Railway switch heater pre-installation test

Yesterday we successfully passed the pre-installation test of our railway switch heaters at the Austrian Federal Railway infrastructure unit (ÖBB-Infrastruktur AG). At 08:30 pm we showed up in the Vienna headquarters on Praterstern, met the responsible engineer and went to the testing workshop located nearby.

The workbench was too short, and so we had to to place the 2 meter long heater on the floor. In order to avoid heat sinks distorting the results, ÖBB staff put it on a bubble wrap foil. Wrapping paper was applied to the shiny stainless steel surface which otherwise would not allow for reliable measurements with the thermographic camera brought along.

Test setupThermographic image of switch heater







As a first step, ÖBB measured the isolation between ground and power cables which was 600 MOhm which was the maximum which the device could measure. Then they powered the heater with 225V DC and measured voltage, current, and surface temperature over a period of 25 minutes according to their test procedures.













At room temperature, the heater hat a power consumption of 350W which is exactly the nominal heating power of the device. Despite the fact that the surface is comprised of a 1 mm steel sheet, the heatup curve was very steep and after 2 minutes 50°C were reached. The target temperature range of 60-65°C was reached after 5 minutes already. In order to keep the device as robust and simple as possible and avoid the use of control units, we are using ATT Powerfilms based our E-type conductive ink with an extreme PTC curve. Above 60°C the resistance rises so sharply that the heatup stops without the use of electronics or bimetallic switches. The heater temperature stabilised exactly in the specified range and the power consumption at appr. 110W, only a third of the nominal power. As a final step, the isolation was measured again, which gave a result of 308 MOhm which is far above the minimum according to ÖBB requirements.

ÖBB seemed very impressed by our switch heaters, both by their performance (and in particular the intrinsic self-regulating function) and the quality of manufacturing. The successful pre-installation test qualified our product for use in switching systems, and as a next step they will be installed in switches along a much
-used railway line for winter testing. We will keep you posted about the results …

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