A customer is in the business of producing railway signaling systems consisting of the signal lights and the control and monitoring electronics for safe operation. The system handles inputs from trains, sensors along the railway tracks, the traffic managing systems, and ensures the signal lights for the trains accurately control the traffic.
Any failure or downtime can not only heavily disturb the traffic flow, but can also lead to disastrous scenarios. Therefore, safe operation and high reliability are of utmost im-portance in this application. The control boxes are mounted outside, along the rail tracks and therefore have to withstand demanding, environmental conditions. The boxes are hermetically sealed to protect the electronics against dust, moisture, and salt. No ventilation holes or fans can be used, so cooling is only based on natural convection inside the box.
Temperatures inside the box can go from -40°C to 70°C or higher. The customer had used a power solution designed for 100W, but only capable of delivering 50W of derated power at high temperatures. RECOM suggested a smaller and less expensive 50W converter qualified for up to 115°C (case temperature), and therefore, able to reliably deliver 50W at ambient temperatures of up to 70°C. The pre-mounted heatsink allowed for easy cooling of the device without the need for fans. The complete solution had to conform to EN50121-4 standard which specifies limits for emission and immunity of the signaling and telecommunications apparatus. It meant that an external EMC filter was required, but as the
RPA60-FW was already pre-certified to the EN61000- 4-2,-3,-4,-5 and -6 standards, only an additional test for EN61000-4-8 was required to show compliance.
In the system, additional isolated voltages were needed; 5V for isolated, digital interfaces and +/-9V for analog sensor systems. These voltages were generated from the 12V bus by compact,
isolated RECOM DC/DC converters. Fortunately, RECOM offers a great variety of solutions and power supply products that still meet all the challenges of this extremely demanding environmental application space.
The solution passed all the environmental tests, got the necessary railway approvals, and demonstrated zero defects. Hence, we continue to be the most reliable solution provider, with thousands of units in the field.
For a lower-power solution, we offer our customers a 40W, sister part with the same qualification data, but reduced maximum power and output current.
