Variable speed drives (VSDs) are increasingly being used for controlling motors, and one of the major reasons is their energy saving capacity. These drives often have specific ventilation requirements when they are mounted inside cabinets, and this can compromise the weather protection (IP rating) in outdoor applications.
Why is ventilation important?
Typically, a variable speed drive will generate a lot of heat in relation to its size. When a cabinet is not ventilated, the drive may overheat, resulting in the respective motor shutting off, and potentially damaging the VSD and components.
What’s the best IP rating achievable with fitted cabinet ventilation?
Installing a standard fan for ventilation with filters and grilles will lower the IP rating down to IP54, or less. It’s also possible to fit shrouds over ventilation grilles, which greatly limits the possibility of water ingress coming from above, resulting in a maximum IP rating of IP56. This option is generally appropriate for outdoor environments.
What other options are there?
The majority of VSD brands offer models for mounting outside switchboards with a IP54 rating or higher. Using these drives can remove the need for ventilation, allowing the switchboard’s IP rating to increase to IP66, for example. Don’t forget, however, that even VSD’s or other components which are rated to IP54 and above, are not necessarily suitable for mounting outdoors, particularly considering Australia’s weather conditions. A sufficiently sized cabinet can allow for enough heat transfer in some applications that have smaller VSD’s, meaning ventilation is not needed.