Pipe vacuum closed-loop frequency conversion control system
By employing a closed-loop frequency conversion control system with dual comparators and dual relays in pipe production, the problem of inaccurate vacuum control was solved, achieving high-precision and low-cost vacuum control, and improving production stability and product quality.
Patent Information
- Application Number
- CN202410537563.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-30
- Publication Date
- 2025-10-31
AI Technical Summary
In the current pipe production process, the vacuum control accuracy is inaccurate and easily affected by voltage fluctuations and external interference, resulting in high production costs and unstable product quality.
By adding two comparators and two relays, the analog input is converted into a three-bit digital output. Combined with a voltage divider circuit and relay design, closed-loop control of the vacuum level is achieved, improving control accuracy. Furthermore, cost is reduced through relay protection and alarm optimization.
The system improves the accuracy of vacuum control under voltage fluctuations and external interference, reduces system costs, solves the problem of frequent alarm operation, and improves system reliability and production stability.
Smart Images
Figure CN120862933A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of vacuum shaping tables for pipes, and in particular to a closed-loop frequency conversion control system for vacuum pipes. Background Technology
[0002] During pipe production, the product needs to be cooled and shaped. In the early stages, pressure relief valves were used to manually control the vacuum level, which required frequent manual operation and often resulted in significant power waste during normal production. If the vacuum was too low, the pipe blank would not be easy to form; if the vacuum was too high, the pipe diameter would be too large, making it difficult to guarantee qualified products, resulting in wasted raw materials and high production costs.
[0003] In response, those skilled in the art use closed-loop automatic control to control the vacuum level. Generally, existing technologies include a pressure transmitter, a pressure controller, and a frequency converter. After the pressure transmitter collects the air pressure, it inputs it to the pressure controller. The pressure controller determines whether the pressure collected by the pressure transmitter exceeds a pre-configured threshold and then decides whether to start the vacuum pump. In a frequency converter system, the pressure transmitter typically outputs a voltage signal to the pressure controller. The higher the pressure (the lower the vacuum level), the higher the voltage. The frequency converter adjusts the PWM duty cycle based on the magnitude of this voltage, thereby controlling the speed of the vacuum pump motor.
[0004] However, in the existing technology, since a linear control method is formed by relying on the magnitude of the voltage, if the voltage value deviates, the speed control is easily inaccurate, and the control accuracy is poor when the power supply is unstable or there are too many interfering devices. Summary of the Invention
[0005] The purpose of this invention is to provide a vacuum closed-loop frequency conversion control system for pipes. By adding two comparators and two relays, the analog input is converted into a three-bit digital output, thereby improving control accuracy under voltage fluctuations and external interference. Compared with traditional analog-to-digital conversion methods, it has the advantages of low cost and high reliability.
[0006] The objective of this invention can be achieved through the following technical solutions:
[0007] A vacuum closed-loop variable frequency control system for pipes includes a vacuum pump, a contactor, a frequency converter, a pressure transmitter, and a pressure controller. The power input terminal of the frequency converter is connected to a three-phase power supply, and the power output terminal is connected to the vacuum pump through the contacts of the contactor. The pressure controller is connected to both the pressure transmitter and the frequency converter. The pressure controller includes a voltage divider circuit, a first comparator circuit, a second comparator circuit, a first relay, a second relay, and a third relay. One end of the voltage divider circuit is connected to the output terminal of the pressure transmitter, and the other end is grounded.
[0008] The non-inverting input of the first comparator circuit is connected to the voltage divider output of the voltage divider circuit, the inverting input is connected to the first reference power supply, the output is connected to the coil of the second relay, and the normally open terminal of the second relay is connected to the first control signal input of the frequency converter.
[0009] The non-inverting input of the second comparator circuit is connected to the voltage divider output of the voltage divider circuit, the inverting input is connected to the second reference power supply, and the output is connected to the coil of the third relay. The normally open terminal of the third relay is connected to the second control signal input of the frequency converter. The voltage of the second reference power supply is different from that of the first reference power supply.
[0010] The coil of the first relay is connected to the voltage divider output terminal of the voltage divider circuit, and the normally open terminal is connected to the first enable signal input terminal of the frequency converter.
[0011] The control system also includes a protection relay. The first relay is a double-pole double-throw relay. The normally open terminal of the first set of contacts of the first relay is connected to the first enable signal input terminal of the frequency converter, and the normally open terminal of the second set of contacts is connected to the coil of the protection relay. The normally open terminal of the protection relay is connected to the coil of the contactor.
[0012] The control system also includes a first manual switch, which is connected in parallel with the normally open terminal of the protection relay.
[0013] The common terminal of the first set of contacts of the first relay is connected to the 24V DC output terminal of the frequency converter.
[0014] The contactor's coil is connected in series with a thermal protector.
[0015] A circuit breaker is provided between the frequency converter and the three-phase power supply.
[0016] The control system also includes an alarm, and both the second and third relays are double-pole double-throw relays.
[0017] The normally open terminal of the first set of contacts of the second relay is connected to the first control signal input terminal of the frequency converter.
[0018] The normally open terminal of the first set of contacts of the third relay is connected to the second control signal input terminal of the frequency converter.
[0019] The normally open terminals of the second set of contacts of the second and third relays are both connected to the alarm.
[0020] A second manual switch is provided between the alarm and the second and third relays.
[0021] The alarm is an audible and visual alarm.
[0022] The common terminal of the second and third relays is connected to a low-voltage DC power supply.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] 1. By adding two comparators and two relays, the analog input is converted into a three-bit digital output, which can improve the control accuracy under voltage fluctuations and external interference. Compared with the traditional analog-to-digital conversion method, it has the advantages of low cost and high reliability.
[0025] 2. The output of the first relay also serves as an enable signal, which can reduce the occupation of the inverter input pins, thus preserving a certain degree of expandability.
[0026] 3. By setting a protective relay as the transition of the enable signal, the pressure transmitter can be effectively protected.
[0027] 4. The contactor coil is connected in series with a thermal protector to achieve thermal protection.
[0028] 5. By designing the second and third relays to be double-pole double-throw relays, and connecting their second set of contacts in parallel as the signal to drive the alarm, the problem of frequent alarm operation can be solved. Attached Figure Description
[0029] Figure 1 This is a schematic diagram of the structure of the present invention;
[0030] Figure 2 This is a circuit diagram of the secondary side of the pressure controller of the present invention;
[0031] Figure 3 This is a circuit diagram of the contactor section;
[0032] Figure 4 This is a circuit diagram of the alarm section;
[0033] Figure 5 This is a schematic diagram of the primary side of the present invention;
[0034] The components are: 1. Vacuum pump, 2. Frequency converter, 3. Pressure controller, 4. Pressure transmitter, K1. First relay, K2. Second relay, K3. Third relay, K4. Protection relay, R1. First resistor, R2. Second resistor, R3. Third resistor, R4. Fourth resistor, R5. Fifth resistor, R6. Sixth resistor, R7. Seventh resistor, U1. First comparator circuit, U2. Second comparator circuit, KM. Contactor, Vin. Pressure transmission output voltage, VCC. Reference voltage, Vref1. First voltage power supply, Vref2. Second reference power supply, S1. First manual switch, FR1. Thermal protector, VDD2. Low-voltage DC power supply, P1. Alarm, QF1. Circuit breaker. Detailed Implementation
[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.
[0036] A vacuum closed-loop frequency conversion control system for pipes, such as Figures 1 to 5 As shown, the system includes a vacuum pump 1, a contactor KM, a frequency converter 2, a pressure transmitter 4, and a pressure controller 3. The power input terminal of the frequency converter 2 is connected to a three-phase power supply, and its power output terminal is connected to the vacuum pump 1 through the contacts of the contactor KM. The pressure controller 3 is connected to both the pressure transmitter 4 and the frequency converter 2. The pressure controller 3 includes a voltage divider circuit, a first comparator circuit U1, a second comparator circuit U2, a first relay K1, a second relay K2, and a third relay K3. One end of the voltage divider circuit is connected to the output terminal of the pressure transmitter 4, and the other end is grounded.
[0037] The non-inverting input of the first comparator circuit U1 is connected to the voltage divider output of the voltage divider circuit, the inverting input is connected to the first reference power supply Vref1, the output is connected to the coil of the second relay K2, and the normally open terminal of the second relay K2 is connected to the first control signal input of the frequency converter 2.
[0038] The non-inverting input of the second comparator circuit U2 is connected to the voltage divider output of the voltage divider circuit, the inverting input is connected to the second reference power supply Vref2, and the output is connected to the coil of the third relay K3. The normally open terminal of the third relay K3 is connected to the second control signal input of the frequency converter 2. The voltage of the second reference power supply Vref2 is different from that of the first reference power supply Vref1.
[0039] The coil of the first relay K1 is connected to the voltage divider output terminal of the voltage divider circuit, and its normally open terminal is connected to the first enable signal input terminal of the frequency converter 2.
[0040] By adding two comparators and two relays, the analog input is converted into a three-bit digital output, thereby improving control accuracy under voltage fluctuations and external interference. Compared with traditional analog-to-digital conversion methods, it has the advantages of low cost and high reliability.
[0041] Furthermore, the output of the first relay K1 also serves as an enable signal, which can indicate the occupation of the input pin of the frequency converter 2, thus retaining a certain degree of expandability.
[0042] In most embodiments, the control system also includes a protection relay K4. The first relay K1 is a double-pole double-throw relay with a first set of contacts K1A and a second set of contacts KAB (not shown). The normally open terminal of the first set of contacts of the first relay K1 is connected to the first enable signal input terminal of the frequency converter 2, and the common terminal is connected to the 24V DC output terminal of the frequency converter 2. The normally open terminal of the second set of contacts is connected to the coil of the protection relay K4, and the normally open terminal of the protection relay K4 is connected to the coil of the contactor KM.
[0043] In addition, in some embodiments, the control system also includes a first manual switch S1, which is connected in parallel with the normally open terminal of the protection relay K4. By setting the protection relay K4 as the transition of the enable signal, the pressure transmitter 4 can be effectively protected.
[0044] When contactor KM is engaged, the inverter's power output is transmitted to the vacuum pump. Through the inputs to the first enable signal input terminal, the first control signal input terminal, and the second control signal input terminal, the inverter generates different duty cycles. The three input terminals sequentially produce a 3-bit digital signal. For example, when all three input terminals are high, meaning the first to third relays are all engaged, the resulting digital signal is 111. At this time, the duty cycle of the inverter's output PWM control signal is at its maximum, and the vacuum pump operates at full speed. Generally, the voltage of the second reference power supply Vref2 is greater than the voltage of the first reference power supply Vref1. As the vacuum level decreases, the output voltage of the pressure transmitter gradually increases. Furthermore, as the vacuum level decreases, the first, second, and third relays are engaged sequentially, thus gradually increasing the duty cycle of the inverter's output PWM control signal. The maximum is 111, followed by 110, and finally 100. By designing the operating current of the first relay and the ratio of the first resistor R1 to the second resistor R2 in the voltage divider circuit, the sensitivity of this control signal can be adjusted.
[0045] Generally, in almost all embodiments, the coil of contactor KM is connected in series with thermal protector FR1, which can achieve thermal protection.
[0046] In most embodiments, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7 are provided to limit current.
[0047] Under normal circumstances, a circuit breaker QF1 or a fuse is installed between the frequency converter 2 and the three-phase power supply.
[0048] Furthermore, in some embodiments, the control system also includes an alarm P1, and the second relay K2 and the third relay K3 are both double-pole double-throw relays. Specifically,
[0049] The normally open terminal of the first set of contacts of the second relay K2 is connected to the first control signal input terminal of the frequency converter 2;
[0050] The normally open terminal of the first set of contacts of the third relay K3 is connected to the second control signal input terminal of the frequency converter 2;
[0051] The normally open terminals of the second set of contacts of the second relay K2 and the third relay K3 are both connected to the alarm P1.
[0052] By designing the second relay K2 and the third relay K3 to be double-pole double-throw relays, and connecting their second set of contacts in parallel as the signal to drive the alarm P1, the problem of frequent operation of the alarm P1 can be solved.
[0053] In some embodiments, a second manual switch is provided between the alarm P1 and the second relay K2 and the third relay K3, or, in some embodiments, the alarm P1 is an audible and visual alarm.
[0054] The common terminal of the second relay K2 and the third relay K3 is connected to a low-voltage DC power supply VDD2, which can be 5V or 12V.
[0055] In this embodiment, the pressure transmitter is JBYG-BA-E2 and the frequency converter is ABB530.
Claims
1. A vacuum closed-loop variable frequency control system for pipes, comprising a vacuum pump, a contactor, a frequency converter, a pressure transmitter, and a pressure controller, wherein the power input terminal of the frequency converter is connected to a three-phase power supply, and the power output terminal is connected to the vacuum pump through the contacts of the contactor; the pressure controller is connected to both the pressure transmitter and the frequency converter, characterized in that... The pressure controller includes a pressure divider circuit, a first comparator circuit, a second comparator circuit, a first relay, a second relay, and a third relay. One end of the pressure divider circuit is connected to the output terminal of the pressure transmitter, and the other end is grounded. The non-inverting input of the first comparator circuit is connected to the voltage divider output of the voltage divider circuit, the inverting input is connected to the first reference power supply, the output is connected to the coil of the second relay, and the normally open terminal of the second relay is connected to the first control signal input of the frequency converter. The non-inverting input of the second comparator circuit is connected to the voltage divider output of the voltage divider circuit, the inverting input is connected to the second reference power supply, and the output is connected to the coil of the third relay. The normally open terminal of the third relay is connected to the second control signal input of the frequency converter. The voltage of the second reference power supply is different from that of the first reference power supply. The coil of the first relay is connected to the voltage divider output terminal of the voltage divider circuit, and the normally open terminal is connected to the first enable signal input terminal of the frequency converter.
2. The vacuum closed-loop frequency conversion control system for pipes according to claim 1, characterized in that, The control system also includes a protection relay. The first relay is a double-pole double-throw relay. The normally open terminal of the first set of contacts of the first relay is connected to the first enable signal input terminal of the frequency converter, and the normally open terminal of the second set of contacts is connected to the coil of the protection relay. The normally open terminal of the protection relay is connected to the coil of the contactor.
3. The vacuum closed-loop frequency conversion control system for pipes according to claim 2, characterized in that, The control system also includes a first manual switch, which is connected in parallel with the normally open terminal of the protection relay.
4. The vacuum closed-loop frequency conversion control system for pipes according to claim 2, characterized in that, The common terminal of the first set of contacts of the first relay is connected to the 24V DC output terminal of the frequency converter.
5. The vacuum closed-loop frequency conversion control system for pipes according to claim 1, characterized in that, The contactor's coil is connected in series with a thermal protector.
6. The vacuum closed-loop frequency conversion control system for pipes according to claim 1, characterized in that, A circuit breaker is provided between the frequency converter and the three-phase power supply.
7. The vacuum closed-loop frequency conversion control system for pipes according to claim 1, characterized in that, The control system also includes an alarm, and both the second and third relays are double-pole double-throw relays. The normally open terminal of the first set of contacts of the second relay is connected to the first control signal input terminal of the frequency converter. The normally open terminal of the first set of contacts of the third relay is connected to the second control signal input terminal of the frequency converter. The normally open terminals of the second set of contacts of the second and third relays are both connected to the alarm.
8. The vacuum closed-loop frequency conversion control system for pipes according to claim 7, characterized in that, A second manual switch is provided between the alarm and the second and third relays.
9. A vacuum closed-loop frequency conversion control system for pipes according to claim 7, characterized in that, The alarm is an audible and visual alarm.
10. A vacuum closed-loop frequency conversion control system for pipes according to claim 1, characterized in that, The common terminal of the second and third relays is connected to a low-voltage DC power supply.