Application of the hottest VLT series inverter in

The application of VLT series inverter in VAV air conditioning system

the application of Danfoss VLT series inverter in VAV air conditioning system

safety, efficiency, comfort, health, flexibility and convenience are people's comprehensive requirements for modern buildings. To meet the above requirements, we cannot do without the support of modern technologies such as building automation, office automation, network technology, intelligent communication, intelligent fire prevention, intelligent security, and generic cabling. VAV air conditioning system is the latest air conditioning technology that integrates comfort, health, efficiency and energy conservation. It is not only talked about by architectural experts, but also favored by the majority of users. Modern buildings using VAV air conditioning system are growing day by day, such as bamboo shoots after rain. It not only brings people a comfortable and healthy environment, but also enables users to obtain huge economic benefits

the building of the external liaison department of the CPC Central Committee, located in the south of Muxidi bridge on Chang'an Street, Beijing. The building is equipped with variable air volume air conditioning system with excellent performance and perfect functions. Completely eliminate the disadvantages of fan coil unit and decentralized heat exchange. This modern building, with a total height of 17 floors and a total area of 68000 square meters, was put into operation in June 2004 and has achieved good results. In this system, VAV box of VAV terminal regulation box is widely used, which greatly increases the flexibility of the system and the comfort of the room. It is said that this is the first case in China. The ventilation system with variable frequency governor to adjust the air volume greatly improves the efficiency of the air conditioning system. The building uses 61 Danfoss vlt6000 series variable frequency governors, which are respectively used for the flow regulation of fans on each floor. The VLT converter with excellent performance has laid a solid foundation for the stable operation of the control system. In particular, the excellent electromagnetic compatibility conditions of VLT frequency converter provide necessary conditions for the safe operation of the control system, communication system, computer system and security monitoring system of the whole building

in this building, except for the refrigeration station, all electrical equipment used in the building are controlled by the central control station according to the schedule (a clock control mode). Fully automatic operation and local manual intervention are allowed. Its communication control system is a Two-level Network plus DDC control, which is composed of American Andover products, as shown in Figure 1. In Figure 1, the central control station is composed of three primary stations and five secondary stations. DD if there is a problem in one link in the experimental process, the C controller is distributed in each site (room and other controlled points) as a tertiary station. The primary station and the secondary station are connected by Ethernet (ether net): the connection between the secondary station and the tertiary station is composed of the intranet of Andover company. The double line, high-speed (12MB) intranet makes the huge control system operate flexibly and orderly, and the tertiary station controls the field equipment in the form of DDC

Figure 2 shows the connection diagram between DDC controller and VLT variable frequency speed regulator a B C. 4 it can be seen from the figure that DDC controls the frequency converter according to the bus setting and after testing the parameters such as pipe air pressure, so as to change the flow of the fan. See Figure 3 for the installation of transmitter feedback signals of various sensors, the mode of heat exchange, air flow control and direction of air flow movement, and the schematic diagram of the air cabinet given. It can be seen from the figure that this VAV control mode integrates air volume, air pressure, temperature and humidity, heat exchange and fresh air control. Compared with the traditional fan coil decentralized heat exchange mode in the past, it has the advantages of high efficiency, low consumption, good air quality, no customer leakage, convenient control and so on. It is worth pointing out that this way of controlling the fan by frequency conversion, adjusting the flow and achieving constant pressure and variable flow by Ma has a high energy-saving effect. The speed regulation signal varies with regions, and its power saving effect can reach 30%-50%. There are 82 above-mentioned air cabinets in the whole system, which are distributed on all floors. So many VAV air cabinets will bring considerable economic benefits as shown in Figure 2

it must be pointed out that the frequency converter is the connecting equipment of high-power switching frequency converter. In its operation, it will inevitably produce longitudinal interference and radio frequency interference. This technical indication, collectively referred to as "electromagnetic compatibility conditions", is of great significance for modern buildings that use a large number of plastic granulator industries and should constantly improve the technical level of the frequency converter, Its performance is an important factor that directly affects the stable operation of the whole control system. It also has an important impact on the quality and speed of system commissioning. Therefore, in the VAV control system, when designing and selecting the type of variable frequency governor, we must pay full attention to its electromagnetic compatibility conditions to avoid all kinds of interference problems caused by it, especially under the condition of a large number of applications of frequency converters, it will be very difficult to deal with the interference caused by poor electromagnetic compatibility conditions, so as to improve the safety and environmental protection performance of plastic packaging