Thread: Off Topic-replacing Halogen with LED ,electricians???

Originally Posted by ACA7

Hi guys,
The lighting lady at Bunnings said the iron core transformers could use up to 35W just themselves to function so that seems to me that a lot my savings will be taken back by the transformer.
Thanks.

What a load of... they are feeding you! I plugged a selection of transformer based power supplies into my power meter and get a reading of around 4-5 watts for a 4 amp DC supply. My biggest transformer is a 26.6 amp 320W 12V AC halogen transformer and it draws a measly 8 watts at idle. 35 watts would crinkle the paint off a little transformer in no time. 2-3 watts as I said earlier is more realistic for a 60W AC lighting transformer.

PS my desktop computer plugged into the power meter draws 156 watts. Makes lighting transformers look very good...

Try putting a 35W light globe in a small tin box and see how hot that is, the transformer would hardly get up 10 deg C without a load on.

PPS my power meter reads my desk lamp correctly so it's not wildly out either.

Originally Posted by isuzurover

She's not that far off. Everyone seems to have missed the file I uploaded on the previous page, so here it is again.

Your PDF is quite correct for a fully loaded transformer, yes I did see it. However this consumption consists of two components, namely the zero-output-current loss (which I measured directly) and the resistive loss under load. It will be approximately linear with increasing load until you get closer to magnetic saturation in the transformer cores, ie overload.

The point to be made is that a 3W-10W LED will cause much less transformer loss than a 50W halogen. It will be closer to the unloaded loss than the full load loss. To settle the question accurately you need to plug the led/s and transformer into the power meter, then work out whether the loss is greater for many low load trannies or one fully loaded. I would be surprised if there was a huge difference. If I had a bunch of these I would do it myself but I only have a couple of the monster ones.