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Author Topic: Portable generator operating in the rain.....  (Read 6282 times)

Tim McCulloch

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Re: Portable generator operating in the rain.....
« Reply #10 on: June 25, 2019, 08:25:24 pm »

I think the key thing here is how much headroom you have with the generator (and sound system).
If you are too close to the limit you are going to get excessive voltage swings.
It may be that you can load an inverter unit more than a similar rated conventional unit without undo issues.

When the inverter is out of current, it's out.  What the control circuit does determines how graceful the recovery.  Long term, if the batteries can't be charged faster than the current is drawn, it's over even if you can keep the inverter circuit from failing.

Abrupt and significant changes in loading a diesel powered spinner has both voltage and line frequency impact.  The inertia in a big rotating mass helps, but this is why load banks accompany some types of generator usage.  Kind of analogous to "phantom loading" for resistance plate dimmers back in a previous century...

We spec a minimum generator of 20kW MQ for most events without PoCo service. 
« Last Edit: June 25, 2019, 08:31:03 pm by Tim McCulloch »
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Jonathan Johnson

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Re: Portable generator operating in the rain.....
« Reply #11 on: June 26, 2019, 04:08:56 pm »

In another generator thread recently the same question was raised and it seems the opinion of the electrical experts was that any decent quality generator would be good and that mirrors my experience...

The problem with small non-inverter generators (maybe <7.5kVA?) is that they don't handle sudden load changes well due to their relatively small rotating mass. If the load change is great enough (as might happen with a large bass thump), the frequency and voltage could be driven outside of the operational limits of the connected equipment. Nobody cares if a skilsaw takes a little longer to get up to speed because the generator slowed down, but it can cause electronics to reboot.

The larger generators have greater mass (and engine torque) which helps them to regulate frequency and voltage, so “inverter” technology isn't as necessary.

If you can minimize the load changes, a small standard genny might work OK.

There could be issues with floating neutral (not bonded to ground) or interconnects with separately-powered devices, but there ways of dealing with that.
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Rob Spence

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Re: Portable generator operating in the rain.....
« Reply #12 on: June 26, 2019, 05:12:51 pm »

The problem with small non-inverter generators (maybe <7.5kVA?) is that they don't handle sudden load changes well due to their relatively small rotating mass. If the load change is great enough (as might happen with a large bass thump), the frequency and voltage could be driven outside of the operational limits of the connected equipment. Nobody cares if a skilsaw takes a little longer to get up to speed because the generator slowed down, but it can cause electronics to reboot.

The larger generators have greater mass (and engine torque) which helps them to regulate frequency and voltage, so “inverter” technology isn't as necessary.

If you can minimize the load changes, a small standard genny might work OK.

There could be issues with floating neutral (not bonded to ground) or interconnects with separately-powered devices, but there ways of dealing with that.

I am curious... where does the inverter generator get the instant energy for a bass drum hit? It has a rather smaller rotating mass.
I agree it will maintain frequency.
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Marc Sibilia

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Re: Portable generator operating in the rain.....
« Reply #13 on: June 26, 2019, 06:12:21 pm »

I am curious... where does the inverter generator get the instant energy for a bass drum hit? It has a rather smaller rotating mass.
I agree it will maintain frequency.
It can use the energy stored in the capacitor bank between the generator and the inverter.  It can also pull more current from its generator windings and slow down even more than a syncronous generator, using the rotational kinetic energy without varying the output frequency.
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Mike Sokol

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Re: Portable generator operating in the rain.....
« Reply #14 on: July 13, 2019, 06:52:40 pm »

I am curious... where does the inverter generator get the instant energy for a bass drum hit? It has a rather smaller rotating mass.
I agree it will maintain frequency.

Inverter generators are actually DC generators that make about 12 volts DC (IIRC). So yes, there's a capacitor to take the current hit. Some of the Yamaha's actually had a small 12-volt battery in the circuit to act as a "super capacitor" of sorts. This also allows them to idle back with reduced loads. Then all the capacitor/battery needs to do is supply enough extra current for a few seconds, which allows the gasoline engine to come up to full RPM, and make full current.
« Last Edit: July 14, 2019, 08:06:09 am by Mike Sokol »
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Brian Hancock

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Re: Portable generator operating in the rain.....
« Reply #15 on: August 30, 2019, 08:40:41 pm »

Using generators in the rain is perfectly fine provided safe cabling practices and elevation from standing water you will see movie sets, commercial shoots, large scale concerts etc etc etc all on generators... the real issue here is appropriately oversizing your generator for the purpose and draw it's being used for ... most generators large dino squishers are 80% power factor corrected meaning you dont get 100% of the x number of listed kw this is typically in a constant draw situation not a fluctuating load ... and some things are more forgiving... par cans dont care ... power amps yes in many situations do.

You can just scale this appropriately so if you have a 1800w powered speaker you probably shouldn't use a 2000w generator but if you have 3 575 pars probably be ok 
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Jerome Malsack

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Re: Portable generator operating in the rain.....
« Reply #16 on: September 05, 2019, 01:17:50 pm »

unless I have missed it,  Most outlets feeding to outside house or basement are on GFI.   So should the Generator have the same GFI protection especially in the rain ?  And most of the cables are basic edison without  RV or moister protection. 
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Stephen Swaffer

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Re: Portable generator operating in the rain.....
« Reply #17 on: September 06, 2019, 12:51:23 pm »

GFCI protection outdoors and around water is always a good idea.  A lot of guys (and gals) -myself included-are reluctant to use GFCI on mission critical circuits.  I am more willing to do it these days-maybe because GFCI reliability has improved-and maybe because age has caused me to value safety over lack of embarrassment. (could be that I've crashed enough on my own that something I can genuinely blame on something else is a relief too)!
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Craig Hauber

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Re: Portable generator operating in the rain.....
« Reply #18 on: September 25, 2019, 01:49:17 pm »

dino squishers

Is this an autocorrect from "dynamo" or something?
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Tim McCulloch

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Re: Portable generator operating in the rain.....
« Reply #19 on: September 25, 2019, 03:11:36 pm »

Is this an autocorrect from "dynamo" or something?

Dinosaur, as in liquid hydrocarbon pumped from the swamps of history.  I presume the "squish" refers to diesel ignition.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

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Re: Portable generator operating in the rain.....
« Reply #19 on: September 25, 2019, 03:11:36 pm »


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