What Does Plug & Play Mean in the Context of Railway Applications?
“Plug & play” refers to a product that fulfills all operational requirements for an application without additional effort from the user. For
railway applications, plug & play products must withstand harsh operating environments. Unlike consumer power supplies designed for the benign conditions of a home or office, a railway DC/DC converter must operate reliably for many years under extreme conditions such as heat, cold, shock, and vibration.
The converter must comply with EN50155 and all related standards, which define performance requirements for electronic equipment used in rolling stock—including locomotives, passenger wagons, light rail vehicles, and freight trains. EN50155 specifies minimum requirements for electrical and mechanical operating conditions, equipment reliability, and expected converter lifespan. These standards exceed the capabilities of typical “off-the-shelf” modular DC/DC converters.
For example, the nominal system voltage in a railway application can vary from +25% to -30%, with dips down to 60% of nominal and surges up to 140% of nominal. For a 110V nominal system, this corresponds to an input range of 77V–137.5V, potentially expanding to 66V–154V during dips and surges.
What Makes the RMD500-EW Plug & Play?
The RMD500-EW incorporates all features required by EN50155: reverse polarity protection, EMC and surge filtering, inrush current limiting, 10ms hold-up time, and output OR-ing diode. These features eliminate the need for additional external components.
The power supply meets all relevant rail environmental standards for conducted and radiated EMI, mechanical shock and vibration, thermal shock, temperature cycling, isolation coordination, and fire protection. With a wide 4:1 (43–154VDC) input range (170V peak) and 24V output with reinforced isolation based on 5.5mm air creepage distances (OVCIII / PDII), the RMD500-EW supports nominal 72V and 110VDC inputs within EN50155-prescribed tolerances and surges.
The output delivers 500W up to 95°C baseplate temperature without derating. This enables operation in ambient temperatures from -40°C to +70/85°C with natural convection cooling, meeting EN50155 OT4 (-40°C to +70°C) with ST1 and ST2 (+85°C) conditions. Efficiency reaches up to 95.5% even at light loads over a wide input range, allowing high power density in a compact 209 x 141 x 48mm package. The RMD500-EW can be mounted in any orientation, with screw terminals for convenient input and output connections.
The product is certified to EN 62368-1 and EN 50155 (S2) standards, with 3.5kVAC rated isolation. It is highly reliable, robust, and fully protected against short circuits, output over-voltage, over-current, and over-temperature conditions.
Internal Design & Railway System Integration
Figure 2 shows the internal block diagram of the RMD500-EW. The design uses a forward topology with an active clamp reset circuit to minimize switching losses and a secondary-side synchronous rectifier to ensure higher efficiency. Plug & play features include an integrated input filter, a reverse blocking diode, and a hold-up time module.
Other standard features include DC-OK volt-free relay contacts, remote ON/OFF, and active power sharing with OR-ing diodes for parallel operation when increased power or n+1 redundancy is required. The nominal 24V output voltage of the RMD500-EW can be trimmed between 19.2VDC and 25.2VDC by using an external tri resistor. The eco-friendly RMD family is designed without encapsulation and so the weight is considerably lesser than that of potted products.
If these do not meet the needs of a particular railway application, RECOM has extensive experience in custom designs that meet EN51055 requirements. The portfolio also includes rack-mounted AC/DC and DC/DC converters for rolling stock and trackside applications, from low power up to 18kW with DC, single-phase, or three-phase AC inputs. The battery charger families are designed as modular concepts. In the 1,5kW, 5kW, or 18kW class, all units are cascadable and can operate parallelly to increase the availability and reliability of the converters. They are ideal solutions for redundant n+1 power units, and for safety-relevant and reliable rolling stock applications. The battery chargers come with excellent efficiency and functionality features such as temperature-regulated output voltages and analog or digital interfaces.
To learn more—and to access a handy FAQ with helpful tips - visit the
RMD500-EW product page.
