Power Supply Basics

Why are black heatsinks better than silver?

Posted by Dulcie on January 19, 2012
Posted in: Power Supply Basics

By Martin Southam, Director of Marketing, TDK-Lambda EMEA

One of the most obvious differentiators of our new CFE400M digitally-controlled medical power supply is that the housing is black, rather than a more usual plated or brushed metal finish. Many have asked me why this is – here’s a quick explanation…

CFE400M digitally-controlled medical power supply

The CFE400M, which is suitable for Type B applications, is a convection cooled power supply housed in a U chassis – which is used as a heatsink to help dissipate heat. It has a 300W continuous rating from 0 to 40°C, while still meeting the ErP requirements of 0.5W standby power and reaching Climate Savers Gold ranking for efficiency.

Our design team here in Ilfracombe have optimised the thermal performance of the unit further by using simple physics It is the emissivity value of the chassis that makes the difference i.e. how much heat radiation you get off the metal work… shiny aluminium has an emissivity value of about 0.1, whereas a black finish has an emissivity value of about 0.9.

Our design team calculated that a black finish achieves 4- 5degC better thermal performance than bare aluminium. So we added a black finish on the convection cooled CFE400M chassis to increase the amount of heat it could dissipate through radiation – of course, the heat dissipated by convection remains the same so in total more heat is dissipated .

This in turn improves the life of critical components within the unit and hence the reliability of the power supply – the CFE400M comes with a 5-year warranty.

As with many convection cooled power supplies, the CFE400M can alternatively be blown with customer air or purchased with a premounted fan. This increases available power to 400W at 50degC due to the improvement in thermal impedances.