Ben Mack wrote:
Hi

I've installed some 12V halogen lights in some shelves, such that I have
to mount the transformer remotely. I used 3m of normal 1.5mm^2 lighting
cable to connect the transformer to the lights, having calculated a
300mV drop across the cable (30mV/A/m x 3.3A x 3m)

What makes you think that the lights are only taking 3.3A?


However in practise I'm losing around 6V in the cable, and have
discovered that the transformer output is 125kHz, not 50Hz, explaining
the bad attenuation in the cable


Irrelevant. That's not the problem. I don't know what is, but its not that.



So my question is - do all compact dimmable 12V transformers have high
frequency outputs?

I don't have space for an old-fashioned 50Hz transformer

Straneg..they are not much bigger than teh HF units...however for
dimmable HF is usually better.

Anyway, I did this for 3x50W units, and used similar run of 2.5mm per
lamp starred off a junction box with cooker type cable feeding it.

It's fine..
Cheers