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Author Topic: Generator and Amp protection?  (Read 11914 times)

Ivan Beaver

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Re: Generator and Amp protection?
« Reply #20 on: November 19, 2011, 10:09:03 am »

The Honda EU series generators are pretty much the only reasonable choice for a small generator for sound reinforcement, not only for the power quality issues already mentioned, but also because they are 10-20dB quieter in operation than the construction junk.
We have a 5Kw Honda that we use for moderate sized demos and field testing-where no power is available.

They are quiet-provide stable output and we have not had any issues with them.  And when pushed hard it appears as if they sag "gracefully".

Agreed-if you want ot do anythng "real", you HAVE to get a real regulated generator.  Otherwise you are just asking for trouble-which will cost much more in the end.
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Ivan Beaver
Danley Sound Labs

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Jon Geissinger

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Re: Generator and Amp protection?
« Reply #21 on: November 19, 2011, 12:20:33 pm »

Use a diesel generator.  If you are worried about sags and peaks, then put an online UPS in the middle of the power chain or a power conditioner.  ALL of that stuff is very heavy!  But, the diesel generator is less prone to sags, a UPS will pick up any sags (long term sags) or a power conditioner will handle short sags.
I UPS will clean any other power issues as well (online UPS, actually runs off the batteries all the time instead of when there is a power outage).
Don't put lights on the same circuit as the sound equipment.
Just my 2 cents.
GENERALLY SPEAKING, Watts are watts, makes NICE conversion tools.
5KW amp and you plan on using it more than , 50% of the time at full power means 5KW input to the amp.
Northern (Tool and Equipment) has a 5.5KW (surge) genset for $1099, 407 lbs, electric start, 7 hours run time at half load.  Not a bad deal.
Watch for industrial sales of welder gensets.  Those can be quickly converted to what you need and they are already on a trailer.
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Ivan Beaver

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Re: Generator and Amp protection?
« Reply #22 on: November 19, 2011, 12:58:40 pm »

  But, the diesel generator is less prone to sags, a UPS will pick up any sags (long term sags) or a power conditioner will handle short sags.
There are very few "conditioners" that will pick up "sags".  And for the size that you can run amps off of-they are going to be expensive.

Of course 5KW UPS's are not cheap-not light.

Almost all of the "conditioners" that are on the market are pretty much worthless.  A couple of MOV's hung across the line for spike protection. 

They do NOTHING for sags.  And when they blow-you have no way of knowing-so they are no longer providing any protection-even new it is a very limited protection.

For real protection- you need something like the Surge X products.  But (I could be wrong) I am not aware of the survgex providing any "pickup" for the sags.

I used a triplite unit for awhile on my FOH gear.  it was a switched transformer that would actually pick up the sags.  It worked well for awhile.  But then the switching started getting noisy-so I stopped using it.  It is good for the bench and constant loads-but musical surges don't cut it anymore.

Again the best thing is not to try and bandaid the situation and use the correct gen and you don't have to worry.
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Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Jonathan Johnson

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Re: Generator and Amp protection?
« Reply #23 on: November 19, 2011, 03:46:22 pm »

GENERALLY SPEAKING, Watts are watts, makes NICE conversion tools.

Gensets are rated in volt-amps, not watts. Kilowatts are equal to kilovolt-amps ONLY for resistive loads; inductive loads can draw higher kVA than kW. The conversions for kW are what aren't so nice.

Still fairly simple, though-- multiply amps by volts and you get VA (A * V = VA). (A * V = W) only for resistive loads; for inductive loads, (A * V != W) due to power factor.

But you're safe to ignore all of that nitpicking and multiply the volts by the amps your devices draw to determine the kVA rating of the genset you need.
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Jeff Bankston

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Re: Generator and Amp protection?
« Reply #24 on: November 19, 2011, 04:11:39 pm »

Gensets are rated in volt-amps, not watts. Kilowatts are equal to kilovolt-amps ONLY for resistive loads; inductive loads can draw higher kVA than kW. The conversions for kW are what aren't so nice.

Still fairly simple, though-- multiply amps by volts and you get VA (A * V = VA). (A * V = W) only for resistive loads; for inductive loads, (A * V != W) due to power factor.

But you're safe to ignore all of that nitpicking and multiply the volts by the amps your devices draw to determine the kVA rating of the genset you need.
+1 watch the terminolgy. the gens we rented were rated in KW. step down transformers like 480 to 120/208 are rated in KVA. my amps have both watt and amp draw on the back for the AC power. circut breakers and panels are rated in amps. it can get confusing. Home Depot sells a neat little pocket book called "UGLYS" with good electrical info and formulas in it. another thing you need to take in account is voltage drop if your running long power cords. VD is calculated by the length of wire run-gauge of wire-voltage-# of phases-amp draw. the uglys book has those formulas in it. 
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Ivan Beaver

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Re: Generator and Amp protection?
« Reply #25 on: November 19, 2011, 04:20:08 pm »

Gensets are rated in volt-amps, not watts. Kilowatts are equal to kilovolt-amps ONLY for resistive loads; inductive loads can draw higher kVA than kW. The conversions for kW are what aren't so nice.

Still fairly simple, though-- multiply amps by volts and you get VA (A * V = VA). (A * V = W) only for resistive loads; for inductive loads, (A * V != W) due to power factor.

But you're safe to ignore all of that nitpicking and multiply the volts by the amps your devices draw to determine the kVA rating of the genset you need.
ANd then rent the next size up-just for overhead.  It is nice not to be running at max and you never know what else may need to be plugged into it-non audio or lighting related but still part of the event.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Robert Weston

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Re: Generator and Amp protection?
« Reply #26 on: November 19, 2011, 06:22:33 pm »

you are right, fuel makes no difference, quality of gen does.

Correct - my original comment referenced a higher reliability (and much, much quieter operation) with diesel generators rather than gas.
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g'bye, Dick Rees

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Re: Generator and Amp protection?
« Reply #27 on: November 19, 2011, 08:15:52 pm »

Correct - my original comment referenced a higher reliability (and much, much quieter operation) with diesel generators rather than gas.

My Honda gasoline generators run as quiet or quieter than any of the diesel gen sets I've had to use, with the possible exception of a brand new Onan unit I once encountered.  Of course, they are smaller units, but size was not mentioned.  Only gas vs diesel.  As to reliability, I think that is a quality of construction and design issue unlinked to fuel type.

Both types require proper maintenance and I would agree that a diesel engine will have a longer useful life than a comparable gasoline engine.  But I cannot agree that gasoline generators are louder and less reliable.  There are other factors that come into play well before that.

It's just too much of a "blanket indictment" to hold up........
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Todd Rasmussen

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Re: Generator and Amp protection?
« Reply #28 on: November 21, 2011, 09:02:49 am »

most cheep gens use an inverter like you buy for your car or truck to convert 12vdc to 120vac. this is awful power and not suitable for anything more then a light, microwave, or bullitproof milwaukee power tool.

I can't speak to the type of inverter used in most inverter gensets, but not all 12V inverters produce awful power. I have a 1kW Samlex pure sine wave inverter mounted in my work truck for some instrumentation stuff I use. The power is quite likely cleaner than what comes from the grid. Granted this is not power enough for a big show, but I have run some smaller audio gear from it and it worked perfectly.
« Last Edit: November 21, 2011, 09:05:17 am by Todd Rasmussen »
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