Undoubtedly, the most popular form of installation is to centrally install the VSD in the control cabinet. The advantage of centralized control cabinet technology lies in the protected installation of equipment and centralized access to them for power supply, control, maintenance and failure analysis.
When installing in the control cabinet, the main aspect that must be considered is thermal management, not only the thermal management of the equipment, but also the thermal management of the entire installation process. Due to heat dissipation in the control cabinet, additional cooling of the control cabinet may be required.
According to the installation regulations of the VSD manufacturer, a minimum distance must be maintained above and below the equipment and between the equipment and adjacent components. For better heat dissipation, it is recommended to install directly on the back wall of the control cabinet. Some manufacturers also specify the minimum distance between each unit. However, if possible, it is best to install the units side by side in order to effectively use the installation surface area.
In some cases, the disadvantage of centralized installation is the long cable length to the motor. Although the use of shielded cables will undoubtedly reduce the RFI effects of motor cables, these effects have not been completely eliminated.
As an alternative to centralized installation, you can also choose a decentralized layout to arrange facilities. The VSD is very close to or directly on the motor here.
Thereby reducing the length of the motor cable to a minimum. In addition, decentralized installation has advantages in fault detection because the relationship between the controller and its associated motor is easy to see. In a distributed configuration, a fieldbus is usually used to control the drive.
When planning a distributed installation, factors such as ambient temperature, main voltage drop, and motor cable length limitations must be considered. Important factors such as these are usually ignored in the advanced design of engineering projects.
For example, not only decentralized equipment but also power supply cables must be suitable for the installation environment. For example, fieldbus cables must be suitable for harsher environments and sometimes must be suitable for flexible types. In addition, avoid installing the equipment in hard-to-reach locations to ensure quick maintenance.
Another major consideration is the segmentation of decentralized networks. For economic reasons, it is beneficial to combine units into groups or segments. When determining which segments require other segments to operate and which segments can, must, may or should continue to operate autonomously, careful consideration must be given. For example, if certain chemical processes cannot be interrupted, the failure of low-level sections is not allowed to destroy important sections.
Finally, the expertise required to install a decentralized network should not be underestimated. In addition to understanding the fieldbus system used, the technician must also understand the structure (what happens to the entire system if a single unit fails) and the environmental conditions of the decentralized network, and must be able to estimate these effects.
Although decentralized equipment is always more expensive than centralized equipment, a well-conceived decentralized concept can save about 25% of the cost of centralized systems. Potential reasons for saving installation costs are the reduction of cable length and the use of equipment nodules to reduce nodules, which have been manufactured and tested by machine manufacturers or suppliers.
