IGBT vs Sinewave

[Bryson]

So, a friend of mine is getting some new dimmers for his small theatre space. His space is super-small, so he really wants quiet filaments, if not silent. (I do lighting design in there, and the triac noise is intolerable!)

 

One of the dealers is recommending the Optio dimmers from Lightolier. They're about 25-30% cheaper than the alternatives from ETC and Strand, but he's worried that they're a bit "architectural" rather than theatre. They're IGBT rather than sinewave.

 

So, two three four questions:

 

Can someone tell me about the various pros and cons of IGBT vs Sinewave dimming?

Does anyone have specific experience of this product? Will they work well in a theatre environment?

Any other products that might tick his boxes?

 

 

Bear in mind I'm left of the pond and working with 120V....

[musht]

Takes some digging to the data sheet to see IGBT is Lightoliers take on Reverse Phase Control, wonder why they buried that then...

 

RPC really really dosn`t like inductive or capaciative loads, notice much mention of incandescent loads.

Switching inductive load off suddenly can dump power into the output device , think powering down big power amp without turning gain down.

 

Sine wave dimming can play all sorts of cool voltage limiting tricks that RPC can`t.

 

ETC bought IES of Holland for sinewave dimming technology, so technology goes back further than Lightolier would like you to believe.

 

Swisson make a sine wave dimmer.

 

http://www.swisson.com

 

and Compulite have buried on their site Compusine

 

http://www.compulite.com/index.php?page_id=60

[dbuckley]

IGBT devices still cut the waveform, though less visciously and at the other end to SCRs - ie the IGBT switches on at the zero cross, and then turns off part way through the cycle. But the cutoff is slow. The ETC inteligent dimmer bars are reputed to be good in terms of their own noise (silent) and the filament noise of the lamps they control.

 

Sinewave dimmers dont cut the waveform at all thus no sing.

[Keeper of the Keys]

Technically the sinewaves do still cut the wave, just that they do it thousands of short times (>40kHz) and then use the cut wave to produce a new 'clean' wave with a smaller amplitude as output.

 

Sinewave is a better technology than IGBT RPC, but of course if the better for you doesn't express itself enough to cover the higher price then IGBT RPC is also okay.

 

As poited out above sinewave is silent because the output wave is clean, IGBT is also quieter than any triac (800µs risetime is close to silent).

 

Another advantage of sinewave is that you don't have inrush currents because the wave isn't being turned on and off constantly this can lengthen the life of you lamps.

 

Also again as pointed out above the degree of control provided by a sinewave dimmer is far higher than what an IGBT RPC can offer.

[Tomo]

There's also a huge stack of caveats with IGBT - maximum cable length, can't drive inductive loads at all....

 

The price of a 'good' IGBT is also very similar to a Sinewave - about the only saving is the lack of choke in IGBT.

- This is the main reason ETC discontinued them. Not much point is selling a product that's only slightly better than SCR for lots more cash!

 

The only exception is when driving some dimmable ballasts or transformers, which were designed for Reverse-Phase control.

 

However, Reverse-Phase control is a little bit different to IGBT - IGBT acts very much like an audio amplifer to get extremely long fall-times (thus reducing the filament sing), while bog-standard Reverse-Phase doesn't bother and has very short fall-times to make them cheaper. (There's less heatsinking required, as most of the power dissipation in an IGBT is during the 'slow switch-off')

 

- That's probably why they advertise it as IGBT rather than Reverse-Phase, as their product is presumably a long fall-time unit, thus quieter than a straight Reverse Phase.