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Author Topic: Company switches and total current draw  (Read 9844 times)

Tim McCulloch

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Re: Company switches and total current draw
« Reply #30 on: October 08, 2014, 03:41:27 PM »

Yikes! That's some serious suck.... I know whole towns that use less than that.....
I'm guessing that they use a combination of venue and genny, or would they simply go all genny ?
I really can't think of any place around here with that kind of supply.

I did some re-thinking and their old PAR can rig was probably 1600-2000 amperes.  It's gone down since 7 years ago as they used more movers to replace single color fixtures, and more recently going to LEDs and video-based lighting fx.  They still do some impressive pyro, too.  Their lighting load is about 60% of what it used to be.

Seven years ago at our county's old arena, it was a combination of gennies and venue power.  At our new arena downtown, we have 2400 amperes of service split between SR and SL, with another 400 ampere service in a back-house left vom and another 400 from the catwalk.  They also have 3 200 amp services and 2 400 amp services for TV production and satellite trucks on the south west side of the venue.
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Guy Holt

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Re: Company switches and total current draw
« Reply #31 on: October 08, 2014, 07:13:41 PM »

The main issue is heating-its not like 600 amp cables are going to melt if you draw 650-or even 800 amps on them.  Even if you need the full 800 capacity for a show-what percentage of the time will the draw actually exceed 600-and for how long?  That is what will determine the heating of the cable and the ultimate degradation of the insulation.

Make sure your engineers are factoring in heating caused by harmonics.  In my experience, engineers don't have a good understanding of the type of loads that we put on a service and the potential for additive triplen harmonics that can overload neutral conductors. Make sure they are oversizing the neutrals by a factor of at least 1.5:1.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com
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Jonathan Johnson

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Re: Company switches and total current draw
« Reply #32 on: October 10, 2014, 01:36:31 PM »

If there are multiple venues - how likely are they to be active at one time?  Likely above your level of consultation, but with this distance if distribution I would consider something similar to one of our local college campus...  2400v loops that each building/venue taps off of with their own pad transformer. Lower cost wire with higher voltage. Yeah you pay for the xformer... But a ring type system rather than what sounds like a star based system would make sense to me...

Seems to me this would make more sense. Not sure what it costs to lay a set of 3-phase primaries and set a transformer, but you'll only need one set, not two. 800A at 208V is equivalent to about 70A at 2400V... that makes for a much smaller, less expensive wire. You'll also experience less voltage drop at the switch, and you'll simplify future expansion.
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Re: Company switches and total current draw
« Reply #32 on: October 10, 2014, 01:36:31 PM »


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