How is the VFD installed in a civil structure?
In this post we look at the ways how to install VFD into a civil structure, meaning a building. What options exists and how do they differentiate?
3 ways of VFD installation
Variable frequency drive (VFD) typically is an indoor equipment. Thus, it needs to be integrated in a civil structure, be it a classical building (concrete, brick) or a pre-fabricated building (E-house). The rare solution of VFD installed outdoor is listed as well.
Here are the three ways of VFD installation:
A) Inside an electric room, part of concrete or brick building → VFD indoor
B) Inside an E-house / pre-fabricated building / container → VFD indoor
C) In a special outdoor enclosure → VFD outdoor
A) Electric room
This is likely the most common case, at least in Europe and Asia. The electric room is a part of an industrial building system, typically made out of bricks, steel or concrete. The electric room may not house just the VFDs. Switchgear, motor control center, low-voltage distribution panels, various control hardware such as PLCs or HMI panels etc can be installed in the same room. Thus, the electric room may vary from relative small room to a larger space.
Electric room shall be a clean room. It is expected to have a clean air (eventually filtered). All the infrastructure is available, such as heating or ventilation, cooling system (air or liquid), lighting system etc. The electric room is accessible for an authorized personnel. When the VFD has its own enclosure including door interlocking (which is typically the case), the personnel can enter the electric room while the equipment is energized. It can be used during commissioning, maintenance or troubleshooting.
B) Pre-fabricated building (E-house)
The option is used in a case where normal building is not available. Instead, the VFD is installed in a purpose built pre-fabricated building. In North America the structure is commonly called an ‘E-house’ while Europeans often call it a ‘container’ ¹. The word E-house or pre-fabricated building sound more appropriate. It is not a plain container like used for logistic purposes (on a container vessel or a truck). Instead, it is a structure that provides a separation from outdoor ambient, includes low-voltage distribution, lighting, heating or cooling etc. it is not just to house the equipment. The design of an e-house shall support easy installation and maintenance works (e.g. through removable cover or removable panels for maintenance access or replacement of components).
¹ The “container” shall not be mistaken with a sea freight container to ship goods. It is a structure that provides mechanical protection, but is also equipped with auxiliary power distribution, heating/ventilation/air conditioning system, lighting, cable trays for power cables, fire detection and extinguishing system, openings for maintenance access etc. It may feature an additional compartment with work station for a technician used during commissioning or testing with local control.
Container housing a VFD is typically not standardized in terms of outer dimensions in the way the containers for shipping of goods are standardized (e.g. 20′ or 40′ container).
The e-house may have an internal separation into a section for power hardware and sections for cooling or control (e.g. a work station used during commissioning or maintenance works).
E-house may be installed on the ground or elevated on a platform.
- Sitting directly on the ground
- Elevated on concrete pillars
- Elevated on a steel platform (pedestal)
C) VFD with special outdoor enclosure
This is a rare option. The VFD is equipped with a special enclosure that supports direct installation outdoors. It does not require any electric room or e-house. The enclosure is quite sophisticated. It shall decouple the VFD from changing outdoor environment. In the classification the enclosure is rated as NEMA 3R. Thus, the solution is often shortly labelled as NEMA 3R enclosure.
The option is typically limited to smaller air-cooled drives. The absence of e-house reduces the total cost. Another plus is a fast installation on site. However, for larger VFD power ratings in becomes impractical. Also, the installation is mostly not suitable for environments with high humidity or corrosivity. Total height is typically increased as there is space required for the handling of cooling air.
Summary
Inside an electric room
- Conventional solution
- Using an industrial building (concrete, brick, steel)
- Clean electric room, used to house VFD, switchgear and controlgear, MCC, LV distribution panels etc
In a pre-fabricated building (E-house)
- Engineered solution
- Used where industrial building is not available (e.g. remote areas with limited infrastructure)
- More frequent in North America; in Europe for utility installations (e.g. STATCOM)
- Purpose built to house the VFD
- Pre-installed equipment → fast installation on site
Special outdoor enclosure
- Special solution
- VFD installed outdoor, using outdoor rated climate-controlled enclosure
- Limited to air-cooled drives, only up to certain power
- Not suitable for corrosive environment
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References
[1] Enclosure protection, MB Drive Services, January 2022, available online, https://mb-drive-services.com/enclosure-protection/
[2] How to choose a medium voltage VFD: System integration, MB Drive Services, May 2021, available online, https://mb-drive-services.com/selecting-mv-vfd-system-integration/
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