Article on generators in FOH, what info do you want to read?

P

Phil Graham

Honorary PhD
Mar 10, 2011
651
1
18
Atlanta, GA
Everyone,

Since power distribution is such a big topic for the industry, the FOH editors have given me a little breathing room to do a multi-part article on generators (at least 2 parts). Part one is very much in the NEC (sorry in advance for being USA centric).

So, with that in mind, what things would you like to see in a follow-on article about generators and portable power distribution that you saw in an industry trade rag?
 
Re: Article on generators in FOH, what info do you want to read?

Silas Pradetto said:
Cord gauge vs current carrying capability and derating based on number of current carrying conductors, and neutral and ground bonding.
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Silas,

Would references to the specific sections in the NEC where these details are contained be sufficient? I don't have the space, nor likely the rights, to present this directly as a table.
 
Re: Article on generators in FOH, what info do you want to read?

Phil Graham said:
Silas,

Would references to the specific sections in the NEC where these details are contained be sufficient? I don't have the space, nor likely the rights, to present this directly as a table.
Click to expand...

Think "executive summary.:." Cite the table and use ONE entry from it as an example.

Also consider temperature de-rating.
 
Re: Article on generators in FOH, what info do you want to read?

I'll contribute my little hack for estimating voltage drops in your head or with just a pocket calculator (US-centric, I know).

You only need to remember that 10 gauge (AWG) copper is approximately 1 Ohm per 1000 ft. Easy to remember -- all ones and zeros. The cross-sectional area doubles or halves every three gauge numbers, and so does the resistance, so there you go. For aluminum, add two gauge numbers and you're pretty close. Don't forget to figure both out and back (double the cable length).

This is useful for estimating loss and damping factor in speaker cables, too.

The above is true at 25 deg. C. NEC uses 75 deg. C, where the resistance is a bit higher. Connectors and circuit breakers add a bit of resistance, too.

--Frank
 
Re: Article on generators in FOH, what info do you want to read?

More general interest/safety topics:
How to read the markings on your cable, and the importance of using extra-hard service cord.

Why GFCI is (usually) a good thing and why bypassing them because of tripping is usually a bad idea.

The importance of grounding rods for generators


More advanced topics:
The various deratings and why

Why voltage drop matters

The impacts of harmonic currents on conductor sizing

The impacts of power factor on generator sizing

The impacts of load factor (generators aren't typically as "stiff" a power source as the grid)
 
Re: Article on generators in FOH, what info do you want to read?

Clarification on amplifier power requirements. Lights are relatively straightforward in the sense of the power required is the rated size of the light. Continuous power derating is the additional factor. With power amplifiers, the average draw is fraction of what is needed for peaks. Amplifiers may "coasting" for most of the time, but when transients occur, the peak power IS required.
 
Re: Article on generators in FOH, what info do you want to read?

I don't know if you're going to touch on the smaller generators, but how about checking whether it is ok to plug a UPS into a modified sine-wave generator?
It seems to be common knowledge that one shouldn't plug a UPS into another UPS so I would assume the same would follow here?

Jason
 
Re: Article on generators in FOH, what info do you want to read?

Another silly little thought on wire gauges and cross-sectional area, especially for audio people: Wire gauges are in 1/3 octave steps. The ratio of resistance between adjacent wire gauges is the same as the ratio of frequency between adjacent frequency bands on, say, a 1/3 octave graphic equalizer. So make 1kHz correspond to 10 AWG, for example. Then you can read the Ohms per 1000 ft off the front of your graphic. FWIW -F
 
Before I say what I want to hear about, what is the intended audience for this article? Is it for the small operator just starting, for slightly more experienced personnel, or for seasoned professionals?

Sent from my neural implant
 
Re: Article on generators in FOH, what info do you want to read?

Charles Harrigan said:
Before I say what I want to hear about, what is the intended audience for this article? Is it for the small operator just starting, for slightly more experienced personnel, or for seasoned professionals?

Sent from my neural implant
Click to expand...

From the most recent internal demographic survey, FOH's demographic skews older than you might think, and I suspect tends towards small time operations, or house guys at the world's myriad small live music venues. Truthfully it is hard to tell, because a common happening is the principle of a good-sized regional will have the FOH subscription, and then pass the issue on to the crew and shop guys.

I've written both basic instructional articles (e.g. cardioid step by step) and rather technical articles (e.g. all about neodymium). The "how to" articles generate me the most email after the fact, primarily "thanks for helping the little guy." From more technical articles, the most common emails I receive afterwards are from experienced veterans, or the engineers on the staff of industry companies.

For electricity, there is no real way for me to do anything but dive in with depth and faithfulness to the code. Its a topic with too much liability and safety behind it to consider any alternative.
 
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