More Phase Questions

[starksk]

Okay so I wanna ask some questions with pictures

So power comes out a disconnect and into something like this right?

From there, the Camlocks daisy chain off to a dimmer rack correct? And then if there are two dimmer racks can the cam locks daisy chain off one rack into the other?

In the picture above theres a row of plus and it has A plug coming out but only one, and I have no idea where it goes. And the top row has one plug comming out, but once again I have no idea where it goes or what its for.

Then the two rows go out and connect to the sound equipment like this right?

What kind of cables are those?
Or the other two that I dont know what they're for?

First of all, these pictures all look like sound equipment and power distribution.

While it is possible that the distro pictured in the top picture is also daisy-chained to the lighting rig, it is unlikely as sound guys don't like the noise that lighting can create on the line.

The top rows are edison power that sound guys use to power accessories that need to share the same ground (for noise reduction purposes). The second row that has the single connector attached looks to be a powercon connector that is used to power some powered speakers.

The third and fourth rows look like they are twist-lock connectors, possibly running to the amp and equipment racks that are pictured in the second picture but looking at the the gender, they are either reversed, or drawing power not providing power... I will leave that to the sound boys (and girls) to answer.

The next row looks like those used by snakes that run to consoles, but again I have been away from the sound side of the industry for too long to remember exactly what use those connections serve.

Finally at the bottom are the Cams that provide and also appear to be passing the feed power through the rack. Those are the things that are the most similar to a lighting touring rack. The cable that feed those connections are usually called feeder and are quite thick to be rated for the appropriate feed and amperage needed for the equipment.

_____________

~Kirk

 

[Shawncfer]

What does power supply for moving lights look like? Like does anyone have any pictures?

And does power go to a distro, and cam locks daisy chain to a rack, and then the different cables go out to power intels, LEDs, rotators, scrollers, and all that other shinanigans?

 

[epimetheus]

The third and fourth rows look like they are twist-lock connectors, possibly running to the amp and equipment racks that are pictured in the second picture but looking at the the gender, they are either reversed, or drawing power not providing power... I will leave that to the sound boys (and girls) to answer.

The next row looks like those used by snakes that run to consoles, but again I have been away from the sound side of the industry for too long to remember exactly what use those connections serve.

The third and fourth rows look like 20A or 30A twist locks that probably provide power to powered speakers or perhaps amp racks. The panel mount connectors do seem to be the wrong gender though for power outlets (the panel mounts look like males, which are generally power inputs). The fifth row looks like 50A connectors which would be most likely be power feeds for amp racks, though it's hard to determine what gender they are from the pictures.

 

[epimetheus]

Shawncfer, I dig the fact that you're asking these questions! There was a time when I was asking these questions myself; I decided I liked the answers so much that I decided to get an electrical engineering degree!

 

[jstroming]

I always hit this one convention center in the northwest that the house electrician WON'T tie in tails for you. Take a guess what that disconnect looks like after 5 years of random dudes tieing things in HAHA.

I agree with epimethius above, and am thankful the rules were changed so things like this can be addressed. Years ago (and still!) I would ask a shade-ster old roadie friend of mine, and god only knows how accurate that would be! This opens things up a bit. Happy their seems to be a common ground here where some of these topics can be addressed safely.

 

[JD]

Most sound companies that I have known and worked with like to have everything separate; Distros, feeders, and even a separate company switch if possible!

Outside of sine-wave dimmers, current lighting equipment is brutal on the waveform! Don't blame them myself.

 

[Shawncfer]

So can power go to a distro and then daisy chain to a dimmer rack and then daisy chain to another rack??? And does power go from the distro to power multi paramater fixtures? Or what does it power?

 

[cdcarter]

So can power go to a distro and then daisy chain to a dimmer rack and then daisy chain to another rack??? And does power go from the distro to power multi paramater fixtures? Or what does it power?

Yes, though a distro isn't always needed/used. The distro rack that is included can power anything. Usually this means your movers, but in some cases it can be your electricians phone charger (if an extra 120V circuit is open).

The distro can usually supply both 120V (phase-neutral) power and 208V (phase-phase) power, but that depends on who made it, and what purpose it is being used for. A rental house near me has one distro that only has 9 208V circuits on it, is mounted to an old wooden board, and had cobwebs on it one time I used it.

 

[derekleffew]

What does power supply for moving lights look like? Like does anyone have any pictures? ...

Here's three:

DL's Photobucket
On these models, the main circuit breaker, Cam-Lok inputs, and pass-thrus are on the back; and the branch circuit breakers, 120V convenience outlets, and 208V Socapex outputs are on the front.

Motion Labs - Power distribution and motor control systems

Motion Labs, Lex Products, and Entertainment Power Systems, are three of many manufacturers of touring distros.

 

[Shawncfer]

So Derek,

do the passthroughs go straight into the dimmer rack? Or can they atleast? And if so, how do you know you have enough power for the dimmer rack?

Second. I know we use Socapex to run from dimmers to conventionals more for touring groups and stuff like that. But does power run from the distro to the moving lights through socapex as well? And, I've worked with some moving lights before, but do more expensive intels, (Martins, High ends, etc.) have edison outlets or are they just daisy chained for power. And if so, with what kind of cable are they daisy chained?

Third. In your picture, there are three types of cables I see. In the bottom right are camlocks, the green, blue, white, and red cables. Right? What kind of cables are those really thick ones on the left side and what do they usually power? And then what are those really skinny ones in the middle conencted to the little boxes, and what do they usually power?

Derek, I know I'm probably annoying you with so many questions. But I really appreciate the help all of yall give!

 

[mstaylor]

So Derek,

do the passthroughs go straight into the dimmer rack? Or can they atleast? And if so, how do you know you have enough power for the dimmer rack?

Second. I know we use Socapex to run from dimmers to conventionals more for touring groups and stuff like that. But does power run from the distro to the moving lights through socapex as well? And, I've worked with some moving lights before, but do more expensive intels, (Martins, High ends, etc.) have edison outlets or are they just daisy chained for power. And if so, with what kind of cable are they daisy chained?

Third. In your picture, there are three types of cables I see. In the bottom right are camlocks, the green, blue, white, and red cables. Right? What kind of cables are those really thick ones on the left side and what do they usually power? And then what are those really skinny ones in the middle conencted to the little boxes, and what do they usually power?

Derek, I know I'm probably annoying you with so many questions. But I really appreciate the help all of yall give!

I am just catching up on this thread so I will multible responces. As far as doing tie-ins, even if you carry an electrical certification or even a license, most houses won't let you tie in yourself. As one that aps shows all the time, I require the show guy to come check it before I hot it. Many guys will say it's OK they have meters on their gear, I still insist they look first.
How the power gets in your system is really a by-product of how your company set it up. Many times there is a distro that feeds power to various pieces of equipment. Other times it will go straight to the rack. Some dimmer racks have passthroughs to pass power along.
What do distros look like is kinda like what do cars look like. There many flavors and depends on use and size of show. Some are small and are simply a distro to break up the power in different directions. Others have mover power on it also. Some have motor controls tied in with but that is rare. I did a show with rental gear and the motor distro was on one side and mover power on the other. Mover power can be sent through Soca but the power end has to go to straight power not a dimmer. Once on the truss most will use a Soca to edison breakout.

 

[derekleffew]

... do the passthroughs go straight into the dimmer rack? Or can they atleast? And if so, how do you know you have enough power for the dimmer rack? ...

Power may by daisy-chained using a rack's (dimmer or ML PD) pass-thrus in any order, but most put the rack with the largest load first in the chain. As for "how do you know you have enough power for the dimmer rack?", the master electrician does a load calculation. See Power for rig, Power for rig2, for examples.

... Second. I know we use Socapex to run from dimmers to conventionals more for touring groups and stuff like that. But does power run from the distro to the moving lights through socapex as well? And, I've worked with some moving lights before, but do more expensive intels, (Martins, High ends, etc.) have edison outlets or are they just daisy chained for power. And if so, with what kind of cable are they daisy chained? ...

Larger moving lights are normally run at 208V. Socapex is plugged into a 208V distro and an L6-20 breakout is used on the truss. One never daisy chains power at the fixture (except for some LED units).

... Third. In your picture, there are three types of cables I see. In the bottom right are camlocks, the green, blue, white, and red cables. Right? What kind of cables are those really thick ones on the left side and what do they usually power? And then what are those really skinny ones in the middle conencted to the little boxes, and what do they usually power? ...

In the picture, the 8 cables on the left vertically are the 208V Socapex for moving lights, VL3000s, IIRC.
The thin cables in the middle are all DMX cables plugged into to opto-splitters.
The ones in the lower right are Cam-Lok 4/0 feeder.

 

[JChenault]

There are effectively three dimming engines in a three-phase control module, each synced to the zero-crossing point of the three phases. Dimmers on each phase must be "told" which dimming engine to operate from. That's the 3-phase/single-phase setup in a CEM.


ST

Steve

I'm trying to build a mental model of how this works, and what a dimming engine does. ( The last time I really studied a dimmer wiring diagram was about 40 years ago looking at a Kliegl wiring diagram).

I think that what you are saying is that the DMX signal comes to the CEM. The CEM decides when to send the 'Switch On' signal a dimmer based on it's understanding of what phase the dimmer is getting, and where the crossing point is. IE based on the DMX value it will wait X microseconds after the crossing point to tell the dimmer to turn on. This implies that the dimmer modules are pretty simple, and the interesting logic is in the CEM.


From a high level is this how it works or am I missing something.

Thanks

 

[JD]

IE based on the DMX value it will wait X microseconds after the crossing point to tell the dimmer to turn on. This implies that the dimmer modules are pretty simple, and the interesting logic is in the CEM.

Pretty darn close! As the waveform crosses the 0 volt point, the ZVD produces a logic pulse and the CEM starts counting. It is the CEM that calculates how to translate various dimmer curves. The CEM outputs a firing signal which goes through an opto-isolator to turn on the SSR, so yes, there is not much going on in the power module outside of filtering and protection.

As Steve said, there are three ZVD circuits, one for each phase leg. The CEM also takes care of mapping which ZVD pulse should be used on which virtual dimmer counter. Everything between the ZVD pulse and the firing pulse is more or less software programed into the CEM.

In the case of ETC, line voltage is also inputed as data to the CEM so that pulse timing can be altered to compensate for fluctuation in the line voltage and keep the output at the same level.

 

[Shawncfer]

Okay,another question. So when a dimmer rack is hooked up to three phase, its set up so that 1/3 of the rack is able to run on one phase, another 1/3 one the second phase, and the last third on the third phase. Now I get that and that makes sense. And I also know thats possible because of the ground. Now, I just dont get that concept. Like I know it does it, I just dont know why. And also, do you have to have three different grounds? I mean I know you don't, but I dont see why not. Hope someone can help...

 

[MNicolai]

The transformers have three phases outputting on them. The neutral picks up any imbalances between the phases. If all are loaded equally, no current is driven into the neutral. The more the phases are out of balance, the more current ends up on the neutral. The more out of balance a transformer is, the less efficiently it operates; it takes more power in to transform less power out.

Transformers for dimming systems are built and designed to handle a large imbalance given that's the nature of entertainment lighting. We have no idea in a given preset if the loads will be distributed evenly or if all lights will end up on a single leg.

You do not have to have three separate grounds, just as you do not need three separate neutrals. I'll defer further discussion on grounding to someone far more knowledgeable on the matter.

 

[JChenault]

Okay,another question. So when a dimmer rack is hooked up to three phase, its set up so that 1/3 of the rack is able to run on one phase, another 1/3 one the second phase, and the last third on the third phase. Now I get that and that makes sense. And I also know thats possible because of the ground. Now, I just dont get that concept. Like I know it does it, I just dont know why. And also, do you have to have three different grounds? I mean I know you don't, but I dont see why not. Hope someone can help...

I think there is a confusion here about neutral -vs- ground they are not the same thing.

While there are others on this group more able to define this, I will take a shot at it.

When you are powering any electrical device, the electrons need a complete path. In an AC system ( What is in common use today) you have the hot leg and the neutral leg. In a stage pin plug, these are the outside pins. In an edison plug they are the blades. The neutral leg is intended to be the return leg for the electricity back to the generator that produced the power. The neutral leg is designed to have electrons moving along it all the time.

The ground leg, on the other hand, is a safety device. It connects the case of the device ( say your leko) to the ground. The idea is that if your wiring in the fixture becomes frayed, and the hot wire touches the case, the electrons will travel down that wire instead of through you when you touch the fixture. The ground is not intended to carry current unless there is a problem. This is the reason that the ground pin on a stage plug, or the ground plug on an edison is just a bit longer than the hot and neutral. It will connect first so if there is a problem with the fixture it will be grounded before it is powered.

Let's look at a simplified example. Consider a dimmer rack that has three 20 amp dimmers, and is powered by three phase power. There are four wires coming into the rack. Phase A, Phase B, Phase C, Neutral, and Ground. If I put dimmer A up full, I will see 20 amps moving through Phase A, and 20 amps through Neutral, and 0 amps on Ground. If I power up dimmers A, B, and C to 20 amps each, I will see 20 amps moving through each of the phases, 0 amps through neutral, and 0 amps through ground.

(Ok - the above is not completely accurate as the SCR dimmer adds some inductive load which is part of the reason the neutral needs to be oversized )

 

[Shawncfer]

If I power up dimmers A, B, and C to 20 amps each, I will see 20 amps moving through each of the phases, 0 amps through neutral, and 0 amps through ground.

(Ok - the above is not completely accurate as the SCR dimmer adds some inductive load which is part of the reason the neutral needs to be oversized )

Thank you first of all.

Second, How come when all three are on theres no power in the nuetral?

Third, how is the nuetral oversized. THATS what through me off. I read in the book, "Electricity for the Entertainment Electrician and Technician" that the nuetral needs to be over sized but I didn't understand why?

 

[sstolnack]

I think there's no power in neutral because if all 3 are at equal power, they cancel eachother out because they are shifted 120', right?

 

[JChenault]

Thank you first of all.

Second, How come when all three are on theres no power in the nuetral?

Third, how is the nuetral oversized. THATS what through me off. I read in the book, "Electricity for the Entertainment Electrician and Technician" that the nuetral needs to be over sized but I didn't understand why?

Let me try to explain it

Let's start by thinking about the electron flow alternating current. In DC the electrons flow from '-' to '+'. IE if you have a flashlight powered by a battery, the electrons are moving from the '-' terminal of the battery to the '+' terminal. The electrons move in one direction only. With AC things get a bit more interesting. In AC power the direction of the electrons alternates. The electrons flow in a sine wave similar to this. http://www.controlbooth.com/forums/glossary-m-s/12227-sine-wave.html So if you have a single light which is being driven by AC power, and you look at the electrons moving in the hot leg, you will see them moving one way, reversing, and moving the other way 60 times a second. If you look at the neutral leg, you will see the same thing. IE moving back and forth 60 times a second.

For the sake of this discussion, let's call the direction of the electron flow positive if it is above the center of the graph, and negative if it is below the center of the graph. The number of electrons moving is proportional to the distance from the center of the graph.

For simplicity sake, let's consider a single phase, three wire system. (The example is easier to follow and the same underlying principals apply to three phase). In this system you have a single neutral, and two hot legs - and each hot leg is 180 degrees out of phase with the other. IE when the electrons on phase A are moving positive, the same number of electrons are moving negatively on phase B. Another way to think of this is to draw another sine wave moving in the opposite direction to the first.

BeanAnimal's Bar and Grill - Electricity and the Aquarium

There are 120 volts between phase A and neutral, and 120 volts between phase B and neutral. (And 240 volts between Phase A and Phase B - but we don't care about that now)

Let's hook up a light to phase A that takes 1000 electrons to power it up. (It's a thought experiment ). This means that the number of electrons moving through the wire will vary from 0 to +1000 to 0 to -1000 and repeat 60 times a second. If we look at the neutral wire we will see the same number of electrons passing through it.

Now lets hook up a another light of the same power to phase B.
From phase A we are sending to the neutral. 0 +1000 0 -1000 0 ..
From phase B we are sending to the neutral. 0 -1000 0 +1000 0 ...

So if we look at the electrons at any point passing through the neutral wire, we see that they cancel out and there are no electrons going through the wire as long as the two circuits are identically loaded.

Now three phase uses the same concept, except the picture is harder to draw and wrap your head around. IE when phase A is at +1000, phase B+C together make -1000 but it is not as intuitive.

Basic Electricity

The neutral needs to be oversized because dimmers are an inductive load. What that means is the the dimmers can 'Shift' the time of the returning electrons a bit. ( This is one of the things the choke does in a dimmer - also the filament in the lamp ). So it is possible in a system with inductive load to have more electrons going through the neutral than a single phase. We handle this by oversizing - IE we put in a wire which is physically bigger and can handle more electrons without heating up for the neutral wire.

Good questions - hope that helps. If someone who really understands this stuff better than I do has a correction please feel free to clarify.