Control/Dimming balancing loads in the realworld

[sjp]

hey all, crazy question:

When in a show setting where you have the ability to manually patch circuits to dimmers and are attempting to balance feeder load correctly, rather than just looking at wattages of individual lights, and plugging in per math, does anyone look at it in terms of systems?

i.e: by the straight wattage math you've just patched your show in attempt to balance loads, only to discover you've just patched all the backlight systems together on the same leg. (a system with lights most likely to come on at full wattage the same time for longer periods)

i only ask cuz i'm in control of a dimming system that is basically a hodge-podge of single phase 12pack dimmers where the main 3 phase feeder legs are teed-off all to hell to power them. Patching for balanced loads is a nightmare where normally i'm dealing with full 3phase racks and have to think a little less to be balanced.

I guess i'm just wondering how others approach balancing loads in actual practice....

 

[lukejoyner]

My general theory to balancing loads is to group the fixtures, not by power, but more by how they will be used.

For example, in my situation, While the Back light for the stage is split up on 3 circuits, they will generally be on together. I split these across the 3 phases. Same for my Par circuits.

It is generally pretty easy to patch a dimmer at the console.

To me, it doesn't matter if you are using a 3ph dimmer (or distro), or a heap of 1ph dimmers fed from seperate phases. Balancing phases will only make your job easier in the long run.

For example, I was doing support for an outdoor festival, stage running off gensets, where every time the LD hit the blinders during programming, the extra load was that far out of balance that not only would it cause a voltage drop on the other two phases, but the extra load on the generator was causing it to slow down to 39Hz (in a 50Hz system). The generator protection would then kick in and cut the generator, and in turn power to the stage.

The simple solution was to balance the blinder circuits accross the 3 phases. 10 Minutes of patching later, and the problem was fixed.

My own shows now, I take particular care to balance my loads as per how theywill be used, rather on pure wattage alone.

my 2c, YMMV

 

[Chris15]

Go run a search, we've been over the need to balance your loads many a time before...

The crux is that for a mains feed, the need is negligible, for generators it's worth doing to an extent...

What will cause a gennie to complain is a lack of constant load. What's happenins when the blinders get hit is more a product of the generator than the phase balance. The changed load changes the back EMF on the generator coils. Physics intervenes and the generator gets unhappy.

I have seen a 200kVA generator where the exhaust was bouncing in time with the music and blinders...