transformer blows, why?

[dimmer]

what could be the possible reasons why a transformer blows.

changed a ELV down light transformer (one per fitting)

when switched it on it worked for 2 seconds then the transformer popped.
wired correctly mains to primary, lamp to secondary.
out of 5 lights only one works all the transformers have failed over time
No insulation over them , seem to be installed correctly

 

[securespark]

Buy Osram Holtronic transformers then see if they blow.

First, check the incoming voltage.

216-252V ??

 

[333rocky333]

Buy Osram Holtronic

Or even HALOTRONIC