[amluto]

My theater knowledge is dated, but there’s a major potential benefit for LED in theater: they can modulate quickly.

I’m familiar with two kinds of high-power theatrical lighting: tungsten and discharge. Tungsten is inefficient and has poor power factor when dimmed. Discharge lamps can’t cycle quickly, so, as a practical matter, they are turned in well before a show starts (to make sure they all work!) and stay on, at full power, until after the show. A motorized shutter modulates the light output. This wasted tons of power when the shutter is closed.

LEDs can cycle essentially arbitrarily quickly, and a good driver gets a power factor near 1.

I think it would be interesting to design a theater lighting system with a DC bus. Tungsten lights (where needed) would be driven by PWM, and LEDs would be driven directly by PWM if the voltages matched or with a DC-DC converter otherwise. There would be a battery to even out the load to minimize demand charges.

I don’t know what a three-phase AC-to-DC converter rated for, say, 100kW would cost. You’d want one that can be controlled such that it can share load in a controlled manner with a battery on the DC side.

[detaro]

What benefit does a DC bus have over decentralized AC-DC converters? You'd still need fairly high voltages to keep current manageable, and high-voltage DC has its own set of "fun" challenges.

[amluto]

I haven’t made any effort to analyze this for real, but:

A circuit to drive a tungsten lamp at variable brightness off AC is cheap (a TRIAC and its driver) but has crap power factor. I imagine a MOSFET to drive the exact same tungsten lamp from DC at a few hundred Hz PWM would be almost as cheap and could be filtered to have a clean input waveform. (Or it could be driven above 20kHz to eliminate the annoying audible buzz that tungsten lamps make.)

A big LED driver (AC to DC, constant current or constant voltage plus some dimming mechanism) is not particularly cheap, and the nice ones are largeish. A pure 24V “dimmer” (12-48V in, same voltage out, adjustable PWM frequency, and DMX controls) can be had quite cheaply with excellent performance. A constant current driver would be more expensive, but a DC-input driver ought to be smaller and less expensive than a comparable AC-input driver, especially if you care about power factor and inrush current.

(Common commercial AC-input LED drivers often have godawful inrush current, because they have big filter caps to get good performance, and they don’t spend the extra money on fancy circuitry to limit the inrush current. This means that you can’t actually put 20A of driver on a 20A breaker because the inrush current will trip the breaker. With DC input, a much smaller filter cap should give comparable performance.)

Anyway, this is all mostly speculation, and economies of scale matter. But those DC DMX dimmers really do exist.)

[htkjreou]

If by theater you mean cinema, I'm pretty sure state of the art lighting is using lasers. Centralized laser in fact, where a single laser drives many projection rooms through fiber optics.

[amluto]

By theater I mean people doing things on a stage with stage lighting.