It is most likely a stressed component overheating internally and shutting down. If an SMPS design for a steady resistive load ( halogen lamp ) then when it is loaded with a non resistive load that varies rapidly its internal protection devices may decide to shut the device down.
I cannot understand why the original installation utilised Electronic transformers for incandescent lights, I would have thought is more cost effective just to have a simple 240/12v transformer with overload protection.
A poor quality SMPS can be made cheaper than a wound transformer. An SMPS can provide a stable and accurate voltage for the lamp even if the input voltage varies. This prolongs the life of a halogen lamp.
Thanks for our your response Bernard, it has helped me enormously.
The stressed component suggestion is possible but I have two Transformers exhibiting the same characteristic, maybe the same component is being stressed, but probably unlikely.
The price of SMPS is surprising that they will probably be cheaper than the old wound transformer thing but on reflection very probably as a wound transformer set up would also require some form of protection increasing the unit cost, so your suggestion is almost certainly correct.
Thanks again for your very helpful feedback, it is more appreciated than you probably realise, Thanks again.
Thanks again Bernard.
I always knew Electrical Power Engineering was the easy option to Electronics, clearly that is why I opted to Electrical Machines as a Major, I was not clever enough for the latter. !!!!!!!!!