Installing a fan to ventilate an electrical enclosure may seem to some as simply just another cost to cut. However, the cost of a proficient fan unit is near inconsequential when compared to the cost of the equipment, labour and interruption to replace a failed inverter. The overheating of expensive equipment through failing to provide active ventilation is by far the main cause of failure within electrical cabinets. In addition, effective ventilation significantly increases the lifespan and energy efficiency of equipment as well as protection from dust and water splashes (IP54)
A simple solution to enclosure ventilation and cooling is a combined fan and filter unit. Fan filter kits have been in use for around 20 years and are now considered ‘part of the scenery’ and used in a whole host of enclosures and cabinets to facilitate the effective running of the equipment it is housed in. Over this time their function has not changed, so in cooling the enclosure and its components their role is still as useful as ever, if not a vital part of the design of the system. However, if the wrong product is selected, the whole control cabinet may overheat and compromise not only the value of the equipment it contains, but also the panel’s primary function, powering a whole process plant, shopping centre or datacentre. The impact of this could be catastrophic so it pays to seek advice and assistance when selecting a system for your power electronics cooling.
Selecting a fan is often made to be more complicated and expensive than necessary with overblown software programs giving manufacturers specific solutions. The main points of consideration are the maximum ambient temperature that the components can tolerate and the equipment heat loss figures. A simple equation can then be used which takes into account the air density and then determines the required air volume flow rate.
For basic level cooling, the industry offers a range of fan filter units, for ease of installation these feature click-fit chevron louvered panels. As an example, Axair offer these in three different variants designed to filter air at various rates. The fitted fans should be of ball bearing construction and not sleeve and often neglected is the ease of which the filter media can be removed. The cover should be easy to remove to access the filter media, if the mechanism is not straight forward then this risks the probability that it will not get changed. Inevitably resulting in problems in the long run.
In a standard fan filter unit the fan sucks air into an enclosure, first through the louvre, then the filter. Warm air exits through a filter louvre, generally of the same dimensions as the inlet, but larger if necessary to improve the flow rate.
Where the required minimum flow rate is not available from an integrated fan and filter there is an enormous range of axial and centrifugal fans to choose from, either in standard form or within roof mounted units. In some cases it is possible to take a high performance fan and use it in conjunction with a number of standard filters, sized to achieve the ideal airflow whilst coping with the ingress protection requirement IP54 or IP55. For hot spot cooling you may look to use either frame axial fans or small centrifugal blowers.
Recent developments also mean that two additional fan solutions aimed at the control panel industry can be used, by using backward curved centrifugal motorised impellers either in ‘Reverse’ configuration or assembled as a ‘fan module’.
Backward curved centrifugal fans overcome high resistance to air flow and can operate without a space consuming scroll housing and crucially are pre-assembled for ease of mounting, saving time and cost. They also offer great versatility for door, wall or roof mounted installations. In enclosure ventilation EC fans are increasingly used due to recent European Directive requiring a minimum level of efficiency for fans of a power range from 125Wa to 5kWa. They offer energy saving while operating, but crucially, they tend to offer higher performance thanks to speed set up by electronic and not by the operating frequency. There is also an extensive range of double inlet centrifugal fans, particularly recommended for large heat sink cooling.
In summary there is an answer to every problem of enclosure ventilation but at the extreme there is a need to utilise or combine standard products to make special solutions. For full thermal management components including fan filters, heaters, thermostats and adaptors visit the Axair Fans online website www.axaironline.co.uk
With the UK recession causing an intense increase in market competition, many control panel builders tried to get ahead by reducing stock levels and adapting standard products to meet customer requirements. Despite reducing costs, streamlining the range of designs available has somewhat obvious limitations. Even with modification, customers can be restricted when it comes to specific requirements such as temperature control or prerequisites on space.
High power control panels are often densely packed with components and require a top mounted fan to power a higher airflow. Backward curved fans can often provide the solution by exhausting the hot air out of the control panel out to atmosphere. Occasionally a higher power fan is needed where the high power and heat load combined are too much for top mounted enclosures. Backward curved modular plug fans are suited to this high performance and can dissipate the heat effectively whilst taking up little space on top of the enclosure. Using high powered industrial fans such as the EC energy efficient GKHM EWheel ensures accurate power distribution enables designers to include the larger drivers they’re used to. Speed control ensures a constant airflow or controls the speed of the fan to effectively cool an enclosure whilst also allowing for additional or removed components in the enclosure.