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[g'bye, Dick Rees]

Everyone knows I don't allow personal attacks on this forum, so maybe he was just having a bad day. However, this is something that could get really dangerous in a hurry if not done correctly, so you're in the right place to ask these questions. Think of it as your parents yelling at you to get off of the train tracks...

Mike Sokol (moderator)

I look at it like this:

If you're going to put your personal pride ahead of public safety, you've no business messing with power or anything with liability issues in the first place.  I'm not here to sweet talk anyone into rationality.  I just speak to the issue regardless of whether it hurts someones feelings or not.

Safety first.

[frank kayser]

I look at it like this:

If you're going to put your personal pride ahead of public safety, you've no business messing with power or anything with liability issues in the first place.  I'm not here to sweet talk anyone into rationality.  I just speak to the issue regardless of whether it hurts someones feelings or not.

Safety first.

Sage advice.  No artificial sweeteners.
Wrong place for rubber-stamps on your ideas.


Welders make fine construction generators. Saws. Drills. Battery chargers.
Construction generators seldom have the voltage and frequency regulation one would want for electronic equipment.
Most (all?) construction generators produce less than the ideal waveform for clean power.
Will it work?  Most likely.
Ideal? Far from it.
Will your equipment be damaged?  There's a better chance of loss with this type of genny than the above mentioned Honda 7000is.
Is it safe?  I'm not qualified to answer that.  Without a G-N bond, I believe a GFCI will offer no protection.  (someone correct me if I have this wrong!!!)
It's not a setup I'd choose to use.
I come from a Quality Control background.  One recurring theme is that there is never enough time/money to do it right, but money and time are always found to do it over.  That is, if you have the chance.  Safety does not always allow a "do over".


FWIW
frank

[Tim McCulloch]

I look at it like this:

If you're going to put your personal pride ahead of public safety, you've no business messing with power or anything with liability issues in the first place.  I'm not here to sweet talk anyone into rationality.  I just speak to the issue regardless of whether it hurts someones feelings or not.

Safety first.

The stern talk from Uncle Dick is appropriate.

[g'bye, Dick Rees]

The Genny will be a Lincoln electric commercial grade welder/generator. I believe it's around 10kw-12kw. Plenty for this event. It seems to put out pretty stable power. From what I found it is not ground to neutral bonded.

Here's my red flag.  This citation is so casual and uninformative as to raise questions about attention to detail.  As a "bonus", we get a gross assumption..."it seems to"...

But it IS  good to know that there is no N/G bonding...which would lead me to dismiss it as a power source right away.

Jason is doing the right thing coming here to check things out and I give credit where it is due.  I certainly would not want him to get discouraged and NOT ask any questions.  But as I said, I call 'em like I see 'em and if the truth hurts, so be it.

I started working construction as a teenager back in 1960 and am quite familiar with welding rigs.  They are NOT to be used for non-construction purposes.  Even then, they can be mis-used fatally.  This I have seen first hand...

[Frank Koenig]

(big iron gear is probably ok, but I'd worry about SMPS gear, it may not like the voltage steps.)

I've heard this suggestion before but I don't understand the physics behind it. Switch mode power supplies generally have a line-voltage rectifier and capacitor-input filter as their first stage. It seems to me that this topology would be relatively insensitive to input voltage waveform. I'd be more concerned about the inverter's ability to supply the high peak current at the top of the voltage waveform that results from the use of a capacitor-input filter. The inverter might die, not the SMPS.

Big iron, which I take to mean line-frequency transformers as the first stage, might actually be more sensitive to the input waveform. Someone more familiar with power transformer design might comment on the effect of harmonics on core losses and subsequent heating.

I'm not in the welder/generator (as opposed to a welding generator) debate. I'd look at the specs and design of the generator and make a decision. I recall that Miller has some pretty deluxe Diesel powered welder/generators which would not surprise me if they made fine, frequency and voltage regulated sine waves.

After thought: Dunno about SMPSs with power factor correction circuitry. They might not like a crummy waveform, but, on the other hand, they're only found in high end gear that tends to be pretty robust.

--Frank

[g'bye, Dick Rees]

Frank...

Nothing lets the magic smoke out of sound gear faster than welding/construction generators.

Nothing has been quite so amusing as watching DJ's attempt to run on these rigs, happily creating their "thump-thump" for an hour or so before the sound goes away and a cloud of black smoke rolls out of their amp rack.

[jasonfinnigan]

When I said it seems to be stable power I mean I check the voltage output It was well within the normal +/-10% from 120 volt (granted no load was on it.) but I'd be more worried about the wave not being @ 60hz than voltage. It'll blow up the power supplies in no time with the harmonics overheating them.

Is anyone familiar with the Ingersoll Rand G20? We can get one of those easily. This is why I wish they just did the stuff on the festival grounds (we have about 3 of them here) rather than the mall. They all have great 3 phase power with Cam lock hookups and Single phase hookups as well.

[Jonathan Johnson]

Pay attention to the other guys discussing the power quality issues with the generators. They know of what they speak.

As for grounding, it sounds like you've got a difficult situation. An alternative to driving a ground rod in the island is to dig a trench and bury it horizontally. Normally this should be at least 2 feet deep, but if it's an irrigated planter where the soil is kept reasonably moist, you could probably get away with 1 foot deep.

I say "probably" because I am not an electrical engineer, licensed electrician, or inspector, and nothing I say should be construed as advice from any of those disciplines. I'm just tossing out ideas; verify with a trusted source first.

If driving or burying a ground rod or bonding to some other grounded structure such as a light pole or fire hydrant simply isn't possible, I can think of two other (horribly expensive) workarounds:

1. Insulate every electrical device from the ground using rubber mats. The rubber mat must extend far enough so someone can't touch the device and the ground at the same time.

2. Cover the entire area with steel plates and "ground" to that (think "deck of an aircraft carrier"). Of course, all of the steel plates must be electrically bonded.

[g'bye, Dick Rees]

When I said it seems to be stable power I mean I check the voltage output It was well within the normal +/-10% from 120 volt (granted no load was on it.) but I'd be more worried about the wave not being @ 60hz than voltage. It'll blow up the power supplies in no time with the harmonics overheating them.

Is anyone familiar with the Ingersoll Rand G20? We can get one of those easily. This is why I wish they just did the stuff on the festival grounds (we have about 3 of them here) rather than the mall. They all have great 3 phase power with Cam lock hookups and Single phase hookups as well.

The IR G20's seem to be very popular for back-up power for municipalities and on paper would seem to be MUCH more preferable for your use.  It should be acceptable.

As to the "cleanliness" of the welding generator, you'd have to 'scope it thoroughly.  +/- 10% is not stable in my book.  I'd much rather see +/-2%.  And you really need to look at the THD to get any idea of suitability, not just the gross specs of voltage and frequency.

[Frank DeWitt]

2. Cover the entire area with steel plates and "ground" to that (think "deck of an aircraft carrier"). Of course, all of the steel plates must be electrically bonded.

Almost unrelated but AC power distribution on US navy ships are ungrounded.

320-1.2.1.1 System Grounding. All ac distribution systems on U.S. Navy ships are ungrounded. However, cer-
tain avionics shops, aircraft servicing systems, and landing craft air cushion (LCAC) servicing outlets are sup-
plied from three-phase, four-wire systems that are supplied by transformers with a grounded, wye-connected sec-
ondary and single-phase, three wire grounded outlets with two pole ground fault current interruption (GFCI)
protection are provided where required by the user equipment (see paragraph 320-1.2.1.3).

Only one ground con-
nection point is allowed for each grounded power system. Ungrounded electrical systems have no intentional
connections between the electrical conductors and the ground (ship’s hull). These systems were chosen for their
higher reliability because grounding of a single conductor will not typically produce enough fault current to
interrupt power. Grounds must be removed as soon as possible to maintain this advantage, however, because a
second ground on another phase will cause a power loss and could endanger personnel.

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