Components and electronics in the switch cabinet are becoming increasingly compact while retaining the same switching function. However, this does not lead to a reduction in heat loss and cannot prevent the build-up of heat in the enclosure. On the contrary: heat-producing components add up and the heat increases continuously. The result: 'hot spots' are created. The service life of the components positioned in these hot spots is likely to decrease. In other words, a creeping heat death is pre-programmed. Ultimately, the components no longer deliver the desired performance, fail and cause the system or machine to come to a standstill. In short: Innovative components in the control cabinet usually have the negative consequence that cooling is increasingly required.

Is the use of a conventional cooling unit the solution? Up to now, cooling units have been dimensioned for an internal temperature in the enclosure of around 25 to 30 °C at the highest possible ambient temperature for the theoretically maximum required cooling capacity. This means that oversized cooling capacities are installed, but are usually not immediately required. The problem is exacerbated by global warming with its temperature peaks - even in temperate zones such as Germany.

Figure 1: Rear view of an Airstream frame with Airblade for targeted cooling air flow (bottom left) and Airblower for homogenizing the enclosure climate (top).

© Sagittarius

The solution to the problem is therefore not the use of an oversized cooling unit, but rather the development of an intelligent cooling air routing system in the enclosure (Figure 1). What such a solution concept can look like is illustrated below using the example of the so-called AirStream concept from Lütze. In addition to the wiring system, which is compatible with all standard enclosures, this concept includes an online configurator and an online tool for calculating the thermal performance and optimizing existing and newly planned enclosures.

Before the wiring frame is planned with the help of the online configurator, background information for the geometry and definition, such as the height, width or depth of the enclosure, must be collected. The wiring frame is individually adapted to the components. The frame itself consists of aluminum modules in which an additional level in the depth of the enclosure behind the components is used for the wiring. This means that there are no more unfavorable cable ducts in terms of ventilation. The frame can then be optimally adapted and can be planned online in just a few steps. The result of this planning is output in a file that can be imported into any CAD program. With the integration of the wiring system in the Eplan portal, designers also benefit from engineering tools such as project planning, 3D layout, production and assembly.

The web-based AirTemp application has recently been introduced to provide additional assistance in planning the wiring system. The thermal analysis tool enables quick and spontaneous analyses of different types of wiring and cooling systems and provides well-founded results on heat development and distribution in the enclosure. In other words, the heat simulator offers the possibility of a heat forecast that goes beyond a simple description of the current status and therefore allows the heat development in the enclosure to be determined as early as the design phase.

Among other things, the different temperature layers in the enclosure - whether with mounting plate or wiring system - can be precisely determined in this way. For this purpose, the enclosure is divided into three zones (top, middle, bottom). The temperature can be precisely defined in the zones. The user must first determine the key data. For example, whether the control cabinet is free-standing or mounted on a wall. Then all that needs to be entered is the power loss of the installed components. Based on this, the tool then provides data and information on, for example, how the arrangement of the components in the enclosure can be improved from a thermal point of view or how cooling options within the enclosure affect the enclosure. Ultimately, the aim must be to optimally position the components during the planning phase of the enclosure and thus increase efficiency.

Guide air flows precisely

A very efficient way to homogenize the climate in the enclosure or to ventilate heat pockets directly is to guide the air flows precisely via air baffles (AirBlades) in combination with corresponding fans (AirBlower). This significantly improves the heat dissipation performance of the enclosure. Practical experience shows that the temperature level in the enclosure can be equalized and reduced by up to 10 Kelvin within a few minutes.