HOW TO PROTECT DRIVES FROM POLLUTANTS
We’ve already discussed some of the other main causes of drive failure, such as overheating in this article, but build up of dust and dirt is also detrimental. It may seem unlikely, but your AC drives could be experiencing allergies and just like us humans, dust is one of the biggest causes.
Unfortunately most standard enclosure classifications of AC drives simply don't protect against dust. These AC drives have openings in the enclosure to allow air to flow over the components to keep them cool and ensure they're running efficiently. These openings don’t often include screens or filters and as a result this allows dust and other particulates to enter the drive as they are carried through by the air flow. This dust can then stick to the components of the drive which reduces the efficiency of heat exchange with the surrounding air. Additionally, since many AC drives are actively cooled, meaning that they use a fan to force air past the heatsink, dust can also build up on the blades of the fan which can cause an increase in overall wear and tear.
The makeup of the dust can also have differing impacts on your AC drives. For example very fine particles tend to cling to almost everything, especially if the region has regular high humidity levels, this can therefore create a paste like substance that can become hard and shell like. This can ultimately prevent direct contact with the cooling medium and the surrounding air. Other facilities where metal processing is the main focus can create conductive dust, this could cause a lot of problems in terms of improperly protected electronics.
Fluff and fibers
Although the word fluff doesn’t sound very intimidating, fluff in a drive is often a bigger problem than dust. So where are fluff and fibers most likely to occur? Industries such as textiles are most common, but you could also have a fiber problem in industries where materials like fiberglass are made.
Similar to dust, fluff is small enough to pass through the air flow channel of your AC drive if the air is unfiltered. Unlike dust, however, fluff is usually larger and can easily get caught on the heatsink and in the air filters. This can lead to a blockage of fluff that gets tangled and can almost completely block the airflow to the drive.
If enough fluff or fibers reach the fan they can reduce the fan’s cooling capability and prevent the fan from spinning as well as causing premature fan failures. This can lead to overheating and derating of the AC drive itself and ultimately reduces its operational lifetime. An accumulation of fluff inside the drive can produce hot spots and reduces creepage distance, resulting in a decrease of high voltage withstand level, especially in high humidity conditions therefore causing failures.
Filings are little pieces of material that fly off in the machining process. Most of the time filings are not a major concern, however when the filings are metallic it can cause problems. Filings could land on unprotected areas of equipment, in AC drives this runs the risk of sparks or a full short circuit if they land on the terminals. Whilst causing breakdown of a drive, this can also lead to damage of other electronic equipment nearby.
How to prevent contaminants entering your drive
There are a number of straightforward steps that you can take to ensure minimal exposure to dust, fluff and filings.
Installation in a clean room
One option is to ensure that all your AC drives are installed in a clean room away from dust, however this is not easy and not always possible.
Installing in a higher classified enclosure
This is the next best option to keep your drives safe from dust, fluff and filings. These types of installations still require you to draw air into the enclosure in order to provide proper cooling; having a filter on the inlet of the cooling air will help to minimise dust entering the enclosure. The type of enclosure you need will depend on the size and material of the contaminants that are present. See our guide to choosing the right IP rating for your drive for more details about what each IP rating protects against.
Many newer drives now come with PCBs and components coated to protect the circuitry from corrosive atmospheric conditions as well as a certain degree of dust. A lot of Danfoss drives from the VLT family are available with conformal coating.
Regardless of your AC drive selection and installation location, keeping a rigorous preventative maintenance routine will help ensure the longest possible life of your investment. If your AC drive has been installed in an enclosure with a filter, regularly changing the filter will ensure that dust is prevented from entering the drive as well as maintaining an appropriate air flow through the enclosure to help with cooling. On the other hand if your AC drive is not located in a clean enclosure, checking the air flow channels at regular intervals to make sure there is minimal or no dust build up can help to prolong the life of the drive.
Some installation environments make it difficult to perform visual inspections, in this case we recommend keeping an eye on the temperature of the drive as a significant increase in temperature could indicate a potential build up that prevents necessary cooling.
If you have any questions about what drive is suitable for your environment and best practice to get the most from your AC drive, get in touch with our team today.