Power: One or Two Phases?

[Calvinv]

Hi
I run a Sound and Lighting setup for Conferences.
Typical Setup:
4 JBL 515xt (450W each, upto 900W according to the manual)
1 Audio Mixer (40W)
About 6 wireless microphones
Kramer (VGA seamless Switcher)
2 Projectors (5000L)

8 LED Lights or Parcans with Dimmer/Lighting Board (So differing power draw)

Question: What do I need to do to ensure that any changes in Lighting does not infere with my Audio and Projection feed? (Assuming that I am not exceeding 15A on a 15A feed, and Earthing is common. 240V supply)

Case: I have had instances when dimming down the lights, I get a high Frequency disturbance through my Sound System. And/or waves of disturbance in my Projection. Similar happenings when one Particulat light is switched on or off.

I have taken to connecting all Audio and Projection and TVs to one Phase and keeping all Lighting to a different Phase.
If wrong, or there is a better way of working, do mention.
Appreciate all the help in advance
Cal.

 

[theatricalmatt]

It's not about how many phases you have, it's about separating all the wiring, so that there's no neutral or ground shared between lighting, audio and projection equipment. You don't need to put them on separate legs; you need to pull them from separate power distros, preferably from separate mains feeds into the venue.

You will probably find that you have fewer issues when using the LEDs, as they draw a constant amount of power from the mains.

 

[Calvinv]

It's not about how many phases you have, it's about separating all the wiring, so that there's no neutral or ground shared between lighting, audio and projection equipment. You don't need to put them on separate legs; you need to pull them from separate power distros, preferably from separate mains feeds into the venue.

You will probably find that you have fewer issues when using the LEDs, as they draw a constant amount of power from the mains.

Thank you
Among the reading I've been doing, the article warned against not having a common Ground.
The reasoning being this: If there is a potential difference between the Earth/Ground of Lighting vs Audio, then (as an example) a performer holding a mic, who comes in contact with the metal eclosure of the say a Parcan can still get a shock.

 

[Dionysus]

Im not particularly familiar off hand with how standard electrical services work in India, Im in canada so use the North American standards (120/220/240/347/600) at 60hz, fed from various different distribution systems. Here 240v is from two phases (each 120 to earth). I imagine as with other areas of the world 240v there is one phase only (less loss over distance that way).

Its all about the transformers and how they are fed and configured not to mention where it goes after that. I'll try and keep things rather simple.

Separating like that won't help at all (at least here) as back at the transformer feeding your 240v phases all those ugly things will cross over anyways.
Like I said not particularly familar with Indian power distribution, is your normal service two 240v phases with a neutral?
It all comes down to the entire system.

ANYWAYS... Your "uglyness" with audio and video caused by your lighting is due to how the lighting is chopping up and effecting the power as a whole especially anything using a shared neutral (that neutral will have all that on it, affecting all connected phases). Different types of dimmer work a little differently, and the cheaper ones chop op the waveform quite heavily putting that ugly "noise" into the power as a whole. Sharing the same neutral makes this problem MUCH more apparent.

How to fix this (at least a little). Separate your lighting system from a different feed from the panel (if you are using distro use a second for lighting). Also try and balance your lighting load among the phases on said lighting distro. Having a separate neutral will help a lot.

Ground, well really all the grounds in the building are connected anyhow (and connected to neutral). With good dimmers and audio gear this should not be a problem anyhow.

Quality and type of your dimmers will have a HUGE effect. "Cheaper" dimmers will cause more of this kind of issue. Same goes with things like computer power supplies. LED lights will also cause some of this depending on how they work and how they are controlled and "dimmed".

Power conditioners before all of your audio and video equipment will help drastically, if you go top notch you should be able to have a huge difference. Im not talking about simple "surge protection", but actual power conditioners that will help "smooth out" your power as it were. Note that again it's all about how you lay out the wiring, because one weak link in the system will introduce the noise.

There is good reason why it is standard practice to run all lighting off of a separate "panel" or "feed", they may be on the same electrical service but at least you are separating them from each other's EMF more and the different neutrals meet up further apart in the system.

I hope that this all makes sense, and didn't bugger anything in my modification in language to try and make it easier to explain to you.

NOTE (Edit, a reply to your post that showed up while I was typing this):
EVERYTHING in the building MUST have a common path to ground (at least here, I assume the same may be the case in India). As stated this is for safety and also to make sure that things work correctly. Earth -> Ground -> Bonding point -> "Bonded conductors" through building (commonly called grounds).

 

[Chris15]

Indian electrics were based on British Standards, I don't know how they have evolved and changed since.
But it would be a safe assumption of a 230/400 three phase distribution system as the backbone, no guarantees that all phases enter a particular set of premises...

 

[Reggie]

Dollars to donuts it's the LED light and the dimmers giving you the noise. Dimming cheap LED lights magnifies the problems inherit.