120V/240V AC Output Quality Of Welders

Has anyone hooked up an oscilloscope to the AC outlets of an engine driven welder? How clean is the output? Could you run a computer,
radio, television, or laser printer off it?
__________________ Note: To reply, replace the word 'spam' embedded in return address with 'mail'. N38.6 W121.4
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'mail'.
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Barry:
I have been researching the same thing for almost a year and all the info I can find says the quality just isn't there to run sensitive equipment. From everthing I have read if you need clean power to run the more sensitive newer appliance/computers etc. you need a good quality inverter style generator. I'm sure there are some good quality very expensive construction grade engine driven welders out there that would do the job nicely but they are out of my price range.
I have an old Miller Big 20 engine welder with a single outlet and a Coleman 5000 watt generator and I was looking to replace them with one single unit but look s like it's not that easy if clean power is required.
Jimbo

'mail'.
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<to the thread>
That's why I have * 2 * UPSes. <G>
Actually I have my answering machine on one of them.
I don't know what you're doin' but that oughta solve the problem.

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This may be astupid question but what's a UPS
Jimbo

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Jimbo wrote:

Uninteruptable Power Supply. Battery backup for a computer system in case of power failure.
Cheers Trevor Jones
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Jimbo wrote: 1. Never a stupid question. It is smart to ask!
A UPS is "Un-interrupted Power Supply" - e.g. battery backup wall plug. The battery drives an inverter that then drives the load that is plugged in. It also has a high level of line interference and line hit protection.
I have two in this room that I sit in now. Two computers and two printers and two monitors.
The one on this system has 37 minutes it can handle the load and keep up. That also means that I have xx minutes or more to fire up a shaver, a radio whatever I want when the power is out. Mountain house so it happens here.
I have my TV, DVD, Tape deck, DVDBurner, PDA all plugged into a protected socket(s) - not battery backed up ones. They protect from voltage spiking that occurs on the power line almost every day - everywhere!
Martin

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Obviously something worth looking in to.
Thanks
Jimbo

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Jimbo wrote:

Here is a link to a former employer you can learn more than you ever wanted to know about UPSs off their site.
http://www.powerware.com/USA/default.asp
Be warned there are a number of different designs for UPSs and most will not function from a DC output generator check with the manufacturer. Most will not function properly with a laser printer attached, the in rush is too high from the laser printer. UPSs are allot like welders there is a big difference between consumer and industrial products and you do get what you pay for.
Doug Hamilton
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snipped-for-privacy@shaw.ca wrote:

Or go to www.apc.com
Martin
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These FAQ's are pretty good too. http://www.powersentry.com/faq2.html http://www.tripplite.com/support/faq/tech_surge.cfm One thing I learned that left me feeling frustrated is that the protecting varistors wear out and most devices will provide no protection when they are gone so you never know if the one you have is doing any good or not.
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These FAQs address my comments about getting what you pay for. Better products have built in diagnostics and alarms to warn you when components fail. The most important feature if you have concerns about power quality from your generator is to get an on-line or double conversion UPS. These units convert all incoming AC into DC then convert it back from DC to AC so you have complete isolation from the input to the output. Machines that are sold as "Off-line", "Stand-by" should be avoided unless cost is the most important factor, the protection is not much better than a surge suppresser power bar with the bonus of battery back up. "Line-interactive" machines are the middle ground providing a little more protection by basically conditioning the line power by suppressing the surges and boosting the sags and with varying degrees of filtering depending the quality of the machine for other line garbage. Line-interactive machines tend to get over worked when connected to a noisy generator or a generator that the frequency or voltage wanders allot, depending on the machine it may shut down, fail, or go to bypass none of these condition is desirable.
Doug Hamilton
Zorro wrote:

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Earlier this winter we had a huge storm in the Seattle metropolitan area which knocked out power in many places. My son had a major school paper due the next morning, and it (about 40 pages) only resided on the hard drive of my PC. Our first step in coping with the impending disaster which would have ensued had he failed to turn in his paper on time was to unplug my PC and drive it to a job site where we used the power of a generator/welder unit on the back of a truck to bring up my PC and copy the paper to a floppy. The generator, which brand I don't recall but it was a lot like a Miller Legend, powered my computer perfectly. Don't forget, your computer doesn't actually *use* AC, everything is transformed and rectified to +/-12VDC and 5VDC.
(He took the floppy to the city library where we did the final edits and printed the paper out. Feeling tremendous, he took it to school the next day only to find that the teacher had granted extra days due to the storm and he just couldn't face working on it any more. He ended up barely passing, which is much more a reflection on his school than his paper - I know, I read it very carefully indeed.)
I suspect a printer would work fine. Anything with an AC supply in it like a radio or TV I would wonder about.
Grant Erwin Kirkland, Washington
Barry S. wrote:

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One could put a protection UPS unit between generator and a computer. Most are small and would be good to protect from spikes or surges.
I have a 1KW one under my desk now - shares were my feet would kick around. :-)
Martin
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We have a house and shop full of stuff that runs off two different types of inverters and occasionally from two different generators, one of which is an 8kW Hobart welder/generator. Very few problems. X10 (sensitive) is only happy with the best inverter output, but OK on both of our generators. Some clocks might not be happy if your generator isn't well governed, especially if the load fluctuates. No problem with computers, they're quite happy to run off even cheapy square-wave inverters by most reports. You might search the archives of alt.energy.homepower, lots of discussion of the topic.
List of our loads etc. at http://www.citlink.net/~wmbjk/07solar_power.htm
Wayne
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I have a Miller Bobcat. The scope says the output is as pure a sinewave as I see from the utility company. That's to be expected since it is an alternator, what else could it be? The frequency varies around a bit (function of engine RPM), but only things like electric clocks and old phonograph turntables care much about the frequency being precisely 60 Hz. Voltage regulation is pretty decent at light to moderate loads, about +/- 5%. With a heavy switched load, I've seen voltage momentarily drop as much as 15%. All of that is acceptable, and comparable to what you'd get from the utility with a slightly undersized service drop.
Computers all use switching power supplies, so they don't much care if the power is clean, exactly on frequency, or well regulated (within reason). They convert the AC directly to DC, chop it at a high frequency, step it down, and rectify and regulate it again at the 5 and 12 volts the computer's electronics actually need. Sinewave, square wave, or even DC is acceptable as input power as long as the voltage is relatively close to nominal (+/- 20% or so).
CRT monitors can be a different story. Some aren't regulated very well, so line voltage variations can cause the picture to expand or collapse, or go out of convergence. You may also get traveling hum bars if the frequency is off. The amount of regulation they have isn't always a function of price either. I've seen some expensive monitors show these problems, and some cheap ones which didn't. It is just a matter of how the designer of the particular model felt about good power supply design. In general, LCD monitors don't suffer these problems, and are much less power hogs too.
Laser printers generally use switching power supplies, so the comments above about computers apply to them too. They do require a lot of power compared to a computer or monitor, so there could be problems with a marginal generator.
Ink jet printers usually use a wall wart power supply, which while it is a switcher too, is generally not a very classy switcher, and may not produce good results if the frequency or voltage is too far off nominal (I haven't had any problems with my Canon and HP ink jets running on the Bobcat, though).
The same sorts of comments apply to radios and TVs too. Tape players may wow a bit with changes in line frequency. CD players generally don't care.
I use my Bobcat as backup power for the house. It runs all my computers, TVs, TiVos, satellite receivers, ham radio gear, etc, as well as some lights, refrigerator, freezer, furnace blower, and central air conditioning. The voltage dips a little when one of the bigger loads switches on, but not enough to cause any problems.
If several of the bigger loads switched on at once there might be a problem, but that hasn't happened to my knowledge while I've been running on the generator. For sure none of the computers has ever rebooted, nor has one of the TiVos lost a program it was recording, while I was running on the generator. I do try to practice power management, and don't try to run everything at the same time.
I was a little concerned that the central air might be asking too much from the generator since its starting surge is right at the full rated output of the generator, but it has handled it without complaint. I suspect Miller's ratings are a bit on the conservative side. It sure is nice to be able to sit in air conditioned comfort watching TV while all the neighbors swelter in the dark.
Gary
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wrote:

<snip>
Nice post Gary.
Thanks.
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After reading Gary's post I'm beginning to think this clean power thing isn't as critical as I have been led to believe.
Jimbo
wrote:

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Jimbo wrote:

I think so too. Many of the ATX power supplies available today will run on 90 to 240 volts with no adjustment.

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wrote:

How loud is the Bobcat? Too loud to sleep at night with it on?
__________________ Note: To reply, replace the word 'spam' embedded in return address with 'mail'. N38.6 W121.4
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