Brief introduction of the hottest high voltage var

2022-08-18
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In recent years, as the main product of energy conservation and consumption reduction, high-voltage variable-frequency equipment has been widely used in many fields of the national economy (such as cement, chemical industry, petroleum, metallurgy, power generation, coal mining and other industries), and is playing an increasingly important role

because the power electronic power devices in the frequency converter will generate heat during normal operation, and these heat will be lost in the cabinet, which will eventually increase the temperature in the frequency converter; At the same time, it is cheap and light. At the same time, the shell temperature of power electronic power devices when they are in normal operation cannot exceed 85 ℃. If the temperature is too high, the frequency converter will be overheated and automatically trip. This requires that the design must ensure that the internal temperature of the cabinet of the high-voltage frequency conversion equipment is below 65 ℃ to ensure that the high-voltage frequency conversion equipment is in a normal and stable working state. In order to reduce the temperature in the cabinet, it is necessary to take some cooling measures at least reaching level 1

I. Introduction to traditional cooling methods

there are three traditional cooling methods:

mode I

it can be seen from the figure that the cold air required in mode I and mode II enters from the outside. Because high-voltage frequency converters are mainly used in industries with high pollution, such as cement, steel, chemical industry, power plants, coal mines, etc., there is a lot of dust in the outdoor air. When using frequency converters, they need to be removed, cleaned and ventilated more often. At this time, they need to be removed for ventilation and good cooling effect can be guaranteed. Therefore, although these two methods are simple in construction and low in cost, they have a large amount of maintenance, and can not completely ensure that dust does not enter the cabinet, pollute the electronic devices in the cabinet, and shorten their service life

mode 2

mode 3 is to install the frequency converter in a sealed room, and use the air conditioner to cool the indoor air, so as to ensure that the working temperature of the power electronic power devices in the frequency converter cabinet is within the required range. The advantage of this method is efficient refrigeration and no pollution, but it needs to build a house for the frequency converter and install an air conditioning unit during installation, which is costly

mode 3

in addition, there is another way to solve the heat dissipation problem in the power unit cabinet of the high-voltage inverter, which is to use water cooling. However, the water-cooling method also has its disadvantages: because the water pipes are installed near the power unit, it is very inconvenient to plug and unplug the power supply of the power unit; There are also serious hidden dangers of pipeline leakage, and the operation is also very inconvenient. Moreover, the operation of the high-voltage frequency conversion equipment will ionize the cooling water and produce many ions. In order to ensure the electrical insulation of the equipment and personal safety, the water ion adsorber device has become an auxiliary device that must be added. In this way, the cost will be increased, and the installation and maintenance will be cumbersome

II. Introduction to air-water cooling system

based on the comprehensive analysis of the above methods, an air-water cooling system is produced. Figure 4 and figure 5 as follows:

air water cooling system

Figure 5 structure of heat exchanger of air water cooling system

1. Working principle

this system is mainly composed of air duct, axial flow fan and heat exchanger. The wind direction is: Indoor - → frequency converter - → fan - → air duct - → axial flow fan - → heat exchanger - → indoor - → frequency converter. That is, the indoor air enters the frequency converter, flows through the electrical module that needs to be cooled, is discharged through the fan on the top of the cabinet, passes through the air duct and is blown to the heat exchanger under the air supply action of the axial flow fan (the copper pipe passes through the heat dissipation fin), and the copper pipe of the heat exchanger flows into the cold water with a pH value of 7 that has no corrosive effect on the copper pipe and a temperature lower than 30 ℃. After the hot air passes through the heat dissipation fin, the heat is transferred to the cold water, and its heat is taken away by the circulating cooling water, The cold air is blown out from the heat sink and sent to the enclosed room where the frequency converter is installed through the air duct in the fatigue test with a negative stress amplitude ratio (i.e. zero crossing). Ensure that the ambient temperature in the installation space of the frequency converter is not higher than 45 ℃, so as to ensure that the air temperature entering the frequency converter cabinet is not higher than 45 ℃

2. Installation requirements

an independent room is required during installation, and one side of the frequency converter is required to be 0.8m-1.6m away from the inner side of the outer wall; According to the actual situation on site, the operating surface (i.e. the front of the converter cabinet) can either face the cold air inlet or back to the air inlet as shown in the figure; The heat exchanger is installed in the wall, the cold air outlet faces indoors, and the axial flow fan and air duct are installed outdoors

3. Features

(1) the air duct is directly connected with the exhaust port on the top of the cabinet of the frequency converter, which improves the equipment operation efficiency of the cooling system and can directly cool the hot gas discharged by the frequency converter

(2) the serious accidents of water leakage and safe operation of high-pressure equipment after the distribution of cooling water lines in the high-pressure room are avoided

(3) the circulating air for heat exchange in the sealed space formed by the circulating cooling air device can maintain its cleanliness and is not polluted by the external environment

(4) the structure of the device is simple and practical, and the cost of manufacturing, use and maintenance is low

the device makes full use of the heat dissipation path of the existing high-voltage frequency conversion equipment, and there is no need to carry out large-scale technical transformation of the existing high-voltage frequency conversion equipment. As long as an axial flow fan, a heat exchanger and ventilation connecting pipe are configured, it can better solve the various defects of the existing high-voltage frequency conversion equipment in heat dissipation technology. The operation of the device will not be affected by the environmental pollution of its main application occasions - heavy chemical industry, nor will it produce new pollution to the surrounding environment, which is conducive to the protection of high-voltage frequency conversion equipment and the extension of the service life of its electronic devices. The high-temperature water in the heat exchange cabinet can be comprehensively utilized as an energy source with remarkable efficiency

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