EMC & Thermal Management
Busting myths about electrical enclosures W
By Simon Brammer, product sales engineer of thermal management at Axair Fans
hilst we know that the electrical components that cabinets house must be ventilated to avoid
temperature and humidity problems, there are a number of misconceptions about enclosures. We bust the most common four myths below.
1. Internal components can be placed anywhere inside the enclosure It is often tempting to position electrical equipment where it is most convenient and comfortable for the installer. Sometimes this means clustering equipment at mid-height. However, it is imperative to carefully choose the position of the components to ensure a distance that allows correct for the circulation of air and proper distribution of power loads. By doing so, not only will this save energy in ventilation but unwanted hot spots and loss of thermal inefficiency can be avoided.
2. Electrical enclosures are always dry because they are sealed It is true that, with the correct enclosure ventilation accessories rated for ingress protection, electrical cabinets can achieve a water-tight seal. However, this does not take into account that condensation may
form inside the panel, due to rapid temperature drop below the dew point. This is due to changes in temperature outside of the enclosure, for example, at night when temperatures drop or equipment is shutdown. To avoid this, we need to heat the
cabinet with one or more anti- condensation heaters, especially during machine shutdown or in cold rooms. Additionally, a pressure compensation device (or vent plug) is recommended to prevent condensation forming inside the enclosure as a result of humid air entering through door seals due to a negative internal pressure (caused by forced ventilation). It does this by preventing the ingress of dust and water (rated IP55), whilst allowing the humid air to escape through a membrane. Thus, achieving pressure equalisation within the enclosure. Condensation reduces the reliability and lifetime of electrical and electronic equipment, causing serious malfunctions.
3. Electrical enclosures resist dust Whilst cabinets reduce the amount of dirt and dust that the equipment is exposed to, they are not completely dust-free. Steps can be taken to increase the degree of protection against dust, for example,
ensure the ventilation exhaust and fans have a high IP rating. The panel and its
components
must have an appropriate degree of protection suitable for the conditions of use. Furthermore, a regular cleaning and maintenance routine should be put in place. This should include the washing of or replacement of soiled filter media for filter fans and washing surfaces for sanitation, particularly in the food and beverage industry. Allowing dust and dirt to settle on electrical components may
compromise their functioning, especially if there are oils or condensates that cause moisture and prevent effective cooling.
4. Filter Fans always reduce the internal temperature of the enclosure In some circumstances, a filter fan is not enough to cool the cabinet. When the outside temperature is higher than 40°C, ventilation is not enough and heat penetrates through the filter grid, increasing the panel’s internal temperature. It is, therefore, advisable to choose an active cooling solution such a thermoelectric unit under these conditions.
axair-fans.co.uk
14 June 2019
Components in Electronics
www.cieonline.co.uk
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