Water-cooled frequency conversion cabinet for driving cutter head of shield machine

Abstract

The shield machine cutter driving water-cooling frequency conversion cabinet of the application comprises a cabinet body, a main power loop, six groups of frequency conversion driving units, a DP / Profinet communication network, a water-cooling monitoring system, a PLC control system and an auxiliary power system are arranged in the cabinet body; the main power loop adopts a 690VAC / 50Hz three-phase alternating current IT network power supply architecture, is powered by a twelve-pulse rectification mode, is distributed to the six groups of frequency conversion driving units through a circuit breaker busbar; each group of frequency conversion driving unit comprises a circuit breaker, an input reactor, a frequency converter and an output terminal connected in sequence; the frequency converter adopts a VaconNXP liquid-cooled frequency converter, each frequency converter is provided with an OPT-A1 basic I / O board, an OPT-A2 relay expansion board, an OPT-B8 expansion I / O board and an OPT-CP Profinet communication optional board; the DP / Profinet communication network comprises 16 industrial Ethernet switches, a touch screen man-machine interface, a PLC controller and the OPT-CP Profinet optional boards of the six frequency converters, and a real-time industrial Ethernet of a star topology is formed through a Profinet protocol.

Description

Technical Field

[0001] This invention relates to the field of power electronic equipment technology for tunnel construction, specifically to water-cooled frequency conversion control of shield machine cutterhead drive, and is particularly suitable for frequency conversion speed regulation and water-cooling heat dissipation control of multi-motor cutterhead drive systems for large-diameter tunnel boring machines. Specifically, it is a water-cooled frequency conversion control cabinet for shield machine cutterhead drive. Background Technology

[0002] As the core equipment for tunnel construction, tunnel boring machines (TBMs) require enormous torque and power output in their cutterhead drive systems. Modern large-diameter TBMs (over 10 meters in diameter) typically have a total cutterhead drive power ranging from 2000kW to 3600kW. To meet this ultra-high power output while ensuring redundant and reliable system operation, current mainstream cutterhead drive solutions mostly adopt a multi-motor synchronous drive architecture, meaning that 6 to 8 high-power asynchronous or permanent magnet synchronous motors jointly drive the cutterhead rotation.

[0003] For the variable frequency control requirements of multi-motor drives, existing technologies generally have the following problems: 1) The main power circuit design is complex and the electrical cabinets are bulky. In traditional solutions, each motor requires an independent frequency converter and supporting peripheral devices such as circuit breakers, reactors, and filters, resulting in a large number of electrical cabinets and a large footprint, making their arrangement extremely difficult within the narrow tunnel space of the tunnel boring machine. Taking the drive of six 350kW motors as an example, if a conventional independent frequency converter cabinet solution is used, at least six electrical cabinets are required, with a total width exceeding 6 meters. For the space of the supporting trolley at the rear of a tunnel boring machine with a diameter of 10 to 12 meters, the arrangement is extremely difficult.

[0004] 2) Centralized control and communication reliability issues. Multiple frequency converters need to exchange data at high speed with the host PLC to achieve precise synchronous control. Traditional analog control methods suffer from poor anti-interference capabilities, complex wiring, and low control accuracy. Although fieldbus technologies such as Profibus-DP and Profinet are widely used in industrial automation, in the special application scenario of high-power frequency converter drives for tunnel boring machines, how to achieve reliable network topology design and ensure real-time communication and electromagnetic interference resistance under the condition of multiple frequency converters operating in parallel remains a technical challenge.

[0005] 3) Limitations of heat dissipation methods. High-power frequency converters generate a large amount of heat during operation; the total heat generated by six 350kW-class frequency converters can reach tens of kilowatts. Traditional forced air cooling requires a large amount of cooling air. In the enclosed underground tunnel environment of a tunnel boring machine, ventilation conditions are limited, and the air duct design is complex and the fan noise is high. Although liquid cooling technology has been applied to some industrial frequency converter products, there is still a lack of mature engineering practice references for system-level water cooling pipeline design, leakage detection and protection, and water cooling status monitoring for integrating six high-power liquid-cooled frequency converters into a single-sided or multi-sided cabinet.

[0006] 4) Inadequate design of safety protection systems. The working environment of tunnel boring machines is harsh, with vibration, high temperature, high humidity, and dust posing severe challenges to the reliability of electrical equipment. Existing technologies lack systematic design for safety interlocking controls such as water cooling system leakage detection, condensate protection, emergency shutdown protection, and circuit breaker status feedback for frequency converter cabinets. In particular, the linkage protection mechanism between leakage detection and circuit breakers, as well as the reliable switching logic for remote / local dual-mode control, often suffer from design flaws in engineering practice, leading to malfunctions or protection failures.

[0007] 5) Redundancy and reliability of the control power supply system. The control circuits, PLC, communication equipment, sensors, etc. inside the frequency converter cabinet all rely on a 24V DC control power supply. During the continuous tunneling operation of the tunnel boring machine (TBM) for several months, a failure of the control power supply will lead to a complete shutdown. The redundancy design and fault self-diagnosis capabilities of the control power supply in existing solutions are generally insufficient.

[0008] Therefore, it is necessary to provide a water-cooled variable frequency control cabinet for the cutterhead drive of a tunnel boring machine to solve the above problems. Summary of the Invention

[0009] The purpose of this invention is to provide a water-cooled variable frequency control cabinet for tunnel boring machine cutterhead drive, which integrates six 350kW high-power liquid-cooled frequency converters into a compact cabinet, and features reliable DP / Profinet communication control, a complete water cooling and safety protection system, and highly integrated cutterhead drive variable frequency control.

[0010] The present invention achieves the above objectives through the following technical solutions: A water-cooled variable frequency control cabinet for tunnel boring machine cutterhead drive includes a cabinet, which houses a main power supply circuit, six sets of variable frequency drive units, a DP / Profinet communication network, a water-cooling monitoring system, a PLC control system, and an auxiliary power supply system. The main power supply circuit adopts a 690VAC / 50Hz three-phase AC IT network power supply architecture, and is distributed to six sets of frequency converter drive units through a twelve-pulse rectified power supply method and the circuit breaker busbar. Each variable frequency drive unit includes a circuit breaker, an input reactor, a frequency converter, and an output terminal connected in sequence; The frequency converters are Vacon NXP liquid-cooled frequency converters. Each frequency converter is equipped with an OPT-A1 basic I / O board, an OPT-A2 relay expansion board, an OPT-B8 expansion I / O board, and an OPT-CP Profinet communication option board. The DP / Profinet communication network includes a 16-port industrial Ethernet switch, a touch screen human-machine interface, a PLC controller, and OPT-CP Profinet option boards for six frequency converters, which form a star topology real-time industrial Ethernet network through the Profinet protocol. The water-cooling monitoring system includes a water-to-water heat exchanger and its water-cooling completion signal interface, 7-channel leak detectors, a water supply pump control circuit, a flow sensor interface, and a temperature sensor interface; the leak detector signal is isolated by a relay and then input to the inverter's digital input terminal and the PLC system's analog input module; The PLC control system uses a Siemens S7-1200 series CPU, and is equipped with digital input / output and analog input expansion modules. It receives signals such as manual / automatic reset, water cooling completion, condensation detection, emergency stop signal, circuit breaker status feedback, and water leakage alarm through hard-wired terminal blocks, and achieves real-time communication with the OPT-CP boards of six frequency converters through the Profinet network.

[0011] Furthermore, the electrical interlocking between the circuit breakers of the six sets of frequency converter drive units adopts a serial auxiliary contact link method. The normally open terminal of the auxiliary contact of the upper-level circuit breaker is connected to the auxiliary contact input terminal of the lower-level circuit breaker, forming a cascaded logic of step-by-step enabling. When any circuit breaker trips due to a fault, all downstream circuit breakers will not receive a closing enable signal, thus achieving local isolation of the fault.

[0012] Furthermore, in the DP / Profinet communication network, ports 1 to 6 of the switch are connected to the OPT-CPProfinet communication boards of six frequency converters, port 11 is connected to the PLC controller, and port 12 is connected to the touch screen human-machine interface; the switch is powered by a 24VDC redundant power supply, and the two power supplies are output in parallel through diode "OR" logic.

[0013] Furthermore, in the water-cooling monitoring system, the normally closed contacts of the 7-channel leakage detectors KL1 and LD1-LD6 are connected in series. When any one of them detects a leakage, the series circuit is disconnected. After the output of the leakage detector series circuit is connected in series with the water-cooling completion contact of the water-to-water heat exchanger, it is connected to the digital input terminal DI4 of the OPT-A1 board of the frequency converter through "AND" logic as the water-cooling OK interlock signal.

[0014] Furthermore, in the PLC control system, for the three redundant flow sensors on the same water-cooling circuit, the hardware circuit is designed with a "2 out of 3" voting logic - only when at least two of the three sensors have readings that are simultaneously lower than the flow threshold is it determined to be a flow insufficiency fault and triggers a protection shutdown.

[0015] Furthermore, the cabinet also includes an internal environmental control subsystem consisting of a redundant 24VDC switching power supply system, cabinet lighting circuit, cooling fan control circuit, heater control circuit, dehumidifier control circuit, temperature sensor JWT6011R, and heating resistor JRQ100.

[0016] Furthermore, the PLC's emergency stop processing logic is as follows: the normally closed contact of the emergency stop button opens → the coil of the emergency stop intermediate relay K6 is de-energized → all normally open contacts of K6 open → the DI1 start signal of the OPT-A1 board of all frequency converters is de-energized → the frequency converter enters the inertial stop mode; at the same time, after the PLC detects the emergency stop signal, it drives all circuit breaker shunt trip coils MX to open after a delay of about 200ms.

[0017] Furthermore, the signal from the condensation sensor-TT is simultaneously connected to the digital input terminal DIA of the inverter OPT-A1 board, the PLC analog input expansion module, and the cabinet heating and dehumidification control circuit; when the condensation sensor detects condensation, it automatically connects the power supply circuits of the heater and dehumidifier, and automatically stops after a 30-minute delay after the condensation is eliminated.

[0018] Furthermore, the OPT-B8 expansion I / O board of the frequency converter collects 4-20mA signals from the water-cooled outlet temperature sensor and flow sensor. When the outlet water temperature exceeds 55℃ or the flow rate is lower than the set threshold, the frequency converter issues a cooling fault alarm and automatically reduces the output power; if the fault lasts for more than 30 seconds, it triggers a protection shutdown.

[0019] Furthermore, the circuit breaker for the main power supply circuit is an NSX630H series 690V 630A 3P3D molded case circuit breaker, equipped with OF auxiliary contacts, SD trip indication contacts and MX shunt trip coil; the incoming line reactor and EMC filter are connected in series between the main incoming line terminal and the DC busbar.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1) Through the design of the 12-pulse rectified power supply busbar architecture and the circuit breaker cascade interlocking circuit, six 350kW high-power frequency converters and their peripheral devices are highly integrated into a compact cabinet, which greatly reduces the number of electrical cabinets and the floor space, making it particularly suitable for the application requirements of tunnel boring machines in narrow spaces. 2) The Profinet star network topology based on a 16-port industrial switch enables real-time synchronous communication between the PLC and 6 frequency converters in less than 2ms, providing communication assurance for precise torque distribution and speed synchronization of multi-motor cutter head drive; at the same time, the independent access design of the touch screen and PLC enables the network to have fault isolation capability and improves system maintainability. 3) The water-cooled safety interlock circuit based on the collaborative implementation of three I / O boards, OPT-A1 / A2 / B8, combines the triple protection logic of temperature, flow and leakage detection through the internal I / O of the frequency converter and the external logic of the PLC. This achieves a multi-level safety protection system from sensor acquisition → local judgment of the frequency converter → global judgment of the PLC → protection action, with fast response time and high reliability. 4) The "3-out-of-2" redundant sensor voting logic and integrated analog signal processing circuit design based on S7-1200 PLC effectively avoids protection malfunctions caused by single sensor failures while ensuring the monitoring accuracy of key parameters of the water cooling system, and significantly improves the operational reliability of the system in harsh construction environments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall electrical architecture of the cutterhead-driven water-cooled frequency converter cabinet.

[0022] Figure 2 for Figure 1 The detailed schematic diagram of the 12-pulse rectifier power supply circuit for the main power supply.

[0023] Figure 3 for Figure 1 Wiring diagram of the power circuit of a single variable frequency drive unit (taking VFD1 as an example).

[0024] Figure 4 This is a schematic diagram of the topology of a DP / Profinet communication network.

[0025] Figure 5 This is an interface connection diagram for the OPT-CPProfinet communication option board of the frequency converter.

[0026] Figure 6 This is the circuit diagram of a water-cooled monitoring system (including leakage detection and water-cooling completion signals).

[0027] Figure 7 Wiring diagram for digital / analog input / output of PLC control system. Detailed Implementation Example:

[0028] A water-cooled variable frequency control cabinet for tunnel boring machine cutterhead drive includes a cabinet, which houses a main power supply circuit, six sets of variable frequency drive units, a DP / Profinet communication network, a water-cooling monitoring system, a PLC control system, and an auxiliary power supply system. The main power supply circuit adopts a 690VAC / 50Hz three-phase AC IT network power supply architecture, and is distributed to six sets of frequency converter drive units through a twelve-pulse rectified power supply method and the circuit breaker busbar. Each variable frequency drive unit includes a circuit breaker, an input reactor, a frequency converter, and an output terminal connected in sequence; The frequency converters are Vacon NXP liquid-cooled frequency converters. Each frequency converter is equipped with an OPT-A1 basic I / O board, an OPT-A2 relay expansion board, an OPT-B8 expansion I / O board, and an OPT-CP Profinet communication option board. The DP / Profinet communication network includes a 16-port industrial Ethernet switch, a touch screen human-machine interface, a PLC controller, and OPT-CP Profinet option boards for six frequency converters, which form a star topology real-time industrial Ethernet network through the Profinet protocol. The water-cooling monitoring system includes a water-to-water heat exchanger and its water-cooling completion signal interface, 7-channel leak detectors, a water supply pump control circuit, a flow sensor interface, and a temperature sensor interface; the leak detector signal is isolated by a relay and then input to the inverter's digital input terminal and the PLC system's analog input module; The PLC control system uses a Siemens S7-1200 series CPU, and is equipped with digital input / output and analog input expansion modules. It receives signals such as manual / automatic reset, water cooling completion, condensation detection, emergency stop signal, circuit breaker status feedback, and water leakage alarm through hard-wired terminal blocks, and achieves real-time communication with the OPT-CP boards of six frequency converters through the Profinet network.

[0029] The electrical interlocking between the circuit breakers of the six sets of frequency converter drive units adopts a serial auxiliary contact link method. The normally open terminal of the auxiliary contact of the upper-level circuit breaker is connected to the auxiliary contact input terminal of the lower-level circuit breaker, forming a cascaded logic of step-by-step enabling. When any circuit breaker trips due to a fault, all downstream circuit breakers will not receive a closing enable signal, thus achieving local isolation of the fault.

[0030] In the DP / Profinet communication network, ports 1 to 6 of the switch are connected to the OPT-CPProfinet communication boards of six frequency converters, port 11 is connected to the PLC controller, and port 12 is connected to the touch screen human-machine interface. The switch is powered by a 24VDC redundant power supply, and the two power supplies are output in parallel through diode "OR" logic.

[0031] In the water-cooling monitoring system, the normally closed contacts of the 7-channel water leakage detectors KL1 and LD1-LD6 are connected in series. When any one of them detects a leak, the series circuit is disconnected. After the output of the water leakage detector series circuit is connected in series with the water-cooling completion contact of the water-to-water heat exchanger, it is connected to the digital input terminal DI4 of the OPT-A1 board of the frequency converter through "AND" logic as the water-cooling OK interlock signal.

[0032] In the PLC control system, for the three redundant flow sensors on the same water-cooling circuit, the hardware circuit is designed with a "2 out of 3" voting logic - only when at least two of the three sensors have readings that are simultaneously lower than the flow threshold is it determined to be a flow insufficiency fault and the protection shutdown is triggered.

[0033] The cabinet also includes an internal environmental control subsystem consisting of a redundant 24VDC switching power supply system, cabinet lighting circuit, cooling fan control circuit, heater control circuit, dehumidifier control circuit, temperature sensor JWT6011R, and heating resistor JRQ100.

[0034] The PLC's emergency stop processing logic is as follows: the normally closed contact of the emergency stop button opens → the coil of the emergency stop intermediate relay K6 is de-energized → all normally open contacts of K6 open → the DI1 start signal of the OPT-A1 board of all frequency converters is de-energized → the frequency converter enters the inertial stop mode; at the same time, after the PLC detects the emergency stop signal, it drives the shunt trip coil MX of all circuit breakers to open after a delay of about 200ms.

[0035] The signal from the condensation sensor-TT is simultaneously connected to the digital input terminal DIA of the inverter OPT-A1 board, the PLC analog input expansion module, and the cabinet heating and dehumidification control circuit. When the condensation sensor detects condensation, it automatically connects the power supply circuits of the heater and dehumidifier, and automatically stops after a 30-minute delay after the condensation is eliminated.

[0036] The OPT-B8 frequency converter's extended I / O board collects 4-20mA signals from the water-cooled outlet temperature sensor and flow sensor. The frequency converter internally issues a cooling fault alarm and automatically reduces output power when the outlet water temperature exceeds 55℃ or the flow rate is lower than the set threshold; if the fault lasts for more than 30 seconds, it triggers a protection shutdown.

[0037] The circuit breaker for the main power supply circuit is an NSX630H series 690V 630A 3P3D molded case circuit breaker, equipped with OF auxiliary contacts, SD trip indication contacts and MX shunt trip coil; the incoming line reactor and EMC filter are connected in series between the main incoming line terminal and the DC busbar. Application example:

[0038] This embodiment is applied to the cutterhead drive system of a large-diameter (12-meter diameter) tunnel boring machine, driving six 350kW three-phase asynchronous motors to rotate synchronously. The frequency converter cabinet integrates the main power supply circuit, six sets of frequency converter drive units, DP / Profinet communication network, water-cooled monitoring system, PLC control system and auxiliary power supply system into a single cabinet or dual-cabinet structure.

[0039] Overall electrical architecture such as Figure 1 As shown. An external 690VAC / 50Hz three-phase AC power supply is connected to the main power circuit via an IT network (ungrounded system). After 12-pulse rectification and filtering, the main power supply is distributed to six parallel variable frequency drive unit branches via DC busbars. Each branch is independently protected by circuit breakers QF1-QF6 (corresponding to -1Q1 to -6Q1), and fed into the corresponding Vacon NXP liquid-cooled frequency converters (VFD1 to VFD6) via input reactors L1-L6. The outputs of the six frequency converters are connected to six 350kW cutter head drive motors (+CUST-1M1 to +CUST-11M1) via terminal blocks XT7 to XT12.

[0040] All frequency converters' OPT-CPProfinet communication boards are connected to ports 1 to 6 of the 16-port switch-JH via RJ45 network cables. The PLC controller-A1 (S7-1200) is connected to port 11 of the switch, and the touch screen-TP1 is connected to port 12 of the switch. The switch is powered by a 24VDC power supply, and its grounding terminal is connected to the system common reference ground XD8.

[0041] The frequency converter cabinet adopts a dual-cabinet structure, consisting of a left cabinet and a right cabinet, which are bolted together to form a whole. The left cabinet (main control cabinet) mainly houses the PLC control system, touch screen human-machine interface, communication switch, control power system, and internal environmental control equipment. The right cabinet (power cabinet) mainly houses the main power input line, 6 sets of frequency converter drive units, circuit breaker busbars, water cooling pipe interfaces, and motor output terminal blocks. The two cabinets are connected to each other via busbar trunking and cable trays for power circuits and control signals.

[0042] The cabinet's external dimensions are: left cabinet width 800mm × depth 600mm × height 2200mm, right cabinet width 1600mm × depth 600mm × height 2200mm, total width 2400mm. Compared to the traditional 6-sided independent frequency converter cabinet solution (total width approximately 3600-4000mm), it saves approximately 40% of the floor space.

[0043] The cabinet has an IP54 protection rating (based on IEC60529 standard), meaning it is completely dustproof (IP5X) and splashproof (IPX4). EPDM (ethylene propylene diene monomer) sealing strips are installed around the cabinet doors, and multi-layer cable glands are used at cable inlets and outlets to ensure a tight seal.

[0044] It can form a 12-pulse rectified power supply architecture for the main power supply and an interlocking circuit for the circuit breaker. (See reference...) Figures 2-4 The main power supply circuit adopts a 690VAC / 50Hz three-phase AC IT network power supply. The IT network (an abbreviation of the French "IsoléTerre", meaning "ungrounded system") is a commonly used power supply method for mobile engineering machinery such as tunnel boring machines. Its characteristics are that the power supply neutral point is not directly grounded or is grounded through a high impedance. When a single-phase ground fault occurs, the leakage current is extremely small and will not trigger the protection trip. It can ensure that the system can continue to operate under the condition of a single-phase ground fault, which has extremely high engineering value for tunnel boring machine construction that has been continuously tunneling for several months.

[0045] The three-phase power supply lines L1 (yellow wire), L2 (green wire), and L3 (red wire) pass through the main incoming terminals in sequence: the incoming line reactor, the EMC filter (RFI filter), and the main contactor, finally reaching the DC busbar DC+ / DC-. The incoming line reactor suppresses high-order harmonic currents on the grid side, limiting the pollution of the grid by harmonics generated during the inverter's rectification process. Simultaneously, in the event of a short-circuit fault at the inverter's front end, the reactor limits the rate of rise of the short-circuit current, providing time for the circuit breaker to reliably disconnect. The EMC filter suppresses high-frequency common-mode and differential-mode electromagnetic interference generated by the inverter, ensuring the system meets the electromagnetic compatibility requirements of industrial environments.

[0046] The DC busbars DC+ and DC- are the common power supply trunk lines for the six variable frequency drive units. The six branches, which are led out from the DC busbars through fuse-type disconnect switches, pass through circuit breakers -1Q1 to -6Q1 and then enter their respective input reactors -L1 to -L6, and are then connected to the power input terminals L1 / L2 / L3 of the corresponding variable frequency drives VFD1 to VFD6.

[0047] Each NSX630H 690V 630A 3P3D circuit breaker is a high-performance molded case circuit breaker from Schneider Electric's CompactNSX series. Its rated operating voltage of 690VAC fully covers the operating voltage range of IT networks, and its rated current of 630A provides ample margin to handle full load (approximately 380A rated current) of a 350kW motor and starting inrush current. The circuit breaker is equipped with the following key accessories: OF auxiliary contact (open / closed position indicator contact): provides 1 normally open + 1 normally closed contact for feedback to the PLC on the actual opening and closing status of the circuit breaker. The normally open contacts 13 / 14 of the OF contact are closed when the circuit breaker is closed and open when it is open. SD Trip Indicator Contact (Fault Trip Alarm Contact): Provides 1 changeover contact. When the circuit breaker automatically trips due to overload, short circuit or leakage fault, the SD contact switches from normally closed to normally open and sends a fault alarm signal to the PLC. MX shunt trip coil: It receives a 24V control signal from the PLC digital output port. When the PLC issues a trip command, the MX coil is energized to drive the circuit breaker to trip immediately, realizing remote emergency shutdown. MN undervoltage trip coil (optional): When the control power supply voltage drops below 35%-70% of the rated value, the MN coil automatically triggers the circuit breaker to trip, preventing damage to the motor under undervoltage conditions.

[0048] The electrical interlocking between the six circuit breakers adopts a "serial auxiliary contact link" method. Its core design concept is to achieve "step-by-step enabling"—only when the upstream circuit breaker is in a normal closed state can the downstream circuit breaker have the closing condition, forming a cascaded interlocking. The specific implementation method is as follows: The auxiliary contacts 13 / 14 (OF normally open contacts) of each circuit breaker from -1Q1 to -6Q1 are connected in series to form a continuous electrical circuit. Contact 13 of -1Q1 is connected to the common signal line 19 (BN brown wire) on the XD8 terminal block, contact 14 of -1Q1 is connected to contact 13 of -2Q1, contact 14 of -2Q1 is connected to contact 13 of -3Q1, and so on, finally contact 14 of -6Q1 is connected to the digital input point I0.X of the PLC (or via an intermediate relay). This series link is also connected in parallel to the closing enable circuit of each circuit breaker itself.

[0049] The engineering significance of cascading interlocking is as follows: To prevent the inverter input side from experiencing an incomplete voltage waveform and thus damaging the rectifier module due to misoperation of the downstream circuit breaker when the upstream power circuit is not fully established; When a circuit breaker in the system trips due to a fault (e.g., -3Q1 trips due to overload), its OF contacts 13 / 14 open, causing downstream circuit breakers -4Q1, -5Q1, and -6Q1 to simultaneously lose their closing enable signals. However, upstream circuit breakers -1Q1 and -2Q1 are unaffected. This design limits the impact of the fault to downstream of the fault point, allowing normal upstream equipment to continue operating, thus achieving local fault isolation. All circuit breaker SD trip alarm contacts are connected to the PLC via separate wires. The PLC can accurately locate which circuit breaker has tripped due to a fault, and display specific fault information on the touch screen to guide maintenance personnel to quickly locate and troubleshoot the fault.

[0050] A 12-pulse rectified power supply method is adopted. The 12-pulse rectification is a low-harmonic rectification scheme achieved through two phase-shifting transformers and two sets of three-phase full-bridge rectifier circuits connected in parallel. The main features and harmonic reduction principle are detailed below: The harmonic reduction mechanism involves the mutual cancellation of characteristic harmonics. The characteristic harmonic orders injected into the power grid by a 6-pulse three-phase full-bridge rectifier circuit are h = 6k ± 1 (k is a positive integer), namely the 5th, 7th, 11th, 13th, 17th, 19th, 23rd, and 25th harmonics, etc. Among them, the 5th and 7th harmonics have the largest amplitudes, theoretically approximately 20% (1 / 5) and 14.3% (1 / 7) of the fundamental current, respectively. In this scheme, the two 6-pulse rectifier bridges are powered by phase-shifting transformer windings with a 30° phase difference on the secondary side. When the 5th and 7th harmonic currents generated by the two bridges are referred to the primary side of the transformer (power grid side), they cancel each other out due to the 30° phase shift, which results in a 180° electrical angle difference when superimposed on the power grid side. Similarly, the 17th and 19th harmonics also cancel each other out. After synthesis, the characteristic harmonic order injected into the power grid becomes h=12k±1, that is, only the 11th, 13th, 23rd and 25th harmonics remain. Moreover, the theoretical amplitude of each harmonic decreases with the increase of the order according to the law of 1 / h. The total amount of harmonic current injected into the power grid is significantly reduced from the mechanism. Harmonic current calculation comparison. The theoretical amplitude of the characteristic harmonic current of each order in an ideal 6-pulse rectifier is Ih=I1 / h: approximately 20% for the 5th order, approximately 14.3% for the 7th order, approximately 9.1% for the 11th order, and approximately 7.7% for the 13th order. The typical value of the total harmonic distortion (THDi) of the input current is approximately 30% to 35% (approximately 28% to 30% after configuring the input line reactor). In contrast, with 12-pulse rectification, the 5th, 7th, 17th, and 19th harmonics cancel each other out, and the lowest characteristic harmonic is the 11th order. The typical THDi value is reduced to 10% to 12%, and with the filtering effect of the CHK0650N6A0 input reactor in this scheme, it can be further reduced to 8% to 10%. Compared with the traditional 6-pulse scheme, the total harmonic current injected into the power grid by this scheme is reduced by about 60% to 70%; the 5th and 7th characteristic harmonics can theoretically be completely canceled. In actual engineering, considering factors such as the impedance difference between the two transformers and the imbalance of the two loads, the cancellation rate of the 5th and 7th harmonics can still reach more than 90%. Electrical parameters of the phase-shifting transformers. The two phase-shifting transformers adopt a three-winding structure with a Dy11d0 (or Dy1d11) connection group: the primary winding is delta (D) connected to a 690VAC power grid; the two secondary windings are star and delta connected respectively, with the output voltage phases differing by 30° electrical degrees. The transformer capacity is selected to match 1.05 to 1.1 times the total input capacity of the connected frequency converter drive unit, ensuring balanced distribution of the two secondary winding capacities; the short-circuit impedance is designed at 6% to 8%, and the impedances of the two secondary windings are kept consistent (deviation not exceeding 5%) to ensure equal current operation of the two rectifier bridges and achieve optimal harmonic cancellation.

[0051] The DC bus voltage ripple frequency of the 12-pulse rectification is 600Hz (50Hz×12), and the ripple amplitude is approximately 1% of the theoretical DC voltage. This is significantly better than the 300Hz ripple frequency and approximately 4.2% ripple amplitude of the 6-pulse rectification, which reduces the ripple current stress on the DC bus capacitor, extends capacitor life, and improves the output waveform quality of the inverter's IGBT bridge. The typical input-side displacement power factor is improved to over 0.97, meeting the power factor requirements of industrial applications without additional active front-end (AFE), thus achieving cost-effectiveness. After 12-pulse rectification, THDi is reduced to below 10%. With just the input reactor, the above standard limit requirements can be met at the common connection point of the shield tunnel construction power supply system. There is no need to add a large-capacity harmonic filter cabinet, saving cabinet space and reducing system losses.

[0052] In the main power supply circuit, the coordination of protection devices follows the cascading protection principles of the "IEC 60947-2 Low-voltage switchgear and controlgear - Circuit breakers" and "IEC 60269 Low-voltage fuses" standards. Specifically: (1) The fuse-type disconnector at the main incoming line provides upstream backup for short circuit protection. Its fuse rated current is selected as 800A (gG type), and the fuse characteristic is "full range breaking", that is, all overcurrent values ​​from the minimum melting current to the rated short circuit breaking capacity can be reliably broken.

[0053] (2) The instantaneous trip setting (Ii) of each branch circuit breaker -1Q1 to -6Q1 is set to 8 times the rated current (i.e., 8×630A=5040A), and the short-delay trip setting (Isd) is set to 5 times the rated current (i.e., 5×630A=3150A), with a delay time of 0.1 seconds (corresponding to SORT=OFF position). This setting method makes the instantaneous trip mainly used for rapid disconnection when a metallic short circuit occurs at the input terminal of the frequency converter (disconnection time is less than 10ms), while the short-delay trip is used for overcurrent protection when a breakdown fault occurs in the input rectifier bridge of the frequency converter (disconnection time is about 0.1 seconds), providing a protection coordination time window for the semiconductor fuse inside the downstream frequency converter.

[0054] (3) The built-in semiconductor fast fuse (aR type, dedicated to semiconductor protection) is located between the DC bus and the IGBT inverter bridge. Its I²t Joule integral value is much smaller than that of the circuit breaker. When the IGBT has a short circuit fault, the fast fuse melts within 1-2ms to protect the IGBT module from damage. The circuit breaker, due to its stronger I²t tolerance, will not operate in such faults, thus realizing the hierarchical protection strategy of "fast fuse protects power devices, circuit breaker protects lines and upstream equipment".

[0055] To form a dual-redundant DP communication network topology based on Profinet, see [link / reference]. Figure 5 , 6 The DP / Profinet communication network uses a 16-port industrial Ethernet switch -JH as its core, constructing a star topology Profinet real-time industrial Ethernet. Profinet is an open automation bus standard based on industrial Ethernet, launched by Profibus & Profinet International (PI) organization. It is fully compatible with the IEEE 802.3 Ethernet standard, supports standard IT protocols such as TCP / IP and UDP / IP, and adds ProfinetRT (Real-Time) and IRT (Isochronous Real-Time) mechanisms to meet the deterministic communication requirements of motion control and high-speed I / O.

[0056] The switch-JH uses a PhoenixContact or equivalent 16-port unmanaged industrial Ethernet switch, supporting 10 / 100Mbps auto-sensing speed and full-duplex communication mode. The switch is powered by 24VDC, with its power supply terminals (+24V and 0V) connected to the 24V control power bus and 0V common bus on the XD8 terminal block.

[0057] Data exchange between the PLC and each frequency converter adopts the ProfinetRT communication protocol. The data frame structure follows the IEEE 802.1Q VLAN tag frame format, and the priority field (PCP) is set to 6 (highest priority) to ensure that real-time control data is not dropped when the network is congested.

[0058] Based on 6 frequency converters × 14 bytes of input data + 14 bytes of output data, the PLC needs to process a total of 168 bytes of real-time data in each communication cycle. With a 100Mbps Ethernet bandwidth, the transmission time per byte is approximately 0.08μs (microseconds), so the theoretical transmission time for 168 bytes is only about 13.4μs. Considering the Ethernet frame overhead (8 bytes preamble + 12 bytes inter-frame interval + 14 bytes MAC header + 20 bytes IP header + 8 bytes UDP header + 4 bytes CRC checksum), switch forwarding delay (typically 5-10μs / frame), and PLC program scan cycle (typically 1-5ms), the overall system communication refresh cycle can be controlled within 2ms, fully meeting the real-time requirements of synchronous control of multiple motors in the cutter head drive.

[0059] The communication network implements a dual redundancy design at both the power supply and physical connection levels: (1) Control power redundancy: The 24V power supply of the switch-JH comes from the dual-redundant switching power supply module-U7 (model DRP-240-24, output 24VDC / 10A) in the cabinet. The AC input terminals of the switching power supply are respectively led out from two independent control transformers (220V tap of TA3 and auxiliary transformer), and the output is connected in parallel using diode "OR" logic. When one power supply fails, the other automatically and seamlessly takes over, which will not cause the switch to power out and restart instantly. In addition, an electronic miniature circuit breaker is connected in series in the power supply circuit of the switch for short circuit protection.

[0060] (2) Physical connection redundancy: Although each node uses a single RJ45 network cable (Cat5e STP shielded twisted pair) to the switch, the key nodes in the wiring system (PLC, touch screen, switch) share a common reference ground connected to the 24V / 0V power bus on the XD8 terminal block. All RJ45 network cables use STP (Shielded Twisted Pair) shielded twisted pair, and the shielding layer is grounded at one end at the switch (through the metal shell of the RJ45 plug contacting the metal casing of the switch), effectively preventing high-frequency electromagnetic interference generated by the frequency converter from coupling into the communication system through the network cable.

[0061] The space behind the tunnel boring machine contains numerous sources of strong electromagnetic interference, such as frequency converters, high-power motors, and transformers. This communication network incorporates anti-interference design features in the following aspects: (1) Separate routing of signal lines and power lines: All RJ45 communication network cables shall be laid in the cabinet along independent metal cable trays, maintaining a distance of at least 200mm from 690VAC power cables and motor output cables, and avoiding parallel routing. When crossing is unavoidable, a 90° orthogonal crossing shall be used.

[0062] (2) Shielding treatment: The shielding layer of each RJ45 network cable is grounded at one end through the RJ45 metal shell at the switch end. The shielding layer of the network cable at the inverter end is not grounded (the RJ45 socket on the OPT-CP board has a plastic shell and is not grounded), which avoids the shielding layer circulating current interference caused by ground potential difference.

[0063] (3) A common mode choke and decoupling capacitor (100nF ceramic capacitor + 47μF aluminum electrolytic capacitor in parallel) are installed in the 24V power supply circuit of the switch to effectively suppress the high-frequency common mode interference signal coupled in through the 24V power line.

[0064] (4) The 24V power supply (powered by the onboard DC / DC converter) of the OPT-CP communication board of all frequency converters is isolated from the 24V power supply of the switch through different switching power supply branches. The power supply of the communication board at the frequency converter end is provided by the switching power supply taken from the DC bus inside the frequency converter, and the power supply of the switch is provided by the independent 24V switching power supply in the cabinet. The two are electrically isolated through the Ethernet Transformer (integrated inside the RJ45 socket), with an isolation withstand voltage of 1500VAC, which completely cuts off the common ground interference loop formed through the 24V power line.

[0065] The pure Profinet network is adopted, but considering that there may be a host computer monitoring system or other subsystems using the Profibus-DP protocol at the tunnel boring machine construction site, the OPT-CP communication board supports both Profinet and Profibus-DP protocols. The communication protocol can be switched through the inverter parameter settings (Parameter Group 5.x).

[0066] In applications requiring interface with the Profibus-DP system, the D-sub 9-pin connector (DB9 female) on the OPT-CP board can be directly connected to the Profibus-DP bus cable (purple 2-core shielded twisted pair, characteristic impedance 150Ω). The terminating resistor is activated via a DIP switch on the OPT-CP board. In this case, the Profinet RJ45 interface and the DB9 interface cannot be used simultaneously; they are mutually exclusive.

[0067] It is worth noting that the communication cycle of ProfinetRT (1-2ms level) is far superior to that of Profibus-DP (typical value 10-50ms level, depending on bus speed and number of stations). Therefore, this system prioritizes Profinet to ensure the real-time response capability required for the synchronous control of multiple motors of the cutter head.

[0068] A water-cooled safety interlock circuit based on the OPT-A1 / A2 / B8 multi-layer I / O board is established: Each Vacon NXP liquid-cooled inverter control unit is equipped with three I / O expansion boards, building a complete hardware platform for signal acquisition, logic judgment, and output control. Refer to [link to relevant documentation] for the functional division and port allocation of the three boards. Figure 7 ; The water-cooled safety interlock circuit is the core protection mechanism that ensures the safe operation of the frequency converter under sufficient cooling conditions. Its logic design is divided into three levels: First layer: Sensor layer (physical signal acquisition)

[0069] The sensor network of the water-cooling system includes: (1) 7-channel water leakage detectors: KL1 (main water leakage detector, installed in the water collection tank at the bottom of the cabinet) and LD1-LD6 (installed below the water cooling plate of each frequency converter and at the key joint of the water cooling pipeline respectively). Each water leakage detector contains a pair of electrodes and a signal processing circuit. When water leakage is detected, the conductivity between the electrodes increases and the normally closed contact of the detector output opens.

[0070] The normally closed contacts of the 7-channel water leakage detector are connected in series. Specifically, one end of the KL1 contact is connected to the positive terminal of the 24VDC power supply (via fuse-F4), and the other end is connected in series with the normally closed contacts of LD1→LD2→LD3→LD4→LD5→LD6→LD7. The output of the last contact, LD7, serves as the "leakage OK" signal. In other words, when any of the 7 detectors detects a leak, the normally closed contacts in the entire series circuit open, causing the "leakage OK" signal to change from high level (24V) to low level (0V).

[0071] (2) Water cooling completion signal: from the control box of the water-to-water heat exchanger. When the water pump of the water-to-water heat exchanger starts successfully, the coolant circulates normally and the outlet water temperature is stable within the set range, the water cooling completion contact -KS closes and outputs a 24V high-level signal.

[0072] (3) Flow sensor: A turbine flow meter (or electromagnetic flow meter) installed on the water-cooled main pipeline outputs a 4-20mA analog signal to the analog input channel of the OPT-B8 board. The normal flow range corresponds to 12-20mA. If the flow is below 12mA (corresponding to a flow rate less than 50% of the set value), it is determined that the flow is insufficient.

[0073] (4) Temperature sensors: including water-cooled outlet water temperature sensor (PT100 thermal resistance, converted into a 4-20mA signal by a transmitter and connected to the OPT-B8 board), cabinet condensing temperature sensor (-TT), and inverter built-in radiator temperature sensor (read through the inverter's internal circuit). Second layer: Inverter local judgment layer

[0074] The "Leakage OK" signal and the water cooling completion signal are combined via an AND logic (either in series or through a relay logic combination) to form the "Water Cooling OK" signal, which is then connected to the digital input terminal DI4 (terminal 8) of the inverter's OPT-A1 board. The inverter's internal parameter settings configure this DI4 for "external interlock" function. When the DI4 input is low, the inverter refuses to start (even if a Profinet start command is received) and generates an "ExternalFault" fault alarm.

[0075] Meanwhile, the OPT-B8 board collects the water cooling outlet temperature and the 4-20mA signal from the flow sensor, which is then used to make judgments within the inverter: when the outlet water temperature exceeds 55℃ or the flow rate is lower than the set threshold, the inverter issues a "CoolingFault" alarm and limits the output power (automatic derating operation). If the fault lasts for more than 30 seconds, the inverter will be triggered to shut down for protection. Third layer: PLC global decision layer (voting logic)

[0076] The PLC acquires data from various sensors in the water cooling system through the following methods: (1) Read the temperature and flow data collected by the OPT-B8 board of each frequency converter through Profinet periodic communication. (2) Read the "Water Cooling OK" signal (a relay-converted signal from DI4) through the digital input module. (3) Read the 4-20mA signal of the 3 redundant flow sensors directly through the analog input module.

[0077] The key protection logic implemented in the hardware circuit is as follows: "3-out-of-2" flow redundancy voting logic: For a water-cooled circuit employing three redundant flow sensors, the PLC sequentially reads the values ​​from the three sensors (Q1, Q2, Q3) in each scan cycle and compares them with the set low flow threshold QL. Let three Boolean variables F1, F2, and F3 represent whether the three sensors detect insufficient flow: - If Q1 <QL then F1 =TRUE else F1 = FALSE - If Q2<QL then F2 = TRUE else F2 = FALSE - If Q3 <QL then F3 = TRUE else F3 = FALSE The voting output is: FLOW_FAULT = (F1 AND F2) OR (F2 AND F3) OR (F1 AND F3) That is, a true flow fault is determined only when at least two of the three sensors simultaneously indicate insufficient flow. If only one sensor indicates insufficient flow (e.g., F1=TRUE, F2=FALSE, F3=FALSE), the PLC determines it as a sensor fault rather than a flow fault, and only generates a "sensor fault warning" on the touch screen instead of triggering a shutdown protection.

[0078] This "2 out of 3" voting logic is based on the "K out of N" redundancy theory in reliability engineering. It can reduce the probability of the system failing due to random sensor failures from the single sensor failure rate λ to approximately 3λ² (i.e., from 10⁻⁻⁶). 4 / h magnitude reduced to 10⁻ 8 (on the order of / h), significantly improving the reliability of the water-cooled protection system.

[0079] Protection Action Sequence: When the PLC determines that a real flow fault has occurred, the following protection action sequence is executed: 1. T=0ms: The system sends a "fast stop" command (Control Word bit 0=0, bit1=1, corresponding to "CoastStop" inertial stop mode) to 6 frequency converters via Profinet. All frequency converters immediately block the IGBT drive pulses, and the motors coast to a stop. 2. T=100ms: The PLC drives the circuit breaker shunt trip coil MX through the digital output port, causing all 6 circuit breakers to trip simultaneously, cutting off the input power to the frequency converters. 3. T=500ms: The PLC sends fault alarm information to the touch screen and water exchanger, recording the time of fault occurrence, fault type, and sensor readings to the internal fault history buffer. 4. After the fault is cleared, the PLC fault lockout state must be manually reset via the reset button S8 before the system can be restarted.

[0080] Compared with the prior art, the present invention has the following beneficial effects: 1) Through the design of the 12-pulse rectified power supply busbar architecture and the circuit breaker cascade interlocking circuit, six 350kW high-power frequency converters and their peripheral devices are highly integrated into a compact cabinet, which greatly reduces the number of electrical cabinets and the floor space, making it particularly suitable for the application requirements of tunnel boring machines in narrow spaces. 2) The Profinet star network topology based on a 16-port industrial switch enables real-time synchronous communication between the PLC and 6 frequency converters in less than 2ms, providing communication assurance for precise torque distribution and speed synchronization of multi-motor cutter head drive; at the same time, the independent access design of the touch screen and PLC enables the network to have fault isolation capability and improves system maintainability. 3) The water-cooled safety interlock circuit based on the collaborative implementation of three I / O boards, OPT-A1 / A2 / B8, combines the triple protection logic of temperature, flow and leakage detection through the internal I / O of the frequency converter and the external logic of the PLC. This achieves a multi-level safety protection system from sensor acquisition → local judgment of the frequency converter → global judgment of the PLC → protection action, with fast response time and high reliability. 4) The "3-out-of-2" redundant sensor voting logic and integrated analog signal processing circuit design based on S7-1200 PLC effectively avoids protection malfunctions caused by single sensor failures while ensuring the monitoring accuracy of key parameters of the water cooling system, and significantly improves the operational reliability of the system in harsh construction environments.

[0081] The above are merely some embodiments of the present invention. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of the present invention, and all such modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A water-cooled frequency converter cabinet for driving the cutterhead of a tunnel boring machine, characterized in that: The cabinet includes a main power supply circuit, six sets of frequency converter drive units, a DP / Profinet communication network, a water-cooling monitoring system, a PLC control system, and an auxiliary power supply system. The main power supply circuit adopts a 690VAC / 50Hz three-phase AC IT network power supply architecture, and is distributed to six sets of frequency converter drive units through a twelve-pulse rectified power supply method and circuit breaker busbars; Each variable frequency drive unit includes a circuit breaker, an input reactor, a frequency converter, and an output terminal connected in sequence; The frequency converters are Vacon NXP liquid-cooled frequency converters. Each frequency converter is equipped with an OPT-A1 basic I / O board, an OPT-A2 relay expansion board, an OPT-B8 expansion I / O board, and an OPT-CP Profinet communication option board. The DP / Profinet communication network includes a 16-port industrial Ethernet switch, a touch screen human-machine interface, a PLC controller, and OPT-CP Profinet option boards for six frequency converters, which form a star topology real-time industrial Ethernet network through the Profinet protocol. The water-cooling monitoring system includes a water-to-water heat exchanger and its water-cooling completion signal interface, 7-channel leak detectors, a water supply pump control circuit, a flow sensor interface, and a temperature sensor interface; the leak detector signal is isolated by a relay and then input to the inverter's digital input terminal and the PLC system's analog input module; The PLC control system uses a Siemens S7-1200 series CPU, and is equipped with digital input / output and analog input expansion modules. It receives signals such as manual / automatic reset, water cooling completion, condensation detection, emergency stop signal, circuit breaker status feedback, and water leakage alarm through hard-wired terminal blocks, and achieves real-time communication with the OPT-CP boards of six frequency converters through the Profinet network.

2. The shield machine cutterhead drive water-cooled frequency converter cabinet according to claim 1, characterized in that: The electrical interlocking between the circuit breakers of the six sets of frequency converter drive units adopts a serial auxiliary contact link method. The normally open terminal of the auxiliary contact of the upper-level circuit breaker is connected to the auxiliary contact input terminal of the lower-level circuit breaker, forming a cascaded logic of step-by-step enabling. When any circuit breaker trips due to a fault, all downstream circuit breakers will not receive a closing enable signal, thus achieving local isolation of the fault.

3. The shield machine cutterhead drive water-cooled frequency converter cabinet according to claim 2, characterized in that: In the DP / Profinet communication network, ports 1 to 6 of the switch are connected to the OPT-CPProfinet communication boards of six frequency converters, port 11 is connected to the PLC controller, and port 12 is connected to the touch screen human-machine interface. The switch is powered by a 24VDC redundant power supply, and the two power supplies are output in parallel through diode "OR" logic.

4. The water-cooled frequency converter cabinet for driving the cutterhead of a tunnel boring machine according to claim 3, characterized in that: In the water-cooling monitoring system, the normally closed contacts of the 7-channel water leakage detectors KL1 and LD1-LD6 are connected in series. When any one of them detects a leak, the series circuit is disconnected. After the output of the water leakage detector series circuit is connected in series with the water-cooling completion contact of the water-to-water heat exchanger, it is connected to the digital input terminal DI4 of the OPT-A1 board of the frequency converter through "AND" logic as the water-cooling OK interlock signal.

5. A water-cooled frequency converter cabinet for driving the cutterhead of a tunnel boring machine according to claim 4, characterized in that: In the PLC control system, for the three redundant flow sensors on the same water-cooling circuit, the hardware circuit is designed with a "2 out of 3" voting logic; only when at least two of the three sensors read below the flow threshold at the same time is it determined to be a flow insufficiency fault and triggers protection shutdown.

6. A water-cooled frequency converter control cabinet for shield machine cutterhead drive according to claim 5, characterized in that: The cabinet also includes an internal environmental control subsystem consisting of a redundant 24VDC switching power supply system, cabinet lighting circuit, cooling fan control circuit, heater control circuit, dehumidifier control circuit, temperature sensor JWT6011R, and heating resistor JRQ100.

7. A water-cooled variable frequency control cabinet for shield machine cutterhead drive according to claim 6, characterized in that: The PLC's emergency stop processing logic is as follows: the normally closed contact of the emergency stop button opens → the coil of the emergency stop intermediate relay K6 is de-energized → all normally open contacts of K6 open → the DI1 start signal of the OPT-A1 board of all frequency converters is de-energized → the frequency converter enters the inertial stop mode; at the same time, after the PLC detects the emergency stop signal, it drives the shunt trip coil MX of all circuit breakers to open after a delay of about 200ms.

8. A water-cooled variable frequency control cabinet for shield machine cutterhead drive according to claim 7, characterized in that: The signal from the condensation sensor-TT is simultaneously connected to the digital input terminal DIA of the inverter OPT-A1 board, the PLC analog input expansion module, and the cabinet heating and dehumidification control circuit. When the condensation sensor detects condensation, it automatically connects the power supply circuits of the heater and dehumidifier, and automatically stops after a 30-minute delay after the condensation is eliminated.

9. A water-cooled variable frequency control cabinet for shield machine cutterhead drive according to claim 8, characterized in that: The OPT-B8 frequency converter's extended I / O board collects 4-20mA signals from the water-cooled outlet temperature sensor and flow sensor. The frequency converter internally issues a cooling fault alarm and automatically reduces output power when the outlet water temperature exceeds 55℃ or the flow rate is lower than the set threshold; if the fault lasts for more than 30 seconds, it triggers a protection shutdown.

10. A water-cooled variable frequency control cabinet for shield machine cutterhead drive according to claim 9, characterized in that: The circuit breaker for the main power supply circuit is an NSX630H series 690V 630A 3P3D molded case circuit breaker, equipped with OF auxiliary contacts, SD trip indication contacts and MX shunt trip coil; the incoming line reactor and EMC filter are connected in series between the main incoming line terminal and the DC busbar.

Images