Dimmer with Halogens - flickering and noise

[Aragorn84]

Well surely the fact its flickering and isnt working properly means that your particular model DOESNT infact like dimmer switches?

 

[tim west]

Its more likely the fact that the dimmer isnt loaded enough, the symptoms described do point to this, it may be a case of adding another load preferably a resistive one.

With phase angle dimmers the triac has to see a sufficient holding current in order for the relevant thyristor to stay conducting for the duration of the half cycle (with inductive loads like transformers they appear as a light load)if there is'nt enough holding current the thyristor shuts off as soon as its trigger pulse disappears and doesnt again conduct until the next gating pulse.
This happens with both sides of the triac and the load flickers accordingly

 

[Steve]

The OP could try replacing the transformer with a dimmable one. They can normally be swapped these days (as opposed to when they used to form part of the structure of the fitting)

 

[Turps]

I assume that your fixture uses an electronic transformer

Dimmers come in two different types

The older leading edge dimmers often have problems with low voltage lighting as the electronic transformer make the voltage and current slip out of phase and the transformer distorts the sinusoidal wave form. Even transformers that are said to be dimmable can give rise to flicker and buzzing.

A trailing edge dimmer will work better for this application. However you should check that the transformer is not wire wound as trailing edge dimmers don't generally work for wire wound transformers. A 120W wire wound transformer would weigh in at about 1kg so this seems unlikely.

This is a good simple guide to dimmers

http://www.ilight.co.uk/downloads/iLIGHT Binder-HowDimmers.pdf