I am currently running an outdoor event that uses a generator.
I haven't seen the generator up close, but it is a trailer about 7 foot
long. (How's that for specs?). I have some strange problems with the
sound including excessive EMI Hum in my mic lines and power amp output
fading in and out. When I originally told the electrician that I
required 2 circuits on the same phase, he looked at me funny and said he
could not guarantee phase. The electrician is unable to get his lights
running properly, so he may be creating problems. I am using 2 circuits
off the dimmer rack that individually check out OK (Hot, Neutral,
Ground). But when I measure Hot to Hot, I get 60 volts. Can anyone shed
some light on using generators or what I should look for?

Thanks

Joe Boerst

In article ,
Joe Boerst wrote:
I am currently running an outdoor event that uses a generator.
I haven't seen the generator up close, but it is a trailer about 7 foot
long. (How's that for specs?).

Find out what it is. Manufacturer, model number. How much current?
Who are you sharing it with?

I have some strange problems with the
sound including excessive EMI Hum in my mic lines and power amp output
fading in and out. When I originally told the electrician that I
required 2 circuits on the same phase, he looked at me funny and said he
could not guarantee phase. The electrician is unable to get his lights
running properly, so he may be creating problems. I am using 2 circuits
off the dimmer rack that individually check out OK (Hot, Neutral,
Ground).

Wait, you are sharing a power distro with the dimmer rack?
Bad, bad news.

But when I measure Hot to Hot, I get 60 volts. Can anyone shed
some light on using generators or what I should look for?

If you measure hot to hot, you should get zero volts if they are both
on the same phase, or 120V if they are on different phases of a 240V
system.

Is this a 208V three-phase system? A 120V system? Is there one ground
stake at the generator? Is the system impedance-grounded or statically
grounded?

What is this event? What is on the generator? Does the electrician know
what he is doing? Is your equipment insured?

How much current do you really need?
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Is your stuff all 120 Volts or is some 240 Volts?

Mark

On Thu, 14 Jul 2005 12:43:55 -0400, Joe Boerst
wrote:

But when I measure Hot to Hot, I get 60 volts. Can anyone shed
some light on using generators or what I should look for?
If you said 160V, I would have said yoy were looking at the stinger
lead (phase A-C or C-B) of a 3 phase, 240V, Delta wired rig (unusual
for off the shelf PORTABLE power). 120/208 is normal 3 phase portable
rigs 30KVA - Up

I agre! Light rack and audio do not belong on the same phase (IMH or
generator).
I would also run from this 'electrician' who can't tell you what phase
lead you load is connected to.
Duh! read the outlet breaker number fer cri'n out loud and count by
phase leads. 1,3,5 or 2,4,6 (or phase multiples)for A,B,C phase .
What other bozo things has he done? Like failure to attempt a phase
ballance?


, _
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org

Steve Urbach wrote:
On Thu, 14 Jul 2005 12:43:55 -0400, Joe Boerst
wrote:

But when I measure Hot to Hot, I get 60 volts. Can anyone shed
some light on using generators or what I should look for?

If you said 160V, I would have said yoy were looking at the stinger
lead (phase A-C or C-B) of a 3 phase, 240V, Delta wired rig (unusual
for off the shelf PORTABLE power). 120/208 is normal 3 phase portable
rigs 30KVA - Up

Lots of portable generators can usually be configured for delta as well
as wye... but why anybody would want to do this is beyond me, unless
it's for emergency power to an existing delta-wired install.

Then again, I have seen a lot of misconfigured generators at events.
One event that I often work used to have a 15 KVA generator for the
main stage. But somebody decided that they needed more power, so
this past year they went to a 25 KVA generator. Unfortunately, the
25 KVA generator was three-phase, and when providing power to their
split-phase distro had to be derated to 14 KVA. So they got higher
gas consumption and much higher rental costs, for less actual current
capacity.

I agre! Light rack and audio do not belong on the same phase (IMH or
generator).

That being the case, careful grounding can probably let you get away
with it. Also it helps to use high grade dimmers that don't throw
so much trash on the line. I have seen folks do it and be happy, but
it wasn't easy and it involved a lot of very good audio gear that had
excellent RF rejection.

I would also run from this 'electrician' who can't tell you what phase
lead you load is connected to.
Duh! read the outlet breaker number fer cri'n out loud and count by
phase leads. 1,3,5 or 2,4,6 (or phase multiples)for A,B,C phase .
What other bozo things has he done? Like failure to attempt a phase
ballance?

I think you have put your finger on the problem right here.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."