When selecting a DC/DC converter for railway applications, you might think that once you’ve found the device with the right input voltage range, output power, efficiency and isolation characteristics, your job is done. However, there are other factors to keep in mind when ordering your part, which may add components to your design and affect space. Here are two conditions to consider:
Avoid Thermal Issues and RFI
DC/DC converters may play an important role within the railcar, but the operating environment is anything but hospitable to them. For instance, DC/DC converters may be subject to extreme temperatures and poor airflow aboard railcars, or those with high power densities may require additional heat removal to ensure a consistent surface temperature.
Railway applications also present many opportunities for signal disturbances that can affect the operation of various devices. This is why it’s important that DC/DC converters are tested to meet EMC (electromagnetic compatibility) standards. The International Electrotechnical Commission created the EN61000 family of EMC immunity standards for equipment subject to radio frequency emissions (RFI). They include ESD (EN61000-4-2), radiated immunity (EN61000-3) fast transients (EN61000-4-4), surges (EN61000-4-5) and conducted immunity (EN61000-4-6). In addition, EN55032 establishes EMC standards for information technology equipment.
Go the Extra Mile With Your DC/DC Converter Manufacturer
Be sure to ask your vendor about the optimal cooling method for the DC/DC converter you choose. Polytron Devices can provide optional heat sinks to many of its power products, such as the LWB40 Series single and dual output 40-watt DC/DC converter modules with a wide 4:1 input voltage range that’s ideal for railway applications. This DC/DC converter has a 115°C over-temperature rating.
Your vendor’s datasheet also should indicate whether the converter has been tested for compliance to various EN61000 immunity standards. The LWB40 Series features a six-sided continuous metal shield which minimizes conducted and radiated noise, and it meets EN61000-4-2 through -6 — including EN61000-4-4 and EN61000-4-5 when used with the required external input components. The series also satisfies the new EN55032 requirements. While many DC/DC converters may have the specifications you seek for your railway application, consider them a starting point. Additional diligence can give you greater peace of mind.
For more information about the LWB40 Series DC/DC converters, visit the product page.