Integrated structure of medium and high voltage inverters

1 Introduction

In the prior art, the switching cabinet, control cabinet, transformer cabinet , and variable frequency power unit cabinet of the frequency converter are all independent cabinets, and their spatial layout is arranged in sequence. The switching cabinet is connected to the control cabinet and the transformer cabinet through cables and control lines respectively, and the variable frequency power unit cabinet is connected to the control cabinet and the transformer cabinet through control lines and cables respectively. Due to the layout of the existing structure, the connection lines between them are long and complex, which is not convenient for assembly and maintenance. The sequential arrangement makes the overall structure of the frequency converter large in size, large in floor space, high in cost, and low in power density.

2 Structural scheme 2.1 Overall structure The overall structural schematic diagram is shown in Figure 1. The overall structural layout schematic diagram is shown in Figure 2. The back axial view of the frequency converter cabinet is shown in Figure 3. The schematic diagram of the air duct flow direction of the series ventilation cooling system is shown in Figure 4. 2.2 Working Principle Figures 1, 2 and 3 are schematic diagrams of the structure of the embodiment of the medium- and high-voltage frequency converter of the present invention with an integrated structure , including a control unit 1, a frequency conversion power unit cavity 2, a switching unit 3 and a transformer unit cavity 4. The control unit 1 and the frequency conversion power unit cavity 2 are arranged on the left and right sides of the front of the frequency converter cabinet 5; the switching unit 3 and the transformer unit cavity 4 are arranged on the rear of the frequency converter cabinet 5 in a square layout with the controller unit 1 and the frequency conversion power unit cavity 2 in a front-to-back integrated structure.

Figure 1 Schematic diagram of the overall structure

Figure 2 Schematic diagram of overall structural layout

Figure 3 is the rear axial view of the inverter cabinet

Figure 4 Schematic diagram of the air duct flow direction of the series ventilation cooling system

The switching unit 3 is adjacent to the transformer unit cavity 4 and connected by a cable. The frequency conversion power unit 9 is adjacent to the transformer 6 and connected by plug-ins and short cables. The wiring between the units is simple and convenient, the length is shortened, and the cost is significantly reduced. The control unit 1 is connected to the frequency conversion power unit 9 by an optical fiber to transmit control signals, and has strong anti-interference ability.

The frequency conversion power unit cavity 2 adopts a drawer structure, including multiple power units 9, and three columns are set corresponding to the three phases. By configuring different numbers of power units 9 per phase, inverters with different capacities and different voltage levels can be produced.

In FIG4 , a ventilation and cooling system is provided between the variable frequency power unit cavity 2 and the transformer unit cavity 4, including an air duct 7 and a fan 8. The air duct 7 includes the variable frequency power unit cavity 2 and the transformer unit cavity 4. A partition 11 is provided between the variable frequency power unit cavity 2 and the transformer unit cavity 4. The transformer unit cavity 4 is also provided with a back plate 12. The fan 8 is arranged at the lower part of the transformer unit cavity 4. The inlet of the fan 8 is connected to the variable frequency power unit cavity 2, so that a negative pressure is formed in the variable frequency power unit cavity 2. The outlet of the fan 8 is arranged below the transformer unit cavity 4, so that a positive pressure is formed in the transformer unit cavity 4. The air inlet of the air duct 7 is arranged at the front part of the variable frequency power unit cavity 2. The wind enters the transformer unit cavity 4 after passing through the radiator of each power unit 9 and blows toward the transformer 6. The air outlet of the air duct 7 is arranged at the top of the transformer unit cavity 4 to take away the heat of the variable frequency power unit cavity 2 and the transformer unit cavity 4. In order to prevent rain from entering the air outlet of the air duct 7, a canopy 10 is provided on the top of the inverter cabinet 5.

3 Structural advantages Compared with the existing technology, the advantages of this structure are: (1) The control unit, variable frequency power unit, switching unit, and transformer unit adopt an integrated structure, with a front-to-back layout, compact structure, and only 1/3 of the volume of the split layout. The wiring between the cabinet units is simple and convenient, and the cost is significantly reduced; (2) The variable frequency power unit is installed vertically in a drawer structure, with each column corresponding to one phase, reducing the floor space; (3) The power unit is installed using a quick plug-in connection method, which is convenient for the production, storage, installation, expansion, maintenance and transportation of the power unit. It can be applied to the production of inverters of different capacities and different voltage levels, and has strong versatility; (4) Series ventilation is used between the transformer unit and the variable frequency power unit, which simplifies the cooling system. 4 Conclusion At present, the high-voltage variable frequency speed regulation system is a control and energy-saving system for large high-voltage motors. It is used in thermal power, steel, mining, coal, cement building materials, petrochemicals and other industries. It is the best choice for energy saving of large motors. It has the advantages of reducing power consumption, improving efficiency, reducing the impact on the power grid, and improving production processes. The integrated structure of medium-high voltage and medium-power inverters is a major innovation in inverter structure. This technology has been applied for patent protection. This technology has been put into practical application and has good results, and has application and promotion value.