A flameproof high voltage inverter for mining

Abstract

The invention discloses a mine flameproof high-voltage frequency converter, comprising a flameproof housing, a phase-shifting transformer, a conversion circuit, a control unit and a cooling system. The conversion circuit comprises a plurality of series-connected power units, the AC input end of the power unit is connected to the three-phase output end of the low-voltage side of the phase-shifting transformer through a cable, the flameproof housing comprises a transformer cavity, a power unit cavity and a control and cooling cavity in sequence along the longitudinal direction, the phase-shifting transformer, the conversion circuit and the control unit are respectively arranged in the corresponding transformer cavity, the power unit cavity and the control cavity; the partition between the transformer cavity and the power unit cavity comprises a cable through hole, the cable passes through the cable through hole to connect the phase-shifting transformer and the power unit; the control unit and some components of the cooling system are arranged in the control and cooling cavity. The mine flameproof high-voltage frequency converter of the invention has a small volume and a high power density.

Description

[Technical field]

[0001] The invention relates to a high-voltage frequency converter, in particular to a flameproof high-voltage frequency converter for mining. [Background Technology]

[0002] With the advancement of technology, the production capacity of modern mines has been continuously expanded. The voltage of the motor for the underground main conveyor belt has been increased to 10kV, and the motor power has been continuously increased. The original method of direct motor starting can no longer meet the production needs. The use of 10kV input / 0-10kV output mine explosion-proof and intrinsically safe high-voltage inverter drive has become a good solution. The traditional 10kV input / 0-10kV output mine explosion-proof and intrinsically safe high-voltage inverter generally has low integration and poor reliability.

[0003] The invention with application number CN201110271028.5 discloses a flameproof high-voltage inverter for mining, including a flameproof box for a phase-shifting transformer unit and a flameproof box for a power unit. A phase-shifting isolation transformer and a heat dissipation system are arranged in the flameproof box for the phase-shifting transformer unit, and a plurality of groups of power units connected in series, a control unit and a heat dissipation system are arranged in the flameproof box for the power unit. The high-voltage side of the phase-shifting isolation transformer is connected in series in a three-phase high-voltage power grid, and the plurality of groups of power units connected in series are respectively connected to the low-voltage side of the phase-shifting isolation transformer, and the power unit and the control unit are connected via optical fiber.

[0004] The phase-shifting transformer and the frequency converter of the invention are both independent flameproof units, which are connected by multiple flameproof cables for mining. This results in the limited space in the coal mine, and the flameproof cables for mining in this solution are long, bulky, low in power density, and poor in reliability. [Summary of the invention]

[0005] The technical problem to be solved by the present invention is to provide a mining flameproof high-voltage frequency converter with small volume and high power density.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is a mining explosion-proof high-voltage inverter, including an explosion-proof shell, a phase-shifting transformer, a conversion circuit, a control unit and a cooling system. The conversion circuit includes multiple groups of power units connected in series, and the AC input end of the power unit is connected to the three-phase output end of the low-voltage side of the phase-shifting transformer through a cable. The explosion-proof shell includes a transformer cavity, a power unit cavity and a control and cooling cavity in the longitudinal direction. The phase-shifting transformer, the conversion circuit and the control unit are respectively arranged in the corresponding transformer cavity, the power unit cavity and the control cavity; the partition between the transformer cavity and the power unit cavity includes a cable through-hole, and the cable passes through the cable through-hole to connect the phase-shifting transformer and the power unit; the control unit and some components of the cooling system are arranged in the control and cooling cavity.

[0007] The above-mentioned mining flameproof high-voltage inverter has a cooling system comprising an internal water circulation system, an external water circulation system and a transformer cooling device. The transformer cooling device is installed in the transformer cavity, and the water circuit of the transformer cooling device is connected in series to the water circuit of the external water circulation system.

[0008] The above-mentioned mining flameproof high-voltage inverter, the transformer cooling device includes a fan and a hot air water-cooled radiator, the phase-shifting transformer, the fan and the hot air water-cooled radiator are arranged in the air duct inside the transformer cavity, and the water channel of the hot air water-cooled radiator is connected in series to the water channel of the external water circulation system.

[0009] In the above-mentioned mining explosion-proof high-voltage inverter, the internal water circulation system and the external water circulation system exchange heat through a water-water plate heat exchanger, and the external water circulation system includes an inlet flange interface and an outlet flange interface; the inlet flange interface and the outlet flange interface are arranged on the side wall of the explosion-proof shell; the inlet flange interface is connected to the external circulation water inlet of the water-water plate heat exchanger, the external circulation water outlet of the water-water plate heat exchanger is connected to the water inlet of the hot air water-cooling radiator, and the water outlet of the hot air water-cooling radiator is connected to the outlet flange interface; the internal water circulation system includes an internal circulation water pump and an inverter water-cooling radiator, the internal circulation water outlet of the water-water plate heat exchanger is connected to the inlet of the internal circulation water pump, and the outlet of the internal circulation water pump is connected to the internal circulation water inlet of the water-water plate heat exchanger through the water channel of the inverter water-cooling radiator; the cooling water circulated in the internal water circulation system is deionized water.

[0010] The above-mentioned mining flameproof high-voltage inverter, the power unit includes a radiator for cooling power components, the radiators of the power unit are connected in parallel to form the inverter water-cooling radiator; the water-water plate heat exchanger and the internal circulation water pump are arranged in the control and cooling cavity.

[0011] In the above-mentioned explosion-proof high-voltage inverter for mining, the output ends of multiple groups of power units connected in series are connected to two groups of output terminals of the high-voltage inverter through two groups of contactor contacts, and the two groups of contactor contacts are connected in parallel; the cable is a three-core non-explosion-proof cable, and each cable contains 3 core wires.

[0012] The above-mentioned mining explosion-proof high-voltage inverter has a six-phase input at the AC input end of the power unit and a single-phase output; the power unit includes two unit circuits, and the unit circuit includes a three-phase full-bridge rectifier circuit, a DC bus, a full-bridge inverter circuit and a control board. The output end of the three-phase full-bridge rectifier circuit is connected to the input end of the full-bridge inverter circuit through the DC bus, and the output end of the full-bridge inverter circuit is the AC output end of the unit circuit; the four drive signal input ends of the full-bridge inverter circuit are respectively connected to the drive signal output end of the control board; the AC output ends of the two unit circuits are connected in series as the AC output end of the power unit; the AC input end of the three-phase full-bridge rectifier circuit of the first unit circuit is connected to the first three-phase AC power supply, and the AC input end of the three-phase full-bridge rectifier circuit of the second unit circuit is connected to the second three-phase AC power supply.

[0013] In the above-mentioned explosion-proof high-voltage inverter for mining, the midpoint of the first half bridge of the full-bridge inverter circuit of the first unit circuit is connected to the first terminal of the AC output end of the power unit, and the midpoint of the first half bridge of the full-bridge inverter circuit of the second unit circuit is connected to the second terminal of the AC output end of the power unit; the midpoint of the second half bridge of the full-bridge inverter circuit of the first unit circuit is connected to the midpoint of the second half bridge of the full-bridge inverter circuit of the second unit circuit.

[0014] In the above-mentioned explosion-proof high-voltage inverter for mining, the power unit includes a heat sink for power components, and the heat sink is shared by two unit circuits; the midpoint of the second half bridge of the full-bridge inverter circuit of the first unit circuit is connected to the heat sink through a grounding resistor.

[0015] The above-mentioned explosion-proof high-voltage inverter for mining adjusts the output voltage of the power unit by adjusting the phase difference and output frequency of the AC outputs of the two unit circuits.

[0016] The mining flameproof high-voltage frequency converter of the present invention has small volume and high power density. [Drawings]

[0017] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0018] Figure 1 The invention discloses a circuit diagram of a main circuit of a flameproof high-voltage frequency converter for mining use according to an embodiment of the present invention.

[0019] Figure 2 It is a diagram of the internal structure layout of a flameproof high-voltage frequency converter for mining use according to an embodiment of the present invention.

[0020] Figure 3 It is a cooling water system diagram of a mining flameproof high-voltage inverter according to an embodiment of the present invention.

[0021] Figure 4 It is an electrical schematic diagram of the main circuit of the power unit according to an embodiment of the present invention.

[0022] Figure 5 It is a principle block diagram of a power unit control circuit according to an embodiment of the present invention. [Specific implementation method]

[0023] The structure of the high power density mining flameproof and intrinsically safe high voltage inverter with built-in phase-shifting rectifier transformer in the embodiment of the present invention is as follows: Figures 1 to 3As shown in the figure, the rated output voltage of this type of inverter can reach up to 10kV. The rated input voltage of this inverter is 10kV. This type of inverter integrates 1 rectifier phase-shifting transformer, 12 power units, 1 control unit, 1 water cooling unit and 24 three-core non-explosion-proof cables in the cavity of the flameproof shell. The cable connecting the rectifier phase-shifting transformer and the power unit directly adopts non-explosion-proof cable, which makes the connection more convenient, fast, safe and reliable, and at the same time reduces the size of the entire inverter and reduces the cost.

[0024] like Figure 1 As shown, XP1 is the inverter input cable connector, which uses a mine flameproof high-voltage connector plug, XS1 is the inverter input cable socket, which uses a mine flameproof high-voltage connector socket, T is a rectifier phase-shifting transformer, A1-A4, B1-B4, C1-C4 are three groups of serially connected power units, KM1 and KM2 are contacts of high-voltage vacuum contactors, XS2 and XS3 are inverter output sockets, which use mine flameproof high-voltage connector sockets, XP2 and XP3 are inverter output cable plugs, which use mine flameproof high-voltage connector plugs. The inverter uses a mine flameproof high-voltage connector to achieve rapid connection and separation between the cable and the inverter, making the installation and maintenance of the inverter simple, fast and efficient. The output ends of power units A1 to A4 are connected in series to form U-phase voltage, the output ends of power units B1 to B4 are connected in series to form V-phase voltage, the output ends of power units C1 to C4 are connected in series to form W-phase voltage, and the output ends L1 of power units A1, B1 and C1 are connected together to form the midpoint of the inverter. The output ends L2 of power units A4, B4 and C4 are connected to KM1 and KM2 respectively. By controlling the connection and disconnection of KM1 and KM2, two operation modes of the inverter are realized: Mode 1, control KM1 to connect and KM2 to disconnect, and the inverter drives one motor; Mode 2, control KM1 to connect and KM2 to connect, the inverter realizes two-way output and drives two motors at the same time; the power unit has six-phase input, the line voltage is 690V, the output is single-phase, and the line voltage is 1380V. The use of 1380V output voltage reduces the number of inverter power units from the conventional 27 or 24 to 12. By adopting this type of power unit, the cabinet design of this type of inverter is smaller and has a higher power density.

[0025] A11 to C83 are connecting cables connecting the power unit and the secondary winding of the rectifier phase-shifting transformer. Each cable contains 3 core wires. The rated working voltage between the core wires is 690V, and the rated working voltage of the core wire to ground is 10kV.

[0026] like Figure 2As shown, 1 is the control and cooling cavity of the inverter, 3 is the power unit cavity, 4 is the rectifier phase-shifting transformer cavity, 5 is the control unit of the inverter, 8 is the internal cooling unit of the inverter, 9 is the power unit, 10 is the rectifier phase-shifting transformer, and 11 is the high-voltage vacuum contactor and current detection components.

[0027] A cable through hole is designed on the partition between the power unit cavity 3 and the rectifier phase-shifting transformer cavity 4, and the connecting cable connecting the power unit and the secondary winding of the rectifier phase-shifting transformer can pass through this through hole for connection. Because the power unit and the rectifier phase-shifting transformer are placed in the same flameproof cavity, ordinary non-flameproof cables can meet the requirements.

[0028] The power units in the power unit cavity are placed in three columns. The left column is U-phase power units connected in series, which are A1, A2, A3, and A4 from bottom to top. The middle column is V-phase power units connected in series, which are B1, B2, B3, and B4 from bottom to top. The right column is W-phase power units connected in series, which are C1, C2, C3, and C4 from bottom to top. There is an insulating part on the left side of the U phase, an insulating part between the U phase and the V phase, an insulating part between the V phase and the W phase, and an insulating part on the right side of the W phase.

[0029] The cooling water system of the flameproof high-voltage inverter for mining according to the embodiment of the present invention is as follows Figure 3 As shown, it includes an inner water circulation system and an outer water circulation system, and the inner water circulation system and the outer water circulation system exchange heat through a water-water plate heat exchanger S.

[0030] The external water circulation system includes a water inlet flange interface F1 and a water outlet flange interface F2; the water inlet flange interface F1 and the water outlet flange interface F2 are arranged on the side wall of the explosion-proof housing and are respectively connected to the water source of the external cooling water.

[0031] The transformer cooling device is installed in the transformer cavity, including a fan F and a hot air water cooling radiator R. The phase-shifting transformer T, the fan F and the hot air water cooling radiator R are arranged in the air duct inside the transformer cavity, and the water channel of the hot air water cooling radiator R is connected in series to the water channel of the external water circulation system.

[0032] The water inlet flange interface F1 is connected to the external circulation water inlet of the water-water plate heat exchanger S, the external circulation water outlet of the water-water plate heat exchanger S is connected to the water inlet of the hot air water cooling radiator R, and the water outlet of the hot air water cooling radiator R is connected to the water outlet flange interface F2, which together with the external cooling water source constitute the external circulation of cooling water.

[0033] The internal water circulation system includes an internal circulation water pump P and a frequency converter water cooling radiator. The internal circulation water outlet of the water-water plate heat exchanger S is connected to the inlet of the internal circulation water pump P.

[0034] Each power unit includes a radiator B for cooling power components. The radiators B of 12 power units are connected in parallel to form a water-cooled radiator for the inverter. The outlet of the internal circulation water pump P is connected to the internal circulation water inlet of the water-water plate heat exchanger S through the water channel of the 12 power unit radiators B connected in parallel. The heat of the radiators of the 12 power units is brought to the water-water plate heat exchanger S in the internal water circulation system through the circulating deionized water in the internal water circulation system, and is transferred to the external water circulation system through the water-water plate heat exchanger S, and then dissipated to the common external cooling water by the external water circulation system. The water-water plate heat exchanger S and the internal circulation water pump P are arranged in the control and cooling chamber 1 of the inverter.

[0035] The heat of the phase-shifting transformer is carried to the air-water heat exchanger by the circulating air through the circulating air duct, and the heat is transferred through the air-water heat exchanger, and the heat is taken away by the external ordinary cooling water flowing through the hot air water-cooled radiator.

[0036] The above embodiments of the present invention use a water-cooled power unit, which makes the radiator of the water-cooled power unit smaller, thereby reducing the volume of the power unit and increasing the power density. The phase-shifting transformer adopts an air-water heat exchange cooling method, which solves the contradiction between volume and cost, making the cavity volume of the phase-shifting transformer smaller without significantly increasing the cost.

[0037] The power unit of the embodiment of the present invention includes two identical unit circuits, each of which includes a three-phase full-bridge rectifier circuit, a DC bus, a full-bridge inverter circuit, a switching power supply and a control board.

[0038] The output end of the three-phase full-bridge rectifier circuit is connected to the input end of the full-bridge inverter circuit through a DC bus, and the output end of the full-bridge inverter circuit is the AC output end of the unit circuit.

[0039] The input terminal of the switching power supply is connected to the DC bus, and the power input terminal of the control board is connected to the output terminal of the switching power supply.

[0040] The control signal input terminal of the unit circuit control board is externally connected to the control signal output terminal of the cascade type high voltage inverter main control board, and the four drive signal input terminals of the three-phase full-bridge rectifier circuit are respectively connected to the drive signal output terminals of the control board. The AC output terminals of the two unit circuits are connected in series as the AC output terminal of the power unit.

[0041] The AC input terminal of the three-phase full-bridge rectifier circuit of the first unit circuit is connected to the first three-phase AC power supply, and the AC input terminal of the three-phase full-bridge rectifier circuit of the second unit circuit is connected to the second three-phase AC power supply.

[0042] The midpoint of the first half bridge of the first unit circuit full bridge inverter circuit is connected to the first terminal of the AC output end of the power unit, and the midpoint of the first half bridge of the second unit circuit full bridge inverter circuit is connected to the second terminal of the AC output end of the power unit. The midpoint of the second half bridge of the first unit circuit full bridge inverter circuit is connected to the midpoint of the second half bridge of the second unit circuit full bridge inverter circuit.

[0043] The midpoint connection line of the second half bridge of the full-bridge inverter circuit of the two unit circuits is connected to the heat sink through a grounding resistor. The heat sink is shared by the two unit circuits and is used for heat dissipation and cooling of the power components of the main circuits of the two unit circuits.

[0044] The structure of the main circuit of the 1400V power unit of the embodiment of the present invention is as follows: Figure 4 As shown, it includes two AC 700V three-phase power supplies R1, S1, T1 and R2, S2, T2; two three-phase full-bridge rectifier modules BR1 and BR2; four input fuses F11, F12, F13, F14; two film capacitors E1 and E2; and two full-bridge inverter circuits IGBT1 and IGBT2.

[0045] The full-bridge inverter circuit IGBT1 includes two half-bridges IGBTL1 and IGBTL2; the full-bridge inverter circuit IGBT2 includes two half-bridges IGBTR1 and IGBTR2.

[0046] The input of the power unit is two AC 700V three-phase power supplies, one of which is 700V AC power supply R1, S1, T1 connected to the three-phase full-bridge rectifier module BR1 through fuses F11 and F12, and connected to the energy storage film capacitor E1 through the DC bus after rectification by BR1. The film capacitor E1 is connected to the IGBT half-bridge IGBTL1 and IGBTR1 at the rear stage, where the output of the half-bridge IGBTL1 is an AC output terminal L1 of the power unit, and the output end of the half-bridge IGBTR1 is connected to the output end of the half-bridge IGBTL2 on the other side. The midpoint of the connecting line between the half-bridge IGBTR1 and IGBTL2 is connected to the heat sink of the power unit through the grounding resistor R1. Another 700V AC power supply R2, S2, T2 is connected to the three-phase full-bridge rectifier module BR2 through fuses F13 and F14, and is connected to the energy storage film capacitor E2 through the DC bus after rectification by BR2, and is connected to the IGBT half-bridge IGBTL2 and IGBTR2 after passing through the film capacitor E2, wherein the output of the half-bridge IGBTR2 is another AC output terminal L2 of the power unit, and the output end of the half-bridge IGBTL2 is connected to the output end of the half-bridge IGBTR1 on the other side. The sum of the two AC power supplies output by the output terminals L1 and L2 of the power unit in the embodiment of the present invention is 1400V.

[0047] The main circuit input of the power unit in this embodiment is two AC 700V three-phase power supplies, and the output is 1400V. The bus voltage of the main circuit is 989V, which is less than 1000V, and low-voltage power devices can be directly used. The three-phase full-bridge rectifier modules BR1 and BR2 of the power unit, and the four IGBT half-bridges IGBTL1, IGBTL2, IGBTR1, and IGBTR2 are uniformly installed on the integral heat sink of the power unit, and the switch tube is cooled by the heat sink. The connection point of the two half-bridges IGBTR 1 and IGBTL2 of the power unit is connected to the heat sink through the grounding resistor R1. The maximum voltage difference between the two power supplies and the heat sink is 989V. Therefore, the power devices of the main circuit can use low-voltage power devices, and electrical insulation only needs to be at a low voltage level.

[0048] The electrical principle of the 1400V power unit control circuit of this embodiment is as follows Figure 5 As shown, it includes: two switching power supply boards (switching power supply 1 and switching power supply 2); and two control boards (control board 1 and control board 2).

[0049] The input of the switching power supply 1 is connected to the DC bus voltage DC1+ and DC1- of the first unit circuit, and the output of the switching power supply 1 supplies power to the control board 1. The control chip of the control board 1 drives the four switch tubes of the full-bridge inverter circuit IGBT1 (two half-bridges IGBTL1 and IGBTR1). The input of the switching power supply 2 is connected to the DC bus voltage DC2+ and DC2- of the first unit circuit, and the output of the switching power supply 2 supplies power to the control board 2. The control chip of the control board 2 drives the four switch tubes of the full-bridge inverter circuit IGBT2 (two half-bridges IGBTL2 and IGBTR2). The main control board of the cascaded high-voltage inverter communicates with the two control boards of the power unit. The two control boards of the power unit output PWM waveforms. The PWM waveforms output by the two control boards control the opening and closing of the switch tubes of the two full-bridge inverter circuits IGBT1 and IGBT2 (4 IGBT half-bridges IGBTL1, IGBTL2, IGBTR1, IGBTR2). The output waveform of the first full-bridge inverter circuit IGBT1 has a certain phase difference with the output waveform of the second full-bridge inverter circuit IGBT2, so that the output voltage of the power unit output terminals L1 and L2 is an adjustable single-phase multi-level voltage waveform. By adjusting the phase difference and output frequency of the output waveform of the first full-bridge inverter circuit IGBT1 and the output waveform of the second full-bridge inverter circuit IGBT2, the output voltage of L1 and L2 of the power unit reaches 1400V.

[0050] The main circuit structure of the 1400V power unit in the above embodiment of the present invention not only provides a high-quality solution for miniaturization of the power unit, but also reduces the number of power units in the whole machine, and provides an effective solution for the integration and miniaturization of the entire high-voltage variable frequency speed regulator.

Claims

1. A flameproof high-voltage inverter for mining, comprising an explosion-proof housing, a phase-shifting transformer, a conversion circuit, a control unit and a cooling system, wherein the conversion circuit comprises a plurality of power units connected in series, and the AC input end of the power unit is connected to the three-phase output end of the low-voltage side of the phase-shifting transformer through a cable, characterized in that: The explosion-proof housing includes a transformer cavity, a power unit cavity and a control and cooling cavity in sequence along the longitudinal direction, and the phase-shifting transformer, the conversion circuit and the control unit are respectively arranged in the corresponding transformer cavity, the power unit cavity and the control and cooling cavity; the partition between the transformer cavity and the power unit cavity includes a cable through-hole, and the cable passes through the cable through-hole to connect the phase-shifting transformer and the power unit; the control unit and some components of the cooling system are arranged in the control and cooling cavity; the cooling system includes an internal water circulation system, an external water circulation system and a transformer cooling device, and the internal water circulation system and the external water circulation system exchange heat through a water-water plate heat exchanger; the transformer cooling device is installed in the transformer cavity, and the water path of the transformer cooling device is connected in series to the water path of the external water circulation system; the transformer cooling device includes a fan and a hot air water-cooled radiator, and the phase-shifting transformer, the fan and the hot air water-cooled radiator are arranged in the air duct inside the transformer cavity, and the water channel of the hot air water-cooled radiator is connected in series to the water channel of the external water circulation system. In the water circuit of the water circulation system; the external water circulation system includes an inlet flange interface and an outlet flange interface; the inlet flange interface and the outlet flange interface are arranged on the side wall of the explosion-proof shell; the inlet flange interface is connected to the external circulation water inlet of the water-water plate heat exchanger, the external circulation water outlet of the water-water plate heat exchanger is connected to the water inlet of the hot air water-cooled radiator, and the water outlet of the hot air water-cooled radiator is connected to the outlet flange interface; the internal water circulation system includes an internal circulation water pump and a frequency converter water-cooled radiator, the internal circulation water outlet of the water-water plate heat exchanger is connected to the inlet of the internal circulation water pump, and the outlet of the internal circulation water pump is connected to the internal circulation water inlet of the water-water plate heat exchanger through the water channel of the frequency converter water-cooled radiator; the cooling water circulated in the internal water circulation system is deionized water; the power unit includes a radiator for cooling power components, and the radiator of the power unit is connected in parallel to form the frequency converter water-cooled radiator; the water-water plate heat exchanger and the internal circulation water pump are arranged in the control and cooling cavity.

2. The flameproof high-voltage inverter for mining according to claim 1, characterized in that: The output ends of multiple groups of power units connected in series are connected to two groups of output terminals of the high-voltage frequency converter through two groups of contactor contacts, and the two groups of contactor contacts are connected in parallel; the cable is a three-core non-explosion-proof cable, and each cable contains 3 core wires.

3. The flameproof high-voltage inverter for mining according to claim 1, characterized in that: The AC input end of the power unit is a six-phase input and the output is a single-phase; the power unit includes two unit circuits, the unit circuit includes a three-phase full-bridge rectifier circuit, a DC bus, a full-bridge inverter circuit and a control board, the output end of the three-phase full-bridge rectifier circuit is connected to the input end of the full-bridge inverter circuit through the DC bus, and the output end of the full-bridge inverter circuit is the AC output end of the unit circuit; the four drive signal input ends of the full-bridge inverter circuit are respectively connected to the drive signal output end of the control board; the AC output ends of the two unit circuits are connected in series as the AC output end of the power unit; the AC input end of the three-phase full-bridge rectifier circuit of the first unit circuit is connected to the first three-phase AC power supply, and the AC input end of the three-phase full-bridge rectifier circuit of the second unit circuit is connected to the second three-phase AC power supply.

4. The flameproof high-voltage inverter for mining according to claim 3, characterized in that: The midpoint of the first half bridge of the first unit circuit full-bridge inverter circuit is connected to the first terminal of the AC output end of the power unit, and the midpoint of the first half bridge of the second unit circuit full-bridge inverter circuit is connected to the second terminal of the AC output end of the power unit; the midpoint of the second half bridge of the first unit circuit full-bridge inverter circuit is connected to the midpoint of the second half bridge of the second unit circuit full-bridge inverter circuit.

5. The flameproof high-voltage inverter for mining according to claim 3, characterized in that: The power unit includes a heat sink for power components, and the heat sink is shared by two unit circuits; the midpoint of the second half bridge of the full-bridge inverter circuit of the first unit circuit is connected to the heat sink through a grounding resistor.

6. The flameproof high-voltage inverter for mining according to claim 3, characterized in that: The output voltage of the power unit is adjusted by adjusting the phase difference and output frequency of the AC outputs of the two unit circuits.

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