Wierd one....

Earthing the ceiling grid will not do the lights any harm. The LN reversal is interesting, of course no CE marked fitting should care about LN reversal , as  neutral insulation has to be to the same standard as live, but I agree it feels very wrong.

It may be a clue and mean that internally the mains is single phase rectified (one diode in series with one line rather than a bridge of 4 diodes which would treat L and N equally.) It also suggests that the internal high frequency filtering of the rectified mains before it goes into the switch mode supply part is pretty poor in these units.


One of the stranger effects of cheap semiconductors in this century is that it is now worthwhile to rectify the 50Hz mains to a DC and then chop it up again to make a really rough alternating current at a much higher frequency (typically supersonic, anything 20 kHz upwards to perhaps half a MHz or so) so a far smaller and lighter (and so cheaper) transformer can be used than would be needed at 50Hz. The hidden problem is that such things tend to be designed and built by folk who cut their professional teeth on 50Hz  power engineering and laminated iron cored transformers years ago, rather than specialists in what it has become, which is more of a branch of high power Radio Frequency design, and accidental RF emissions, both radiated, (have you tried to find a quite spot on a MW radio recently ?) and like this, conducted, are the result. The product standards and recommended test methods are always playing catch-up to an extent as the practice keeps evolving.

Earthing the ceiling grid will not do the lights any harm. The LN reversal is interesting, of course no CE marked fitting should care about LN reversal , as  neutral insulation has to be to the same standard as live, but I agree it feels very wrong.

It may be a clue and mean that internally the mains is single phase rectified (one diode in series with one line rather than a bridge of 4 diodes which would treat L and N equally.) It also suggests that the internal high frequency filtering of the rectified mains before it goes into the switch mode supply part is pretty poor in these units.


One of the stranger effects of cheap semiconductors in this century is that it is now worthwhile to rectify the 50Hz mains to a DC and then chop it up again to make a really rough alternating current at a much higher frequency (typically supersonic, anything 20 kHz upwards to perhaps half a MHz or so) so a far smaller and lighter (and so cheaper) transformer can be used than would be needed at 50Hz. The hidden problem is that such things tend to be designed and built by folk who cut their professional teeth on 50Hz  power engineering and laminated iron cored transformers years ago, rather than specialists in what it has become, which is more of a branch of high power Radio Frequency design, and accidental RF emissions, both radiated, (have you tried to find a quite spot on a MW radio recently ?) and like this, conducted, are the result. The product standards and recommended test methods are always playing catch-up to an extent as the practice keeps evolving.