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Customized sub-rack extension for CPU ventilation

Portfolio: Electronics
Industries: Electronics


In order to guarantee a very high level of reliability, usually no rotating components are permitted in railway technology, so that possible causes of damage are minimized.

A HEITEC customer had planned the use of a more powerful CPU for one of its existing systems in the railway sector. This significantly more powerful CPU had to be cooled due to the high heat dissipation. For this purpose, fans were to be used that were not provided in the previous system.

As a solution HEITEC designed a cost-effective, 1U high sheet metal housing, which can be used as an extension of the existing system. This allowed the customer to continue to use his existing rack in its entirety. The housing offers space for four axial fans that cool the CPU sufficiently. For railway applications, there are a number of requirements that the system must meet. One of these is the high shock and vibration resistance of the system. But even in the extended temperature range from -40°C to +85°C, the system must function perfectly and fail-safe. The mechanical stability was achieved through an application specific design. The requirements regarding environmental temperature were met through selection of appropriate components and conformal coating of the boards.

But also a good maintainability of this subrack extension for easy handling during operation was a prerequisite. HEITEC implemented this with an innovative design. The fan housing consists of only three parts that are screwed together. In addition, the filter mat can be changed easily without tools.

In this application, it was also necessary to develop a circuit that included an integrated temperature switch, among other things. This makes it possible that at a temperature below -20°C the fans are no longer supplied with voltage and damage to the fans caused by cold is prevented.


  • Customer specifi c stainless steel housing (V2A)
  • 4 axial fans 12 VDC
  • L x W x H: 240 mm x 84 TE x 1 U
  • Temperature switch-off for temperatures < -20°C
  • Shock and vibration resistant according EN 50155
  • Extended temperature range according EN 50155
  • DC wide range voltage input 14,4 – 154 VDC


  • Tailor-made system
  • High shock and vibration resistance
  • Extended temperature resistance from -40°C to +85°C
  • High reliability and service life
  • Good maintainability due to the use of only a small quantity of parts and fi lter mat that can be replaced without tools
  • Cost-optimized design
  • Fully Railway certifi ed reg. EN50155