequency of the Roots pump in real time and does not control the operating frequency of the screw pump, resulting in a small pumping speed adjustment range of the vacuum screw pump set, which can no longer meet the pumping speed requirements of the existing crystal pulling production process for the vacuum screw pump set.

[0004] Therefore, there is room for further improvement in the control method of the existing vacuum screw pump set. Summary of the Invention

[0005] In view of this, in response to the technical problem of the small pumping speed adjustment range caused by the single frequency conversion control in the existing vacuum screw pump set, this application provides a control method for a vacuum screw pump set, which adopts a double frequency conversion control method, can increase the pumping speed adjustment range, and has a wider application range.

[0006] This application provides a control method for a vacuum screw pump set, including:

[0007] Input the target value of the required vacuum degree;

[0008] Obtain the actual value of the equipment vacuum degree;

[0009] Obtain the comparison result between the target value and the actual value;

[0010] According to the comparison result, the control system respectively regulates the operating frequencies of the screw pump and the Roots pump.

[0011] Compared with the prior art, in the control method of the vacuum screw pump unit of the present application, when the detected actual vacuum degree does not reach the set value, the control system calculates and controls the operating frequencies of the screw pump and the roots pump respectively, so that the operating frequencies of the roots pump and the screw pump operate according to the set values. As a result, after the pump unit outputs and operates, the vacuum degree of the equipment can reach the set target value. Compared with the single-frequency conversion control method of the prior art, the double-frequency conversion control method is adopted in the control method of the present application to control the operating frequencies of the screw pump and the roots pump at the same time, thus greatly expanding the pumping speed range of the vacuum screw pump unit. Without replacing the pump body, through this control method, the pumping speed adjustment range of the original pump unit is expanded, so that the pump unit can meet more pumping speed adjustment requirements and further match the existing upgraded crystal pulling production process. And according to the comparison result between the actual value and the target value, a corresponding adjustment program is made, so that the vacuum degree in the equipment cavity can meet the requirements and the error is reduced.

[0012] Preferably, the comparison result includes that the actual value is equal to or not equal to the target value;

[0013] When the actual value is equal to the target value, the control system controls the drive system to execute according to the direct operation program;

[0014] When the actual value is not equal to the target value, the control system controls the drive system to execute according to the difference adjustment program.

[0015] Preferably, the difference adjustment program includes:

[0016] The control system obtains the difference adjustment variables of the operating frequencies of the roots pump and the screw pump according to the current pumping speeds of the roots pump and the screw pump;

[0017] According to the difference adjustment variables, the control system adjusts based on the current operating frequencies of the roots pump and the screw pump;

[0018] The drive system drives the roots pump and the screw pump to operate according to the adjusted operating frequencies respectively based on the adjusted operating frequencies.

[0019] Preferably, the operating frequency includes the operating frequency of the drive part and the operating frequency of the execution part of the roots pump or the screw pump;

[0020] Among them, the operating frequency of the drive part is the operating frequency of the frequency converter, and the operating frequency of the execution part is the motor speed.

[0021] Preferably, it further includes a balance self-check program, and the balance self-check program includes:

[0022] The control system respectively obtains n operating frequency values of the roots pump and the screw pump within T1 time, and judges whether the roots pump and the screw pump operate in balance.

[0023] Preferably, when both the roots pump and the screw pump are operating in balance, the control system controls the drive system to execute according to the direct operation program;

[0024] When either the roots pump or the screw pump is operating unbalanced, the control system controls the drive system to execute according to the balance adjustment program.

[0025] Preferably, the balance adjustment program includes:

[0026] The drive system controls the motor of the unbalanced pump to increase or decrease the frequency until it is directly balanced.

[0027] Preferably, after the vacuum screw pump unit operates, the control system automatically starts the balance self-check program at an interval of T2.

[0028] Preferably, when inputting the target value of the required vacuum degree, it further includes: the control system determines whether the target value is within the specified range;

[0029] When the target value is within the specified range, the control system executes the next program;

[0030] When the target value is not within the specified range, the control system prompts the user to re-enter the target value.

[0031] Preferably, when obtaining the actual value of the equipment vacuum degree, it further includes: the control system controls the detection system to detect the current vacuum degree of the equipment, and the detection system transmits the detected data to the control system;

[0032] Among them, after the vacuum screw pump unit operates, the detection system transmits the detected actual value to the control system at an interval of T3. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic flowchart of a control method for a vacuum screw pump unit provided by an embodiment of the present application;

[0034] Figure 2 is a control block diagram of a control method for a vacuum screw pump unit provided by an embodiment of the present application;

[0035] Figure 3 is a test comparison diagram provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to enable those skilled in the art to better understand the technical solutions of the present disclosure, the following will describe the present disclosure in detail, clearly and completely with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present disclosure and are not used to limit the present disclosure.

[0037] In the description of the present application, if the first and the second are described only for the purpose of distinguishing technical features, they should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features or the sequence of the indicated technical features.

[0038] Those skilled in the art should understand that in the disclosure of the present application, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present application.

[0039] The following further describes the present application in detail with reference to the drawings, as shown in Figures 1 to 3 description.

[0040] The present application provides a control method for a vacuum screw pump set, which is used to control the operating frequencies of the screw pump and the roots pump of the vacuum screw pump set, so as to control the pumping speed of the vacuum screw pump set (hereinafter referred to as the pump set). Without replacing the pump body, through this dual-frequency control method, the pumping speed adjustment range of the original pump set can be broadened, so that the pump set can meet more pumping speed adjustment requirements, further match the existing upgraded crystal pulling production process, and save costs.

[0041] Specifically, the control method for the vacuum screw pump set of the present application specifically includes:

[0042] Step S1: Input the target value of the required vacuum degree;

[0043] Step S2: Obtain the actual value of the equipment vacuum degree;

[0044] Step S3: Obtain the comparison result between the target value and the actual value;

[0045] Step S4: According to the comparison result, the control system respectively regulates the operating frequencies of the screw pump and the roots pump.

[0046] In this embodiment, as Figure 1 , Figure 2As shown in the figure, in step S1, the user inputs the target value of the required vacuum degree through the host computer; after the pump group runs, the control system starts the differential self-checking program. This differential self-checking program is that the control system obtains the actual value of the equipment vacuum degree, then compares the target value with the actual value to obtain the comparison result; the control system then controls the running frequencies of the screw pump and the Roots pump respectively according to the comparison result, that is, performs double-frequency control on the pump group. By simultaneously controlling the running frequencies of the screw pump and the Roots pump, the speed regulation range of the pump group is widened, and then the adjustment range of the vacuum pump is widened to meet the existing upgraded crystal pulling production process.

[0047] It should be noted that in this embodiment, the running frequency includes the running frequency of the running part and the executing part of the Roots pump, as well as the running frequency of the running part and the executing part of the screw pump; the drive system is used to control the running parts and the executing parts of the two pumps. Among them, the running frequency of the driving part is the running frequency of the frequency converter, and the running frequency of the executing part is the motor speed.

[0048] In this application, the control method of the existing vacuum screw pump group is a single-frequency control method, that is, only the running frequency of the Roots pump is controlled to change, and the running frequency of the screw pump remains unchanged. Compared with this existing single-frequency control method, the principle of the double-frequency control method of this application to change the pumping speed adjustment range of the pump group is as follows:

[0049] Total pumping speed formula:

[0050] The total pumping speed S_total of the series pump group is jointly determined by the pumping speeds S_1 (screw pump) and S_2 (Roots pump) of the two pumps:

[0051]

[0052] Pumping speed range of the existing technology single-frequency control system (constant frequency of screw pump, variable frequency of Roots pump):

[0053] When the screw pump is at a constant frequency (S_1 = S_1_0, fixed) and the Roots pump is at a variable frequency (S_2 ∈ [S_2_min, S_2_max]), the total pumping speed range is:

[0054]

[0055] Pumping speed range of the double-frequency control system of this application (variable frequency of screw pump, variable frequency of Roots pump):

[0056] When the screw pump is at a variable frequency (S_1 ∈ [S_1_min, S_1_max]) and the Roots pump is at a variable frequency (S_2 ∈ [S_2_min, S_2_max]), the total pumping speed range is:

[0057]

[0058] As can be seen from the above, since S_1_min < S_1_0, the lower limit of the pumping speed in the dual-frequency control method of the present application is smaller:

[0059]

[0060] Since S_1_max > S_1_0, the upper limit of the pumping speed in the dual-frequency control method of the present application is larger:

[0061]

[0062] Therefore, in the control method of the vacuum screw pump unit of the present application, by allowing both the screw pump and the roots pump to operate with variable frequency, the minimum value of the total pumping speed is reduced and the maximum value is increased, thereby expanding the pumping speed range of the system. The above formula shows that the dual-pump variable frequency breaks through the limitations of the single-pump variable frequency by coordinately adjusting S_1 and S_2, and realizes a wider pumping speed adjustment ability.

[0063] Further, in step S1, it specifically includes: the control system determines whether the target value is within the specified range, and the system has preset the selection range of the required vacuum degree;

[0064] When the target value input by the user is within the specified range, the control system executes the next program, that is, the control system controls the screw pump and the roots pump to operate according to the set direct operation program respectively;

[0065] When the target value input by the user is not within the specified range, the control system issues a prompt, issues a re-input prompt on the display screen or the control panel to prompt the user to re-enter the target. At this time, the screw pump and the roots pump will not operate until the control system detects again that the input target value is within the specified range, and the control system will drive the pump unit to operate.

[0066] Further, as Figure 1 shown, after step S1, step S2 specifically includes: the control system controls the detection system to detect the current vacuum degree of the equipment, the detection system transmits the detected data to the control system, and the control system records the actual value of the transmitted vacuum degree; among them, when step S1 ends, the control system controls the vacuum screw pump unit to operate. After the vacuum screw pump unit operates for a period of time, the detection system automatically detects at intervals of T3 time and transmits the detected actual value to the control system.

[0067] In the embodiment, the detection system includes a vacuum degree detection sensor, which is arranged in the cavity of the crystal pulling tank body to detect the vacuum degree in the equipment cavity. Among them, T3 is approximately about 100 ms. In actual use, the size of T3 can be selected according to actual needs.

[0068] Further, as Figure 1As shown, after step S2, step S3 specifically includes: after the control system compares the actual value with the target value, the comparison result includes two results: the actual value is equal to or not equal to the target value;

[0069] When the actual value of the equipment vacuum degree obtained by the control system is equal to the target value, the control system controls the drive system to execute according to the direct operation program, that is, the vacuum pump and the screw pump respectively operate directly at the operation frequency corresponding to the target value.

[0070] When the actual value of the equipment vacuum degree obtained by the control system is not equal to the target value, the control system controls the drive system to execute according to the difference adjustment program, that is Figure 2 the control loop 1 in; that is, on the basis of the original operation frequency corresponding to the target value, the control system makes a difference adjustment to the operation frequency, including increasing or decreasing the operation frequency, so that the actual value of the equipment vacuum degree can finally be equal to the target value and meet the user's vacuum degree requirement.

[0071] In this embodiment, the setting of the difference adjustment program makes the output accuracy of the vacuum screw pump group higher, ensures that after the pump group outputs, the vacuum degree in the equipment cavity can be the same as the target value, reduces errors, accurately meets the user's vacuum degree requirement, and can better meet the production requirement of the crystal pulling process.

[0072] Specifically, the difference adjustment program includes:

[0073] Based on the current pumping speed of the roots pump and the screw pump, the control system respectively obtains the difference adjustment variables of the operation frequencies of the screw pump and the roots pump through a series of calculations, and the difference adjustment variables include the operation frequency of the drive part and the operation frequency of the execution part;

[0074] According to the difference adjustment variables, the control system makes adjustments based on the current operation frequencies of the roots pump and the screw pump, that is, adjusts the operation frequencies of the drive part and / or the execution part of the roots pump and the screw pump to obtain the adjusted operation frequencies;

[0075] The drive system drives the screw pump and the roots pump to operate at the adjusted operation frequencies respectively based on the adjusted operation frequencies, so that the vacuum degrees after the screw pump and the roots pump operate can meet the target value requirements.

[0076] It should be noted that in this application, as Figure 1 shown, after each adjustment of the difference adjustment program, after the vacuum screw pump group operates for a period of time, the detection system detects again and then compares the actual value with the target value again to repeat the difference adjustment program in steps S3 and S4 above until the detected target value and actual value are equal.

[0077] On the basis of any of the above embodiments, further expansion is made; as Figure 1As shown, the control method of the vacuum screw pump set of the present application further includes a balance self-check program; the balance self-check program includes:

[0078] The control system respectively obtains n operating frequency values of the roots pump and the screw pump within T1 time, that is, within the duration of T1, the detection system detects the operating frequencies of the execution part and the drive part of the roots pump and the screw pump, and extracts n operating frequency values among them. The operating frequency value can be the operating frequency value of a single execution part or drive part of the roots pump or the screw pump, or the total output operating frequency value of the entire roots pump or the screw pump. By comparing, analyzing, and judging these n operating frequency values, it is determined whether the roots pump and the screw pump are operating in balance.

[0079] It should be noted that the duration of T1 is approximately about 100 ms, and n is a finite value, and its specific data can be selected according to actual needs.

[0080] Specifically, when both the roots pump and the screw pump are operating in balance, the control system controls the drive system to execute according to the direct operation program, that is, the drive system continues to drive the roots pump and the screw pump according to the operation program when the above actual value is equal to the target value.

[0081] When any one of the roots pump and the screw pump is operating unbalanced, the control system controls the drive system to execute according to the balance adjustment program, that is Figure 2 the control loop 2 in; specifically, as Figure 1 shown, the balance adjustment program includes:

[0082] The control system outputs a balance adjustment variable to the drive system. According to this balance adjustment variable, the drive system controls the drive part of the unbalanced pump body (screw pump or roots pump) to increase or decrease the frequency of the motor until it is directly balanced.

[0083] It should be noted that after the vacuum screw pump set runs, the control system automatically starts the balance self-check program at intervals of T2 time. If it is unbalanced, the above balance adjustment program will be automatically run. T2 is approximately 500 ms. After the vacuum screw pump set adopts the balance self-check program and the balance adjustment program, the running stability of the vacuum screw pump set is increased, making the required vacuum degree in the crystal pulling tank more stable.

[0084] Such as Figure 1 shown, in the present application, the balance self-check program and the difference self-check program will be automatically started at intervals of the corresponding duration during the operation of the vacuum screw pump set; when the balance self-check program triggers the balance adjustment program, and the difference self-check program triggers the difference adjustment program, they will be executed according to the corresponding programs, so as to ensure the stability and accuracy of the vacuum screw pump set during operation.

[0085] It should be noted that in the present application, the screw pump in the vacuum screw pump set adopts a permanent magnet synchronous motor.

[0086] In addition, as Figure 3 shown, the experimental test diagrams of the vacuum screw pump unit before and after adopting the control method of the present application are provided. Among them, Figure 3 (a) in is the test diagram of the existing vacuum screw pump unit before adopting the control method of the present application, Figure 3 (b) in is the test diagram of the existing vacuum screw pump unit after adopting the control method of the present application; according to Figure 3 the test diagrams, the following comparison table 1 can be obtained:

[0087] Average frequency of screw pump Average frequency of roots pump Average power of roots pump kW Before use 224 16 2.2 After use 242 15 1.7

[0088] Table 1

[0089] According to the following formula:

[0090] Frequency = K1 * Rotational speed = K2 * Pumping speed;

[0091] It can be known that after the vacuum screw pump unit adopts the control method of the present application, while broadening the pumping speed range of the pump unit, the average frequency and power of its roots pump are significantly reduced, reducing the power consumption of the roots pump, so that the roots pump will not overheat after use, avoiding the occurrence of the situation of pump shutdown due to high temperature, protecting the roots pump, and increasing the service life of the roots pump.

[0092] It should be noted that in the case where the embodiments of the present application do not conflict with each other and the technical solutions can coexist, they can be arbitrarily combined into new embodiments.

[0093] The present application has been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the present application and its core idea. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present application, several improvements and modifications can still be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A control method for a vacuum screw pump unit, characterized in that, Including: Input the target value of the required vacuum degree; Obtain the actual value of the equipment vacuum degree; Obtain the comparison result between the target value and the actual value; According to the comparison result, the control system adjusts the operating frequencies of the screw pump and the roots pump respectively.

2. The control method for a vacuum screw pump unit according to claim 1, characterized in that The comparison result includes that the actual value is equal to or not equal to the target value; When the actual value is equal to the target value, the control system controls the drive system to execute according to the direct operation program; When the actual value is not equal to the target value, the control system controls the drive system to execute according to the difference adjustment program.

3. The control method for a vacuum screw pump unit according to claim 2, characterized in that The difference adjustment program includes: The control system obtains the difference adjustment variables of the operating frequencies of the screw pump and the roots pump according to the current pumping speed of the roots pump and the screw pump; According to the difference adjustment variables, the control system adjusts based on the current operating frequencies of the roots pump and the screw pump; The drive system drives the screw pump and the roots pump to operate according to the adjusted operating frequencies respectively based on the adjusted operating frequencies.

4. The control method for a vacuum screw pump unit according to claim 1, characterized in that The operating frequency includes the operating frequency of the drive part and the operating frequency of the execution part of the roots pump or the screw pump; Among them, the operating frequency of the drive part is the operating frequency of the frequency converter, and the operating frequency of the execution part is the motor speed.

5. The control method for a vacuum screw pump unit according to claim 1, characterized in that It also includes a balance self-check program, and the balance self-check program includes: The control system respectively obtains n operating frequency values of the roots pump and the screw pump within T1 time, and judges whether the roots pump and the screw pump are operating in balance.

6. The control method for a vacuum screw pump unit according to claim 5, characterized in that When both the roots pump and the screw pump are operating in balance, the control system controls the drive system to execute according to the direct operation program; When any one of the roots pump and the screw pump is operating unbalanced, the control system controls the drive system to execute according to the balance adjustment program.

7. The control method for a vacuum screw pump unit according to claim 6, characterized in that The balance adjustment program includes: The drive system controls the motor of the unbalanced pump to increase or decrease the frequency until it is directly balanced.

8. The control method for a vacuum screw pump unit according to any one of claims 5 to 7, characterized in that After the vacuum screw pump unit operates, the control system automatically starts the balance self-check program at an interval of T2 time.

9. The control method for a vacuum screw pump unit according to claim 1, characterized in that When inputting the target value of the required vacuum degree, it also includes: the control system judges whether the target value is within the specified range; When the target value is within the specified range, the control system executes the next program; When the target value is not within the specified range, the control system prompts the user to re-enter the target value.

10. The control method for a vacuum screw pump unit according to claim 1, characterized in that In obtaining the actual value of the equipment vacuum degree, it also includes: the control system controls the detection system to detect the current vacuum degree of the equipment, and the detection system transmits the detected data to the control system; Among them, after the vacuum screw pump unit operates, the detection system transmits the actually detected value to the control system at an interval of T3 time.

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