why did my transformers fail?

[fallingditch]

Just moved into a new house. In the kitchen there were 9 x 50w 12v halogen downlighters, each individually transformed by (9) colux ET 60 20VA-60VA transformers. All 9 are wired through a single Home Automation 1000VA dimmer. So ... in the interests of economy, I replaced all 9 x 50w lamps with 9 x 20W. Imagine my surprise when after a couple of weeks, 5 of them had failed. But it wasn,t the lamp which failed - it was the transformers!! Question is, WHY DOES A REDUCTION IN LOAD CAUSE TRANSFORMERS TO FAIL ?

 

[breezer]

what is / was the minimum load for each transformer?

 

[bernardgreen]

Question is, WHY DOES A REDUCTION IN LOAD CAUSE TRANSFORMERS TO FAIL ?

Electronic "transformers" convert the right amount of power for the lamp they are designed to power. If the lamp doesn't take all that power then the power not used by the lamp has to be lost in the "transformer" which is not designed to do that so it overheats and either opens it safety cut out or one of more components are destroyed.

Transformers transform 230 to 12 volts and allow the lamps to take what ever power they need up to the maximum the transformer can supply. This is limited by the current capacity of the wire used in the coils.

Electronic "transformers" work in a totally different different way. In simple terms they take lots of little bits of power from the mains side and push them across to the output side. The size of the bits and the rate of taking them is set to give the rated ouput.

The analogy is taking cupfulls of water from a high pressure tap and pouring the water into the low pressure drain in the sink. If the water cannot drain out of the sink as fast as the cups are poured into it then it overflows.

Bernard

Sharnbrook

 

[DESL]

WHY DOES A REDUCTION IN LOAD CAUSE TRANSFORMERS TO FAIL ?

Your tranformers are running under their specified load.

20VA ~ 20Watts

You dim input side of transformer hence less power on output side and for 20W lamps the load will drop below 20VA

 

[fallingditch]

My objective in doing all this was to lessen the maximum energy output in the kitchen from 9x50=450W to 9x20=180W. Had I known that switching to lower power lamps would have caused these problems then I probably wouldn't have started, but hey ...

So given that I still want to reduce power output, I think I have 3 options:
1. Replace all 9 transformers with new transformer eg these which operates down to 0 watts, and which will still be dimmable
2. Throw transformers and fittings away; replace with 35w mains halogen downlighters (saving 15 watts each - big deal but still dimmable - probably my preferred option)
3. Throw transformers and fittings away; replace with 9w mains CFL downlighters (saving 41 watts each, but no longer dimmable)
4. Move to LED technology ... (and get chequebook out ...)

opinions? (or links to a thread where this stuff has been discussed before?
_________________________________
lynda, moderator

edited to correct link

 

[DESL]

then I probably wouldn't have started, but hey ...

We all learn from our mistakes - me I'm professor of c*ck ups!!

Option 2 will be the cheapest short term solution

Option 3 worth a look at as I did read that there are dimmable cfls on the market or coming on the market soon


There is a free option

If you use 20W lamps you can run 3 of them off each of your remaining 20-60VA trannies and you'll have a spare trannnie in case.