Vacuum equipment variable frequency control system based on PLC

Abstract

The utility model discloses a kind of vacuum pump frequency conversion control system vacuum equipment based on PLC including screw rod pump and Roots pump, the control system includes first frequency converter, second frequency converter, and PLC controller;The screw rod pump is connected with power supply through first frequency converter and first circuit breaker;The Roots pump is connected with power supply through second frequency converter and first circuit breaker;First frequency converter and second frequency converter are connected with the PLC controller respectively;The controller is connected with man-machine interaction module.The utility model is a kind of vacuum pump frequency conversion control system based on PLC, realize accurate frequency conversion control to screw rod pump and Roots pump, guarantee motor safe operation, adapt to different load working condition, meet the use demand of dangerous area simultaneously, solve frequency interference problem.

Description

Technical Field

[0001] This utility model relates to the field of control, specifically a frequency conversion control system for vacuum equipment based on PLC. Background Technology

[0002] In industrial production, vacuum pumps are key equipment for creating a vacuum environment. Their operational stability, control precision, and adaptability to different working conditions directly affect production efficiency and product quality. Traditional vacuum pump control systems often use custom circuit boards. This approach suffers from fixed control logic, poor flexibility, difficulty in adjusting pump speed according to actual working conditions, and a lack of effective overload and overcurrent protection for the motor, making the equipment susceptible to damage from sudden malfunctions.

[0003] Meanwhile, in hazardous areas such as oil and chemical plants, ordinary control cabinets lack explosion-proof capabilities and cannot be used directly, requiring additional explosion-proof isolation facilities, which increases equipment investment costs and floor space. Furthermore, traditional control systems are susceptible to electromagnetic interference in variable frequency environments, leading to large data acquisition deviations and delayed control command execution. Moreover, when operating in a sealed cabinet, the heat generated by the equipment is difficult to dissipate, and prolonged high-temperature operation shortens component lifespan and reduces system reliability.

[0004] To address the aforementioned issues, there is an urgent need for a vacuum pump control system that possesses high stability, strong anti-interference capabilities, adaptability to various load conditions, and meets the requirements for use in hazardous areas. As a result, the PLC-based vacuum pump frequency conversion control system has emerged. Utility Model Content

[0005] Therefore, the purpose of this utility model is to overcome the shortcomings of existing vacuum pump control systems in terms of stability, flexibility, explosion-proof performance, anti-interference and heat dissipation, and to provide a PLC-based vacuum pump frequency conversion control system that can achieve precise frequency conversion control of screw pumps and Roots pumps, ensure the safe operation of motors, adapt to different load conditions, meet the needs of use in hazardous areas, and solve the problem of frequency conversion interference.

[0006] Specifically, a PLC-based frequency conversion control system for vacuum equipment, the vacuum equipment including a screw pump and a Roots pump, the control system including a first frequency converter, a second frequency converter, and a PLC controller; The screw pump is connected to the power supply via a first frequency converter and a first circuit breaker. The Roots pump is connected to the power supply via a second frequency converter and a first circuit breaker. The first frequency converter and the second frequency converter are respectively connected to the PLC controller; The controller is connected to a human-machine interaction module.

[0007] The control system also includes a digital control module and an analog control module connected to the PLC controller.

[0008] Optionally, the housing of the vacuum equipment is a positive pressure explosion-proof housing, and the housing material is 304 stainless steel with a thickness of not less than 2mm.

[0009] Optionally, the housing has at least one positive pressure chamber for mounting the PLC controller, frequency converter, and low-voltage components.

[0010] Optionally, the connecting surfaces of the components of the housing adopt a stop structure.

[0011] This utility model has the following advantages: This utility model is a PLC-based vacuum pump frequency conversion control system that enables precise frequency conversion control of screw pumps and Roots pumps, ensures safe motor operation, adapts to different load conditions, meets the needs of use in hazardous areas, and solves the problem of frequency conversion interference. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the module structure of the PLC-based frequency conversion control system for vacuum equipment described in this utility model; Figure 2 This is the main circuit diagram of the PLC-based frequency conversion control system for vacuum equipment described in this utility model; Figure 3 This is a schematic diagram of the housing structure of the vacuum device described in this utility model; Figure 4 This is a schematic diagram of the stop structure; In the diagram: 100, housing; 200, PLC controller; 300, relay; 400, frequency converter; 500, stop structure. Detailed Implementation

[0013] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0014] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0015] As described in the background section, in hazardous areas such as petroleum and chemical plants, ordinary control cabinets lack explosion-proof capabilities and cannot be used directly. Additional explosion-proof isolation facilities must be constructed, increasing equipment investment costs and floor space requirements. Furthermore, traditional control systems are susceptible to electromagnetic interference in variable frequency environments, leading to large data acquisition deviations and delayed control command execution. Moreover, when operating in a sealed cabinet, the heat generated by the equipment is difficult to dissipate, and prolonged high-temperature operation shortens component lifespan and reduces system reliability.

[0016] Based on the above issues, such as Figures 1-4 As shown, this embodiment provides a PLC-based frequency conversion control system for vacuum equipment. The vacuum equipment includes a screw pump and a Roots pump. The control system includes a first frequency converter, a second frequency converter, and a PLC controller. The screw pump is connected to the power supply via a first frequency converter and a first circuit breaker. The Roots pump is connected to the power supply via a second frequency converter and a first circuit breaker. The first frequency converter and the second frequency converter are respectively connected to the PLC controller; The controller is connected to a human-machine interaction module.

[0017] The control system also includes a digital control module and an analog control module connected to the PLC controller.

[0018] For example, firstly, a switching power supply with excellent isolation performance is used to power the PLC controller and control module, which can effectively block external power grid interference and common-mode interference generated by the frequency converter; secondly, the power cable between the frequency converter and the motor is a shielded cable, and the shielding layer is grounded at both ends (grounding resistance ≤4Ω) to reduce the outward propagation of electromagnetic radiation; at the same time, the control cable between the PLC controller and the frequency converter is a twisted pair cable laid in a metal conduit, and the metal conduit is grounded to enhance the resistance to external electromagnetic interference; in addition, an RC filter circuit (capacitor 104μF, resistor 100Ω) is connected in parallel at the input and output ports of the PLC controller and the signal terminals of the analog control module to reduce the impact of high-frequency interference signals on the equipment.

[0019] When connecting the power supply, connect the 380V three-phase AC power to the explosion-proof terminal block of the explosion-proof cabinet. After passing through the explosion-proof circuit breaker, the power is split into two paths. One path is connected to the switching power supply (output 24V DC) to power the PLC controller (exemplary model: Siemens S7-1200 CPU 1214C), digital control module (exemplary model: SM 1223), analog control module (exemplary model: SM 1234), temperature sensor, and vacuum sensor. The other path is connected to the frequency converter 400 (exemplary model: ABBACS510) to power the frequency converter.

[0020] When connecting control signals, the digital output ports (Q0.0, Q0.1) of the PLC controller are connected to the start / stop control terminals (DI1, DI2) of the frequency converter, respectively, to control the start and stop of the frequency converter; the analog output port (AQ0.0) of the PLC controller is connected to the speed command terminal (AI1) of the frequency converter through a shielded cable, to output a 0-10V speed command signal; the analog feedback port (AO1) of the frequency converter is connected to the analog input port (AI0.0) of the PLC, to provide feedback on the output frequency of the frequency converter; the vacuum sensor (output 4-20mA) is connected to the AI1 port of the analog control module, and the motor temperature sensor (output 0-10V) is connected to the AI2 port of the analog control module; the DI0-DI3 ports of the digital control module are connected to the vacuum pump start / stop status contact, the cabinet door switch contact, the frequency converter fault contact, and the system emergency stop button, respectively.

[0021] When connecting the motors of the screw pump and the Roots pump, the output terminals (U, V, W) of the frequency converter are connected to the screw pump motor and the Roots pump motor (motor power is 7.5kW and 15kW respectively) through shielded power cables, and the two ends of the cable shield are grounded; at the same time, a surge protector is installed at the motor power supply end to prevent the frequency converter output voltage fluctuation from impacting the motor.

[0022] In this embodiment, the PLC controller, as the core decision-making and control unit of the control system, adopts a high-performance processor and possesses powerful data processing and logic operation capabilities. Through real-time data interaction with digital and analog control modules, it accurately collects system operating parameters (such as pump speed, motor current, voltage, vacuum level, etc.) and outputs precise control signals to the frequency converter according to preset control logic or user instructions, thereby achieving real-time regulation of the vacuum pump's operating status.

[0023] Meanwhile, the PLC controller has excellent anti-interference performance. Through the electromagnetic shielding design at the hardware level, it can effectively resist electromagnetic interference in the industrial field, ensure the accuracy of data acquisition and the reliable execution of control commands, significantly improve the overall stability of the system, and avoid control failure or equipment failure caused by interference.

[0024] The first and second frequency converters serve as key execution units connecting the PLC controller 200 and the vacuum pump motor. They receive control signals (such as analog voltage / current signals or digital communication signals) output by the PLC controller 200 and convert the industrial frequency AC power into AC power with adjustable frequency and voltage through the internal power conversion circuit, thereby controlling the speed of the screw pump and Roots pump motors.

[0025] In terms of speed control, the first and second frequency converters can smoothly adjust the motor speed according to the vacuum requirement or load signal transmitted by the PLC controller. For example, when the vacuum degree does not reach the target value, the motor speed is gradually increased to improve the vacuuming efficiency; after the vacuum degree stabilizes, the speed is reduced to save energy and achieve on-demand energy supply.

[0026] In terms of motor protection, the frequency converter has built-in protection functions such as overcurrent, overload, overvoltage, undervoltage, phase loss, and overheating. It monitors the motor operating parameters in real time. When the detected parameters exceed the safety threshold, it immediately cuts off the output or sends an alarm signal and feeds the fault information back to the PLC controller. The PLC controller then triggers corresponding protection actions (such as shutdown and audible and visual alarms), effectively preventing the motor from being damaged due to abnormal operating conditions and extending the motor's service life.

[0027] In this embodiment, the digital signal control module is mainly responsible for acquiring switching signals in the system, such as the start / stop status of the vacuum pump, the open / closed status of the cabinet door, and fault alarm contact signals. Simultaneously, it receives digital control commands output by the PLC controller to control the on / off state of external actuators (such as indicator lights, relays 300, alarm devices, etc.). This module possesses highly reliable signal isolation capabilities to prevent external signals from interfering with the internal circuitry of the system, ensuring the accuracy and security of switching signal transmission.

[0028] In this embodiment, the analog control module is used to acquire continuously changing analog signals, such as the 4-20mA current signal output by the vacuum sensor, the 0-10V voltage signal output by the motor temperature sensor, and the frequency feedback signal output by the frequency converter, and converts these analog signals into digital signals that the PLC controller can recognize. Simultaneously, it converts the control commands output by the PLC controller (such as the frequency converter speed command signal) into analog signals and transmits them to the frequency converter. The module uses high-precision A / D (analog-to-digital) and D / A (digital-to-analog) conversion chips with a conversion accuracy of up to 0.1%, ensuring the accuracy of analog data acquisition and control command transmission, and providing data support for the system's fine control.

[0029] In one embodiment, the PLC controller is also connected to a CPU (Central Processing Unit). The CPU, as the core computing unit of the PLC controller, undertakes the critical tasks of system data processing, logical judgment, and instruction execution. It adopts a high-speed multi-core processor architecture, with a computing speed of up to millions of instructions per second. It can quickly process massive amounts of data collected by digital and analog control modules, analyze user-preset control programs in real time (such as load mode switching logic, fault handling procedures, vacuum closed-loop control algorithms, etc.), and rapidly generate control instructions to send to the frequency converter and other actuators.

[0030] In addition, the CPU is equipped with a variety of communication interfaces (such as RS485, Profinet, etc.), which can realize high-speed data interaction with devices such as frequency converters, upper-level monitoring systems, and sensors. It supports real-time data uploading and remote control command reception, providing a hardware foundation for intelligent management and remote monitoring of the system, and ensuring the efficient and orderly operation of the entire control system.

[0031] To meet the usage requirements of hazardous areas such as petroleum and chemical industries (e.g., Zone 2 explosive gas atmospheres), the cabinet in this embodiment adopts an explosion-proof design and complies with GB 3836.1-2021 "Explosive Atmospheres - Part 1: Equipment - General Requirements" and GB 3836.5-2021 "Explosive Atmospheres - Part 5: Equipment Protected by a Positive Pressure Enclosure 'p'" standards.

[0032] This positive pressure explosion-proof cabinet's main body shell 100 is also made of 304 stainless steel with excellent mechanical strength, and a thickness of not less than 2mm. This not only provides solid physical protection for the critical internal equipment, but also forms the basis for establishing and maintaining an effective protective positive pressure environment. The shell has at least one positive pressure chamber for installing PLC controllers, frequency converters, and low-voltage components. The connection surfaces of all components of the shell adopt a stop-lock structure (e.g., ...). Figure 4 The term "stop structure" (referring to the stop structure in section 500) refers to a structure with a protrusion on one side and a groove on the other side that matches the protrusion. Figure 4 As shown.

[0033] When the cabinet is in operation, clean compressed air or inert gas must be continuously introduced into the sealed shell. Through an automatic adjustment system, the internal pressure is kept consistently higher than the external atmospheric pressure (usually ≥150Pa), which effectively prevents the external explosive gas mixture from entering the cabinet, thereby eliminating the possibility of an explosion caused by electric arcs or sparks generated by internal components.

[0034] After the positive pressure system successfully ventilates and establishes a stable pressure, all electrical components installed in the cabinet, such as the frequency converter and PLC controller, are actually operating normally in a safe, "non-hazardous" environment. For heat dissipation and electromagnetic compatibility considerations, high-power heat-generating components and low-voltage sensitive components are arranged in separate zones.

[0035] Meanwhile, to ensure the stable operation of the positive pressure system and to facilitate heat dissipation, the enclosure is equipped with a special positive pressure ventilation device. This device integrates functions such as pressure release and gas flow, ensuring that while maintaining stable internal pressure, it can safely expel hot air from the cabinet and prevent any sparks generated inside the cabinet from escaping outside.

[0036] The enclosure described in this embodiment can be directly installed and used in hazardous areas such as petroleum refining workshops and chemical reaction zones. This explosion-proof enclosure eliminates the need for additional explosion-proof isolation rooms, significantly reducing equipment installation space and investment costs. Its explosion-proof performance is stable, allowing for long-term operation in ambient temperatures ranging from -40℃ to +60℃ and relative humidity ≤95% (non-condensing), making it suitable for harsh industrial environments.

[0037] Furthermore, the cabinet surface is coated with an electrostatic spraying process, providing excellent corrosion resistance and protecting against acid and alkali gases in chemical environments. This allows operators to observe the system's operating status without opening the cabinet door, while also preventing static electricity generated when the door is opened from igniting explosive gases, ensuring operational safety. In the vacuum system of a styrene storage tank at a petrochemical plant, this explosion-proof cabinet has achieved five consecutive years of accident-free operation, verifying its reliability in hazardous areas.

[0038] The PLC-based variable frequency control system for vacuum equipment described in this invention collects or outputs data through four parts: a data acquisition module, a mode control module, a fault handling module, and a communication module. The data acquisition module collects and filters parameters such as vacuum level, motor temperature, inverter output frequency, and equipment status. The mode control module calculates the inverter speed setpoint based on the user-selected load mode (light load, medium load, high load) or vacuum level requirement and outputs a control signal. The fault handling module monitors system fault signals in real time (such as inverter failure, motor over-temperature, and abnormal vacuum level) and triggers corresponding protection actions (shutdown, alarm, and fault code recording). The communication module enables data interaction between the PLC controller and the inverter (using the Modbus RTU protocol) and the upper-level monitoring system (using the Profinet protocol).

[0039] When setting the inverter parameters, configure the parameters through the inverter operation panel. Set the inverter control mode to "external analog control" and the speed command signal type to "0-10V voltage signal". Set the motor parameters (rated power, rated voltage, rated current, rated speed) to match the parameters of the screw pump and Roots pump motors. Set the protection parameters (overcurrent protection value is 1.2 times the rated current of the motor, overload protection time is 60s, and overtemperature protection value is 85℃). At the same time, set the inverter carrier frequency to 8kHz to reduce electromagnetic radiation interference.

[0040] Meanwhile, during human-machine interaction, the HMI (Human-Machine Interface) module is used: This HMI uses a Kunlun Tongtai TPC1061Ti touch screen as the HMI, which is connected to the PLC controller via Ethernet. The interface design includes a system operation status monitoring page (displaying vacuum level, motor speed, cabinet temperature, and equipment status), a load mode selection page (light load / medium load / high load mode switching button), a parameter setting page (settings for vacuum target value, speed upper and lower limits, and temperature alarm threshold), and a fault query page (fault codes and fault time records), which is convenient for operators to monitor in real time.

[0041] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A PLC-based frequency conversion control system for vacuum equipment, characterized in that: The vacuum equipment includes screw pumps and Roots pumps, and the control system includes a first frequency converter, a second frequency converter, and a PLC controller; The screw pump is connected to the power supply via a first frequency converter and a first circuit breaker. The Roots pump is connected to the power supply via a second frequency converter and a first circuit breaker. The first frequency converter and the second frequency converter are respectively connected to the PLC controller; The controller is connected to a human-machine interaction module.

2. The PLC-based frequency conversion control system for vacuum equipment according to claim 1, characterized in that: It also includes digital control modules and analog control modules that connect to the PLC controller.

3. The PLC-based frequency conversion control system for vacuum equipment according to claim 1, characterized in that: The outer shell of the vacuum equipment is a positive pressure explosion-proof shell, and the shell material is 304 stainless steel with a thickness of not less than 2mm.

4. The PLC-based frequency conversion control system for vacuum equipment according to claim 3, characterized in that: The housing has at least one positive pressure chamber for mounting the PLC controller, frequency converter, and low-voltage components.

5. The PLC-based frequency conversion control system for vacuum equipment according to claim 3, characterized in that: The connecting surfaces of the various components of the outer shell adopt a stop structure.

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