Hi Raymond. You wrote:
<It says to comply with EMC requirements, large pieces of metal parts, i.e. heat sinks, shielded plates/covers have to be grounded. Can anyone give me some guidance to why they have to be.> You don't say what 'it' is, but you allude to the fact that most large bits of metal form part of the case of equipment, or may have mounted on it power switching devices. If it isn't grounded, it can radiate, or not screen, but there is no 'Law' or 'Standard' which states that large metal parts must be grounded, it's just that unless you do you may have a problem. Floating metalwork can often act as no screen at all, but you knew that... If you need an explanation of that effect then do please come back and I'll try and oblige. More importantly, for LVD or safety reasons, large metal parts should be grounded. Chris Dupres Surrey, UK.
