A variable frequency cabinet control device and system

Abstract

The application relates to the field of variable frequency cabinet control, in particular to a variable frequency cabinet control device and system. The device comprises: a first input end of a first intermediate relay is used for being connected with a third phase voltage; output ends of the first intermediate relay are connected with a first input end, a second digital input interface and a third digital input interface of a second intermediate relay respectively; output ends of the second intermediate relay are connected with a first digital input interface and a zero line respectively; an input end of a mode switching switch is used for being connected with the third phase voltage; an output end of the mode switching switch is connected with the zero line; a frequency converter in the variable frequency cabinet is connected with a centralized control cabinet through an RS485 communication line. The device is used for flexibly switching the control mode between the local and the remote, and reduces the cost and complexity of controlling the variable frequency cabinet.

Description

Technical Field

[0001] This utility model relates to the field of frequency converter cabinet control, and more specifically, to a frequency converter cabinet control device and system. Background Technology

[0002] Variable frequency drive (VFD) cabinets, as control devices for VFDs, regulate the operating frequency of AC motors in HVAC systems. They are widely used in critical equipment such as cooling towers, main units, and chilled water pumps in chiller rooms and terminal air handling units. To balance the dual goals of improving HVAC system energy efficiency and reducing operating costs, their control strategies must meet the flexibility requirements of quickly starting AC motors during commissioning, while also ensuring basic operational safety through manual operation should a failure occur in control equipment including the VFD cabinet. Currently, the industry commonly adopts a dual-mode architecture of local and remote control: local control relies on the VFD cabinet's control panel for direct manual intervention, while remote control uses a centralized control cabinet equipped with a programmable logic controller (PLC) for parameterized command transmission. However, traditional connection methods require deploying six 2-core cables between the central control cabinet and the frequency converter cabinet to transmit six types of key information, including start-up status, alarm signals, local / remote operating modes, operating frequency feedback, and given frequency commands. This necessitates configuring multiple types of input and output (I / O) interfaces, including analog and digital input and output modules, in both the central control cabinet and the frequency converter cabinet. As the number of frequency converter cabinets requiring centralized control continues to increase, this hard-wiring method significantly drives up hardware costs and construction complexity. Although the industry has attempted to simplify the control circuitry with only one RS485 communication line, it can only achieve basic remote communication control functions for PLC, such as start / stop and speed / frequency adjustment. It cannot achieve the function of detecting and switching between local and remote modes in conjunction with the PLC, revealing significant limitations: when the PLC or communication link fails, not only is seamless switching between local and remote control impossible, but the loss of emergency manual operation capability also exacerbates the risk of loss of control. Utility Model Content

[0003] This utility model provides a frequency converter cabinet control device and system for realizing flexible switching between local control and remote control, reducing the cost and complexity of controlling the frequency converter cabinet.

[0004] According to a first aspect of this application, a variable frequency drive (VFD) cabinet control device is provided, the VFD cabinet comprising a VFD and a mode switching switch, the device comprising: The first input terminal of the first intermediate relay is used to connect to the third phase voltage in the three-phase power supply, and the first output terminal of the first intermediate relay is connected to the first input terminal of the second intermediate relay. The first output terminal of the second intermediate relay is connected to the first digital input interface of the frequency converter, and the second output terminal of the second intermediate relay is connected to the neutral wire. The second output terminal of the first intermediate relay is connected to the second digital input interface of the frequency converter, and the third output terminal of the first intermediate relay is connected to the third digital input interface of the frequency converter. The second input terminal of the first intermediate relay and the second input terminal of the second intermediate relay are respectively connected to the first output voltage interface of the frequency converter; The input terminal of the mode switching switch is used to connect to the third phase voltage in the three-phase power supply, and the output terminal of the mode switching switch is connected to the neutral line. The first phase voltage input interface of the frequency converter is used to connect to the first phase voltage of the three-phase power supply, the second phase voltage input interface of the frequency converter is used to connect to the second phase voltage of the three-phase power supply, and the third phase voltage input interface of the frequency converter is used to connect to the third phase voltage of the three-phase power supply. The first phase voltage output interface, the second phase voltage output interface and the third phase voltage output interface in the frequency converter are respectively used to connect to the AC motor circuit; The positive RS485 interface of the frequency converter is connected to the positive RS485 communication line, which is used to connect to the positive RS485 interface of the central control cabinet. The negative RS485 interface of the frequency converter is connected to the negative RS485 communication line, which is used to connect to the negative RS485 interface of the central control cabinet. The positive and negative RS485 communication lines are also connected to the first analog ground interface.

[0005] Understandably, the design of the first and second intermediate relays ensures both the reliable execution of start / stop commands from the frequency converter cabinet and the flexible configuration of multi-channel control signals. The RS485 communication bus establishes a communication link between the control cabinet and the frequency converter; a single 2-core RS485 communication cable can carry the dual functions of AC motor status monitoring and operation command issuance, significantly reducing the construction complexity and electromagnetic interference risks associated with traditional hardwiring.

[0006] Optionally, the frequency converter cabinet also includes a control panel, which is connected to the frequency converter.

[0007] Understandably, by connecting the integrated control panel and the frequency converter, an efficient human-machine interface is created, enabling operators to conveniently input control commands and significantly improving operational flexibility and response speed.

[0008] Optionally, the control panel is equipped with a local frequency adjustment potentiometer; The second output voltage interface of the frequency converter is connected to the input terminal of the local frequency adjustment potentiometer. The first output terminal of the local frequency adjustment potentiometer is connected to the frequency input interface of the frequency converter. The second output terminal of the local frequency adjustment potentiometer is connected to the second analog ground interface of the frequency converter.

[0009] Understandably, by deeply integrating the local frequency adjustment potentiometer into the inverter's output voltage interface, a self-sufficient analog closed-loop regulation circuit is constructed, enabling operators to directly and smoothly adjust the AC motor's operating frequency. This significantly reduces hardware costs and construction complexity, greatly improves frequency regulation accuracy and stability, and provides an economical, efficient, and reliable human-machine interaction experience for operation and maintenance.

[0010] Optionally, the control panel is provided with a local start button; The fourth output terminal of the first intermediate relay is connected to the input terminal of the local start button, and the output terminal of the local start button is connected to the neutral wire.

[0011] Understandably, by forming a control loop between the local start button and the first intermediate relay, safe and reliable start-stop operations are achieved. This ensures that operators can immediately trigger the local start button to run the frequency converter in emergency situations without relying on remote control commands. This significantly improves the response speed of local control and the overall stability of the device, and greatly reduces the complexity of operation and maintenance and potential faults in distributed control scenarios.

[0012] Optionally, the control panel is provided with a local stop button; The fourth output terminal of the first intermediate relay is connected to the input terminal of the local stop button, and the output terminal of the local stop button is connected to the neutral wire.

[0013] Understandably, by connecting the local stop button to the control circuit of the first intermediate relay, the operator can immediately interrupt operation to deal with emergencies. While maintaining the original centralized control function, the local emergency response efficiency is greatly enhanced, enabling the device to have both the rapid intervention capability required in industrial sites and the collaborative advantages of centralized management, ultimately achieving dual optimization of safety boundaries and operation and maintenance efficiency in the distributed control system.

[0014] Optionally, the control panel is provided with a local start button and a local stop button; The fourth output terminal of the first intermediate relay is connected to the input terminal of the local start button, and the output terminal of the local start button is connected to the input terminal of the local stop button. The output terminal of the local stop button is connected to the neutral wire.

[0015] Understandably, by connecting the local start button and the local stop button to the control circuit of the first intermediate relay, safe and reliable start and stop operations are achieved. This not only standardizes the operation sequence and effectively prevents AC motor malfunctions or safety accidents caused by accidental touches, but also improves the real-time response capability and operational stability of local control.

[0016] Optionally, the control panel is equipped with a running indicator light; The inverter's operating signal voltage input interface is used to connect to the third phase voltage of the three-phase power supply, the inverter's operating signal output interface is connected to the input terminal of the operating indicator light, and the neutral wire is connected to the output terminal of the operating indicator light.

[0017] Understandably, by forming a closed-loop path with the operation indicator light, the inverter's operation signal interface, and the third phase voltage of the three-phase power supply, real-time, accurate, and visual feedback on the AC motor's operating status is achieved. This provides operators with intuitive and reliable status indications to avoid the risk of misoperation, enhances local safety monitoring capabilities, and significantly reduces the complexity of operation and maintenance and the difficulty of troubleshooting the control device.

[0018] Optionally, the control panel is equipped with a fault indicator light; The fault signal voltage input interface of the frequency converter is used to connect to the third phase voltage of the three-phase power supply, the fault signal output interface of the frequency converter is connected to the input terminal of the fault indicator light, and the output terminal of the fault indicator light is connected to the neutral wire.

[0019] Understandably, by constructing a closed-loop path with the fault indicator light, the inverter fault signal interface, and the third phase voltage of the three-phase power supply, real-time, accurate, and visual feedback of AC motor fault status is achieved. This provides operators with intuitive and reliable on-site fault indications to accelerate emergency response and effectively avoid the risk of secondary accidents. In this way, while strengthening local safety monitoring capabilities, the complexity of fault diagnosis and maintenance costs of the equipment are significantly reduced, and the operational efficiency and reliability of the industrial site are comprehensively improved.

[0020] According to a second aspect of this application, a frequency converter cabinet control system is provided, the system including a central control cabinet and a frequency converter cabinet control device using the method described in the first aspect, wherein the RS485 communication positive line is connected to the RS485 positive terminal interface of the central control cabinet, and the RS485 communication negative line is connected to the RS485 negative terminal interface of the central control cabinet.

[0021] Optionally, the frequency converter cabinet control device includes several frequency converter cabinets. The RS485 positive terminals of the frequency converters in the several frequency converter cabinets are all connected to the RS485 positive terminal of the central control cabinet through the same RS485 communication positive line. The RS485 negative terminals of the corresponding frequency converters in the several frequency converter cabinets are all connected to the RS485 negative terminal of the central control cabinet through the same RS485 communication negative line.

[0022] Understandably, by efficiently interconnecting the central control cabinet with multiple frequency converter control devices via the RS485 communication bus, a seamless integration of centralized monitoring and distributed management is achieved. This significantly reduces the wiring complexity, material and labor costs associated with traditional wiring methods, while also eliminating the need for extensive hardware investment in input / output modules for the central control cabinet. As a result, the overall economy and operational reliability are greatly optimized while improving the scalability and ease of operation and maintenance of the control system.

[0023] Based on any of the above aspects, the frequency converter control device and system provided in this application embodiment can achieve the following effects: Through the synergistic application of integrated circuit design, RS485 communication technology, and inverter function parameter settings, seamless switching and centralized management of local and remote dual-mode control are achieved. While retaining the original safety control architecture, the performance of the inverter cabinet control device and system is significantly optimized. The adoption of a single 2-core RS485 communication bus to replace the traditional multi-path wiring method enables the central control cabinet to control multiple inverter cabinets in parallel, greatly reducing cable laying costs and construction complexity. It is especially suitable for long-distance transmission scenarios to effectively avoid the risks of analog signal attenuation and electromagnetic interference. By reconstructing the relay logic circuit and coordinating it with the inverter's digital and analog interfaces, the local control panel's start / stop operation, frequency adjustment, and status indication functions are maintained. The central control cabinet can also achieve remote control via the RS485 communication bus, thus completely eliminating the need for corresponding input / output module hardware investment in the central control cabinet. This not only reduces the size and manufacturing cost of the control device and system but also simplifies the control connection by using the RS485 communication bus. This allows maintenance personnel to monitor AC motors simply through the local control panel or the central control cabinet, greatly reducing the probability of failures caused by wiring errors. Ultimately, this improves the high reliability, low-cost operation and maintenance, and strong scalability of the control inverter cabinet. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1This is a circuit diagram of a frequency converter cabinet control device provided in this embodiment.

[0026] Figure 2 This is a schematic diagram of the control panel of a frequency converter cabinet control device provided in this embodiment.

[0027] Figure 3 This embodiment provides a schematic diagram of a frequency converter cabinet control system.

[0028] Icons: 100, Variable Frequency Cabinet; 110, Variable Frequency Drive; 120, Control Panel; 200, Centralized Control Cabinet; L1, First Phase Voltage of Three-Phase Power Supply; L2, Second Phase Voltage of Three-Phase Power Supply; L3, Third Phase Voltage of Three-Phase Power Supply; QF1, First Circuit Breaker; QF2, Second Circuit Breaker; QF3, Third Circuit Breaker; S1, Mode Switch; N, Neutral Wire; KA1, First Intermediate Relay; KA2, Second Intermediate Relay; DI1, First Digital Input Interface; DI2, Second Digital Input Interface; DI3, Third Digital Input Interface; +24V, First Output Voltage Interface; U1, First Phase Voltage Input Interface; V1, Second Phase Voltage Input Interface; W1, Third Phase Voltage Input Interface; U2, First Phase Voltage Output Interface; V2... Second phase voltage output interface; W2, third phase voltage output interface; M2, AC motor circuit; 485+, RS485 positive terminal interface; 485-, RS485 negative terminal interface; A2, RS485 communication positive line; B2, RS485 communication negative line; AGND1, first analog ground interface; RP1, local frequency adjustment potentiometer; +10V, second input voltage interface; AI1, frequency input interface; AGND2, second analog ground interface; SB1 - local start button; SB2 - local stop button; H1, running indicator light; DO11, running signal voltage input interface; DO12, running signal output interface; H2, fault indicator light; DO21, fault signal voltage input interface; DO22, fault signal output interface. Detailed Implementation

[0029] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this application. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0030] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] Traditional frequency converter cabinets rely on hard-wiring to transmit various signals between the frequency converter cabinet and the central control cabinet, resulting in high hardware costs and complex construction. On the other hand, RS485-based communication solutions are prone to losing local and remote control switching capabilities due to link failures, posing a safety risk of emergency operation failure.

[0033] This embodiment provides a technical solution that can solve the above problems. The specific implementation of this application will be described in detail below with reference to the accompanying drawings.

[0034] like Figure 1 As shown, this embodiment provides a frequency converter cabinet control device. The frequency converter cabinet 100 includes a frequency converter 110 and a mode switching switch S1. The device includes: The first input terminal of the first intermediate relay KA1 is used to connect to the third phase voltage L3 in the three-phase power supply, and the first output terminal of the first intermediate relay KA1 is connected to the first input terminal of the second intermediate relay KA2. The first output terminal of the second intermediate relay KA2 is connected to the first digital input interface DI1 of the frequency converter 110, and the second output terminal of the second intermediate relay KA2 is connected to the neutral line N. The second output terminal of the first intermediate relay KA1 is connected to the second digital input interface DI2 of the frequency converter 110, and the third output terminal of the first intermediate relay KA1 is connected to the third digital input interface DI3 of the frequency converter 110. The second input terminal of the first intermediate relay KA1 and the second input terminal of the second intermediate relay KA2 are respectively connected to the first output voltage interface +24V of the inverter 110; The input terminal of the mode switching switch S1 is used to connect to the third phase voltage L3 in the three-phase power supply, and the output terminal of the mode switching switch S1 is connected to the neutral line N. The first phase voltage input interface U1 of the inverter 110 is used to connect to the first phase voltage L1 in the three-phase power supply, the second phase voltage input interface V1 of the inverter 110 is used to connect to the second phase voltage L2 in the three-phase power supply, and the third phase voltage input interface W1 of the inverter 110 is used to connect to the third phase voltage L3 in the three-phase power supply. The first phase voltage output interface U2, the second phase voltage output interface V2 and the third phase voltage output interface W2 in the frequency converter 110 are respectively used to connect to the AC motor circuit M1. The positive RS485 interface 485+ of the frequency converter 110 is connected to the positive RS485 communication line A2. The positive RS485 communication line A2 is used to connect to the positive RS485 interface of the central control cabinet 200. The negative RS485 interface of the frequency converter 110 is connected to the negative RS485 communication line B2. The negative RS485 communication line B2 is used to connect to the negative RS485 interface of the central control cabinet 200. The positive and negative RS485 communication lines are also connected to the first analog ground interface AGND1.

[0035] Specifically, such as Figure 2 As shown, the frequency converter cabinet 100 also includes a control panel 120, which is connected to the frequency converter 110.

[0036] Specifically, the control panel 120 is equipped with a local frequency adjustment potentiometer RP1; The second output voltage interface +10V of the frequency converter is connected to the input terminal of the local frequency adjustment potentiometer RP1; The first output terminal of the local frequency adjustment potentiometer RP1 is connected to the frequency input interface AI1 of the frequency converter 110; The second output terminal of the local frequency adjustment potentiometer RP1 is connected to the second analog ground interface AGND2 of the frequency converter 110.

[0037] Preferably, the local frequency adjustment potentiometer RP1 is connected in series with the second output voltage interface of the frequency converter at +10V. The operator can adjust the input voltage through the local frequency adjustment potentiometer to obtain a variable local frequency. Preferably, the local frequency adjustment potentiometer RP1 can be a potentiometer.

[0038] Preferably, the mode switching switch is located in the control panel.

[0039] Specifically, the control panel 120 is equipped with a local start button SB1; The fourth output terminal of the first intermediate relay KA1 is connected to the input terminal of the local start button SB1, and the output terminal of the local start button SB1 is connected to the neutral line N.

[0040] Specifically, the control panel is equipped with a local stop button SB2; The fourth output terminal of the first intermediate relay KA1 is connected to the input terminal of the local stop button SB2, and the output terminal of the local stop button SB2 is connected to the neutral line N.

[0041] In another embodiment, the control panel 120 is provided with a local start button SB1 and a local stop button SB2; The fourth output terminal of the first intermediate relay KA1 is connected to the input terminal of the local start button SB1, and the output terminal of the local start button SB1 is connected to the input terminal of the local stop button SB2. The output terminal of the local stop button SB2 is connected to the neutral line N.

[0042] Specifically, the control panel 120 is equipped with a running indicator light H1; The inverter 110's operating signal voltage input interface DO11 is used to connect to the third phase voltage L3 of the three-phase power supply, the inverter 110's operating signal output interface DO12 is connected to the input terminal of the operating indicator H1, and the output terminal of the operating indicator H1 is connected to the neutral line N.

[0043] Specifically, the control panel 120 is equipped with a fault indicator light H2; The fault signal voltage input interface DO21 of the frequency converter 110 is used to connect to the third phase voltage L3 of the three-phase power supply, and the fault signal output interface DO22 of the frequency converter 110 is connected to the input terminal of the fault indicator H2. The output terminal of the fault indicator H2 is connected to the neutral line N.

[0044] During actual operation of the frequency converter cabinet 100, the operator can select the control mode of the frequency converter cabinet 100 using the mode switching switch S1 on the control panel 120. When the mode switching switch S1 is closed, the control mode of the frequency converter cabinet 100 is the local control mode, and the operator can control the frequency converter cabinet 100 through the control panel 120. When the mode switching switch S1 is open, the operating mode of the frequency converter cabinet 100 is switched to the remote control mode, and the operator cannot control the frequency converter cabinet 100 through the control panel 120. Instead, the operator can control the frequency converter cabinet 100 remotely through the central control cabinet 200 via an RS485 communication line.

[0045] When the mode switching switch S1 is closed, the operating mode of the frequency converter cabinet 100 is local control mode: When the operator triggers the local start button SB1, the first intermediate relay KA1 and the second intermediate relay KA2 are energized in the circuit, forming a loop. The first intermediate relay KA1 transmits the local control mode command to the inverter 100 through the second digital input interface DI2 in the inverter 110, and transmits the local control frequency command to the inverter 100 through the third digital input interface DI3 in the inverter 100. After the inverter obtains the local control mode command and the local control frequency command from the first intermediate relay KA1 through the second digital input interface DI2 and the third digital input interface DI3, it can obtain... It is known that relevant instructions need to be obtained from the local source, including obtaining the local control start instruction from the first digital input interface DI1 and obtaining the local frequency from the local frequency adjustment potentiometer RP1 in the control panel 120. Preferably, the operator can control the given local frequency by toggling the local frequency adjustment potentiometer RP1. After the second intermediate relay KA2 is energized, it transmits the local control start instruction to the frequency converter 110 through the first digital input interface DI1 in the frequency converter 110. After receiving the local control start instruction, the frequency converter 110 can drive the AC motor based on the local control start instruction and the obtained local frequency.

[0046] If the AC motor circuit M1 is operating normally, the running indicator H1 will turn on; if the AC motor circuit M1 malfunctions, the fault indicator H2 will turn on.

[0047] When the operator triggers the local stop button SB2, the frequency converter 110 no longer supplies power to the AC motor circuit M1, and can control the AC motor in the AC motor circuit M1 to stop.

[0048] When the mode switch S1 is open, the inverter cabinet 100 operates in remote control mode. The first intermediate relay KA1 and the second intermediate relay KA2 are de-energized. The second digital input interface DI2 and the third digital input interface DI3 of the inverter 110 generally cannot receive local control commands from KA1, and the first digital input interface DI1 generally cannot receive local control start commands from KA2. The operator also cannot control the AC motor circuit M1 in the control panel 120, such as starting, stopping, and setting the frequency. At this time, the central control cabinet 200 can control the inverter 110 via the RS485 communication line.

[0049] The RS485 communication line can receive the operating status of the AC motor from the operation signal output interface DO12 and the fault signal output interface DO22, and transmit it to the central control cabinet 200, so that the central control cabinet 200 can obtain the operating status of the AC motor in real time.

[0050] like Figure 3 As shown in the figure, this application embodiment also provides a frequency converter cabinet control system. Optionally, the system includes a central control cabinet 200 and a frequency converter cabinet control device as described above, wherein the RS485 communication positive line A2 is connected to the RS485 positive terminal interface of the central control cabinet 200, and the RS485 communication negative line B2 is connected to the RS485 negative terminal interface of the central control cabinet 200.

[0051] Specifically, the frequency converter cabinet control device includes several frequency converter cabinets 100. The RS485 positive terminal interface 485+ of the frequency converters 110 in the several frequency converter cabinets 100 are all connected to the RS485 positive terminal interface of the central control cabinet 200 through the same RS485 communication positive line A2. The RS485 negative terminal interface 485- of the corresponding frequency converters in the several frequency converter cabinets 100 are all connected to the RS485 negative terminal interface of the central control cabinet 200 through the same RS485 communication negative line B2.

[0052] In this embodiment, only a shared RS485 communication line is needed to replace the traditional six independent cables, reducing the number of input / output modules and the amount of construction work. Based on the characteristics of the RS485 communication line, it can maintain anti-interference performance during long-distance transmission, ensuring the stability of synchronous command issuance and status feedback among multiple frequency converter cabinets 100. Furthermore, when the communication link of the central control cabinet 200 is abnormal, each frequency converter cabinet 100 can still perform manual control through its local control panel, avoiding the risk of downtime due to communication interruption.

[0053] It is understood that the instructions generated by the central control cabinet 200 and the frequency converter 100 in this utility model application are all implemented using the existing central control cabinet 200 and frequency converter 100.

[0054] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the technical solution of this utility model, and are not intended to limit the specific implementation of this utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A frequency converter cabinet control device, characterized in that, The frequency converter cabinet includes a frequency converter and a mode switching switch, and the device includes: The first input terminal of the first intermediate relay is used to connect to the third phase voltage in the three-phase power supply, and the first output terminal of the first intermediate relay is connected to the first input terminal of the second intermediate relay. The first output terminal of the second intermediate relay is connected to the first digital input interface of the frequency converter, and the second output terminal of the second intermediate relay is connected to the neutral wire. The second output terminal of the first intermediate relay is connected to the second digital input interface of the frequency converter, and the third output terminal of the first intermediate relay is connected to the third digital input interface of the frequency converter. The second input terminal of the first intermediate relay and the second input terminal of the second intermediate relay are respectively connected to the first output voltage interface of the frequency converter; The input terminal of the mode switching switch is used to connect to the third phase voltage in the three-phase power supply, and the output terminal of the mode switching switch is connected to the neutral line. The first phase voltage input interface of the frequency converter is used to connect to the first phase voltage of the three-phase power supply, the second phase voltage input interface of the frequency converter is used to connect to the second phase voltage of the three-phase power supply, and the third phase voltage input interface of the frequency converter is used to connect to the third phase voltage of the three-phase power supply. The first phase voltage output interface, the second phase voltage output interface and the third phase voltage output interface in the frequency converter are respectively used to connect to the AC motor circuit; The positive RS485 interface of the frequency converter is connected to the positive RS485 communication line, which is used to connect to the positive RS485 interface of the central control cabinet. The negative RS485 interface of the frequency converter is connected to the negative RS485 communication line, which is used to connect to the negative RS485 interface of the central control cabinet. The positive and negative RS485 communication lines are also connected to the first analog ground interface.

2. The apparatus according to claim 1, characterized in that, The frequency converter cabinet also includes a control panel, which is connected to the frequency converter.

3. The apparatus according to claim 2, characterized in that, The control panel is equipped with a local frequency adjustment potentiometer; The second output voltage interface of the frequency converter is connected to the input terminal of the local frequency adjustment potentiometer. The first output terminal of the local frequency adjustment potentiometer is connected to the frequency input interface of the frequency converter. The second output terminal of the local frequency adjustment potentiometer is connected to the second analog ground interface of the frequency converter.

4. The apparatus according to claim 2, characterized in that, The control panel has a local start button; The fourth output terminal of the first intermediate relay is connected to the input terminal of the local start button, and the output terminal of the local start button is connected to the neutral wire.

5. The apparatus according to claim 2, characterized in that, The control panel is equipped with a local stop button; The fourth output terminal of the first intermediate relay is connected to the input terminal of the local stop button, and the output terminal of the local stop button is connected to the neutral wire.

6. The apparatus according to claim 2, characterized in that, The control panel is equipped with a local start button and a local stop button; The fourth output terminal of the first intermediate relay is connected to the input terminal of the local start button, and the output terminal of the local start button is connected to the input terminal of the local stop button. The output terminal of the local stop button is connected to the neutral wire.

7. The apparatus according to claim 2, characterized in that, The control panel is equipped with a running indicator light; The inverter's operating signal voltage input interface is used to connect to the third phase voltage of the three-phase power supply, the inverter's operating signal output interface is connected to the input terminal of the operating indicator light, and the neutral wire is connected to the output terminal of the operating indicator light.

8. The apparatus according to claim 2, characterized in that, The control panel is equipped with a fault indicator light; The fault signal voltage input interface of the frequency converter is used to connect to the third phase voltage of the three-phase power supply, the fault signal output interface of the frequency converter is connected to the input terminal of the fault indicator light, and the output terminal of the fault indicator light is connected to the neutral wire.

9. A frequency converter control system, characterized in that, The system includes a central control cabinet and a frequency converter control device according to any one of claims 1-8, wherein the RS485 communication positive line is connected to the RS485 positive terminal interface of the central control cabinet, and the RS485 communication negative line is connected to the RS485 negative terminal interface of the central control cabinet.

10. The system according to claim 9, characterized in that, The frequency converter cabinet control device includes several frequency converter cabinets. The RS485 positive terminals of the frequency converters in the several frequency converter cabinets are all connected to the RS485 positive terminal of the central control cabinet through the same RS485 communication positive line. The RS485 negative terminals of the corresponding frequency converters in the several frequency converter cabinets are all connected to the RS485 negative terminal of the central control cabinet through the same RS485 communication negative line.

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