Newsgroups: sci.electronics.basics,sci.electronics.design,sci.electronics.misc,alt.engineering.electrical
Subject: Re: Low Voltage Lighting
References: <[email protected]>  
"Romy Singh"  writes:

> --Snip--
> 
> > No problems running LV halogens at levels down to 20% or so as long as you
> > occaisionally run them at 100% to 'clean up' the deposited tungsten from
> the
> > capsule wall.
> > I use inductive rated dimmers with wirewound transformers throught out my
> > house with LV with no lamplife issues at all. In fact I think that
> lamplife
> > has actually been improved.
> > You can bounce queries like this on sci.engr.lighting NG.
> > regards,
> > JB
> >
> >
> 
> So what is the difference between a regular incandescent dimmer and a
> magnetic (or electronic) LV dimmer?
> At one time I had heard that the inc. dimmers put out a small DC offset
> which would than be fed to the transformer in the light fixture. Is that
> really the case, and is it really that bad? (bad, but how bad?)

A simple a regular incandescent dimmer when connected to highly 
inductive loads can have two side-effects:
1. The dimmer might not be too accurate on the accuracy of the 
   dimming agle both half half cycles of mains power. This can cause 
   some DC component to be generated ot the output power. This 
   DC component will heat up tranformer and can even cause 
   it to saturate (saturation leads to lots of heating and  
   can cause transformer failure).
2. The dimmer might not triger the controlling triacs always 
   reliably with highly inductive load. This can cause that 
   on soem dimmer settings the light could be unusable, 
   can flicker etc. 



-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/