RAC3.5-K/277 Series

Although some of our DC/DC converters contain Class A or Class B EMC filters built in, many of our low cost DC/DC converters contain only simple input filters. The customer can then decide to add an EMC filter individually or for all of the converters together to save costs. External EMI filter suggestions are given in our Application Notes for both Class A and Class B levels. All of our AC/DC converters contain a built-in Class B EMC filter as standard.

The UKCA (UK Conformity Assessed) marking is a new UK product marking that is used for products being placed on the market in Great Britain (England, Wales and Scotland). It applies to the same products that are currently CE marked. The circumstances in which self-declaration of conformity for UKCA marking can be used are the same as for CE marking. Based on current UK rules, RECOM is eligible to self-declare for the UKCA Declaration of Conformity (DoC) as long as the EU and UK regulations remain aligned.
RECOM will make available a separate UKCA Declaration of Conformity (DoC) based on the existing CE Declaration of Conformity (DoC) and test reports (self-declaration). CE marking remains valid for goods placed on the market in Great Britain until 1 January 2023. The UKCA marking must be used for placing goods on the market in Great Britain after this date. RECOM will continue to actively monitor any changes to the UKCA rules based on UK government guidance and react accordingly.
We will also instigate a program to successively add the UKCA mark to our CE marked products to fulfil our obligations as manufacturer. For further information or enquiries regarding our UKCA policy, contact TechSupport

RECOM prides itself on having a comprehensive certification portfolio, with full third party UL/IEC/EN certifications (not just 'designed to meet'). Certifications cover Industrial, Medical, LED lighting, Household, Railway and Automotive standards, depending on the application area of the converter.

We provide many medical grade converters with UL/IEC/ EN-60601-1 certifications (3rd Ed.), including risk assessment documentation.

The inrush current is dependent on the converter, the load (especially the capacitive load) and the impedance of the primary power supply. Therefore, there is no recommended value for the inrush limiting inductor as this need to be individually worked out for each application. Having said that, usually 22µH~100µH is a good starting point.
A CMC is a good inrush current limiter because the core does not go into saturation with high currents (the +ve inrush current is balanced out by the -ve inrush current), so it has a dual purpose: EMC filter and inrush limiting. However, for high power converters it is sometimes better to use a low inductance, high current, choke that is selected to reduce inrush rather than a high inductance choke selected for the best EMC filtering because otherwise too much power could be lost through the choke's resistance during normal operation.

Our AC/DC converters usually incorporate input surge protection, although some series require an external suppression MOV to meet all operating conditions. Our DC/DC converters do not usually incorporate surge protection, although an electrolytic capacitor placed close to the input pins is usually sufficient to meet the requirements of 61000-4-5.

RECOM prides itself on having comprehensive datasheets, but there may be a parameter or operating characteristic that it not listed.

We offer local Technical Support through our offices in Austria, Germany, USA, Singapore, Japan and China, or you can contact your local RECOM contact or distributor to ask us for more information.

All RECOM products will not be damaged if used without s load, although in some families some specifications may be out of range below 10% load.

The converters are not vacuum potted because we use a special process to remove the air bubbles (voids). The epoxy potting process is as follows:
1- The two-component epoxy is mixed and placed under a vacuum for 1 minute to remove any air bubbles created by the mixing process.
2- The plastic case is 1/3 filled and allowed to rest.
3- The pre-tested converter pcb is inserted into the case and 2/3 filled and allowed to rest.
4- The part completed converters are placed in a warm oven (30°C) for 20 minutes to allow any air bubbles to rise to the top.
5- The case is sealed with a harder grade of epoxy and baked at 50°C for one hour to cure.
6- In addition, spot checks are made with our X-ray machine to monitor and ensure that air voids are not present in any of our converters.
The silicone rubber potting process is as follows:
1- The pre-mixed silicone rubber compound is injected into the case
2- The case is placed on to a shaker and vibrated to encourage any air bubbles to rise to the surface
3- The case is topped up to the fill level
4- The converters are put aside to cure at room temperature.

The current drawn by the converter when it is idle (not loaded). All converters contain oscillators that absorb power even if no power is being drawn from the converter.

At a certain ambient temperature the internal heat dissipation makes it impossible for the converter to supply 100% of its power and the load must be derated (reduced) as the temperature goes higher. The derating curve shows the maximum power that the converter can deliver over the full operating temperature range. Some AC/DC converters allso have a low-temperature derating. This is due to increased losses caused by reduced efficiency at very low temperatures.

Yes, if they are derated (not used at full power). However, the simpler low cost converters have no overtemperature protection. If they are used outside of the temperature specification for a long period of time, they may fail. Our higher power DC/DC and AC/DC converters are fitted with over temperature protection. If they overheat they will simply shut down.

The isolation voltage given in the datasheets is valid for 1 second flash test only. If an isolation barrier is required for longer or infinite time the Rated Working Voltage has to be used. Recom provides an isolation conversion calculator on the website to indicate the equivalence bewtween DC and AC isolation for 1s, 60s or continuous.
It is very important that you compare the same type of isolation when comparing our products with the competitors to avoid misunderstandings.