i have a moderate understanding of how power distribution works on hollywood sets for running continuous lighting etc. but i am interested in the technical side of it, ie what is happening inside distribution boxes in laymen's terms. i have been reading up on distribution, but have never practiced it, im just fascinated by electricity.
i understand they use 3 phase power from a generator or wall connection, usually 5 wires, 1 per phase and a neutral and ground.
so, 3 phases can be split multidirections, ie the main service line comes into a distro box (box 1) that in turns sends power to 3 other distro boxes (box 1a, 1b, 1c), i assume one hot leg from distro box 1 to distro boxes 1a 1b and 1c ...?
and the ground and neutral wires just connect up in the first distro box (box 1)? this would provide 1 phase power to each 1a 1b and 1c distro boxes...? if you had 300 amps coming into distro box 1, and split each hot leg to a separate distro box, then you have 100 amps for each distro box 1a 1b and 1c...? correct?
also... 3 phase is needed for running a high wattage light, 5k or bigger...? from what i understand even these lights are 120v. so to run one of these lights do you use a distro box that ties all the phases together into one hot to run the light in additional to the neutral and ground of course...?
so, 3 phases can be split multidirections, ie the main service line comes into a distro box (box 1) that in turns sends power to 3 other distro boxes (box 1a, 1b, 1c), i assume one hot leg from distro box 1 to distro boxes 1a 1b and 1c ...?
also... 3 phase is needed for running a high wattage light, 5k or bigger...? from what i understand even these lights are 120v. so to run one of these lights do you use a distro box that ties all the phases together into one hot to run the light in additional to the neutral and ground of course...?
I assume that 'tie together' was a misstatement. That would make some great fireworks.
3 phase is where I call an electrician. I've wired a few 3 phase things, as long as there's a clear diagram but it's past my comfort zone.
One last thought. Even some licenced electricians do not know 3 phase very well since you'd never see it in residential use. Be careful.
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
also... 3 phase is needed for running a high wattage light, 5k or bigger...? from what i understand even these lights are 120v. so to run one of these lights do you use a distro box that ties all the phases together into one hot to run the light in additional to the neutral and ground of course...?
thanks.
A light bulb by it's nature will only ever be single phase. They can be 120v or 240v but usually will not come in higher voltages.
You can subfeed another panel either single phase or 3 phase from a 3 phase panel or you can take either 3 phase or single phase circuits from a 3ph panel. So a light fixture can be fed from a single or 3phase panel but with a single phase feed.
Equipment that is wired 3 phase is usually mechanical, motors, tansformers, or heating. Doug is correct that 3 phase is used to keep wire size down and keep the amperage lower. You will never see anything at 120v 3phase. Always 208 or 480 or 600v for 3phase.
Cheers
Chris
__________________ "Never Stop Learning"
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White Balance so easy, even our 5 year old can do it.- Melissa Strickland
so what do the big lights have a voltage converter in them or something...
if the three phases are 208 280 and 600v, and the bulb is spec'd to 120v, and no more than 1 of those phases is going to a light, how does that work..?
part b. to go above 10kw, is 240/230v required or can it be done in the US with just a bigger service?
What type of lights are these? I doubt if anyone makes a 10Kw incandescent light. If these are vapor (mercury, sodium etc) then they will run a transformer with the light and these could be 3 phase. I am not sure what voltages are ran in 3 phase but the example above would be 3 separate setups, for example in the 208V it would be 208v between any of the phases and if memory serves correctly it would be 120v from any phase to ground.
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
so what do the big lights have a voltage converter in them or something...
if the three phases are 208 280 and 600v, and the bulb is spec'd to 120v, and no more than 1 of those phases is going to a light, how does that work..?
part b. to go above 10kw, is 240/230v required or can it be done in the US with just a bigger service?
Sorry Michael - I wasn't more clear. Single phase is a combination of the two voltages. 120 and 240v. You measure from hot wire to hot wire and get 240v. You measure from hot to neutral and get 120v. So you have one 240v circuit or 2 120v circuits.
Incandescent lighting is only ever single phase. The bulbs are built to work with either 120v or 240 volt. I would imagine that 5000 watt bulbs are very specialized and would be only 240v.
For part B what do you mean by going over 10KW? I'm pretty sure you won't get one light that is 10KW? That would draw over 40 amps at 240v. Or are you referring to a bunch of lights adding up to 10KW?
__________________ "Never Stop Learning"
All Nikon Digital www.photos-now.ca
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
Electrical work on movie sets is highly specialized work. Most lighting is done with what's called HMI lighting, which is a type of florescent light that needs a separate ballast to operate. They run any where from 2k to 18k and above. If you're wondering what 'k' stands for, it's Kilo Watts. So that means that an 18k light is equal to 180 100 watt light bulbs. When you see a row of parked movie trailers (a 'circus' in the lingo), at least one of those trailers is the generator to run the lighting.
The other thing that's highly technical is that the speed in which the HMI flickers (like a florescent, it's not constant) has to be in phase with the cameras, or there will be a flicker on the film that you can't see while filming. That happened once on a film set I was working on (luckily before I arrived) when they cheaped out on the electrician, and they lost an entire day of filming.
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