Cleaning AC Power produced by cheap generator

I have a Coleman Powermate 5500W Generator. These are notorious for producing dirty power. I didn't know this until after I bought it and burned
out some electronic equipment when I attached it to the generator. I have now installed an MOV surge suppressor, but I had an idea that I wanted to run past all of you.
I know I can go out and buy a power conditioner, but how creative is that? I want to work with what I already have. So my question is this: I have a 1 HP, split phase, capacitor electric motor that I don't use for anything. If I attach the motor to the generator in parallel to my other loads, but on the line side of the surge suppressor (as opposed to all the other loads I'm attaching), will the constant, smooth-running back-emf produced by the electric motor give me cleaner power?
I know this isn't the most efficient way to do this, but would it work? I should note, there is no load device attached to the motor. Would adding a flywheel have any effect on the power cleanliness? I don't care that the motor wastes 4 amps just sitting there running with no load. I don't use the generator enough to make that a worthwhile consideration. My main concern is cleaning the power that my generator produces, without having to spend any more money on more equipment. Besides, we all like to tinker, right!?
I look forward to some good discussion on this. Also, other ideas using home-remedies for power cleaning are also welcome! Thanks!
-Peter P.
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Without first knowing why damage was created, then you cannot just wildly install protection. For example, was the damage created by too much phase difference between voltage and current? Or was it other harmonic problems? Was it due to too much energy in high frequency noise? Or was it due to excessive voltage for a long time? Voltage high enough and long enough to damage electronics but never high enough to be seen by the protector?
An MOV suppressor is designed for events that are quick and tend to occur more like once every eight years. A constant spike (say 60 times every minute) would degrade that protector before the week is out.
In short, no one can answer your question without first knowing what is considered electrically 'dirty'. If the generator is creating repetitive and destructive transients, then MOVs will not survive long enough to be a useful solution.
Furthermore, what electronics were damaged and where? Did these electronic devices even confrom to industry standards?
Peter wrote:

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These are all very good points. Unfortunately, I don't know the answer to most of these questions. But here is what happened last time:
I was running my generator near capacity for an extended period of time, backfeeding into my household. (Yes, I have a transfer switch and was isolated from the grid.) I had to leave to run an errand. When I returned, the generator had run out of gas (stupid me) and everything was without power. I noticed a funny smell in the house (you know, that wonderful burned circuit board smell) and looked to find the source. Grid power came back and I transferred back to utility power. It was then that I found the microwave, stove, and AC/furnace electronic controls all had the smoke let out of them. The total replacement cost was greater than the generator. I wonder, but don't know for sure, if this damage was caused during the generator's final moments of life before running completely out of gas. Conveniently, Coleman never made mention of this potential problem until I called them. Then they told me I should never backfeed into my house without using a power conditioner. Between the circuits I fried, the cost of the generator, and the cost of a 5500W power conditioner, I could have bought myself a top-of-the-line Honda generator and never given this issue second thought.
Lastly, the generator is not used regularly to power my house. The only times I need it is when winter storms take out our power lines up here in the mountains. This year it's happened 4 times, lasting from about 1 hour to 4 days. I used my AEMC harmonics meter to check for harmonic distortion and found it at less than 5%THD. RMS voltage is 125V. Frequency is between 60.5 and 61Hz. I haven't checked peak voltage , but I guess that might be another clue I should look into. Anyway, it was the Powermate tech support rep that said the generator power is "too dirty" to use directly in a household, but I don't know the details. Hope this sheds more light on the matter. Thanks a million!
-Peter P
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One possibility. Appliances must withstand 170 volts for 3 milliseconds without damage. So if the 120 volt generator were to suddenly output 180 volts for but a few seconds, then damage (and smoke) could result.
Not lets put the MOV protector on-line. But first read a number printed on the box. The let-through voltage is 330 volts. IOW the protector with a much higher threshold voltage ignores that destructive 180 volts. We have not solved the problem.
Another possibility - the 60 hertz power dropped to much lower (and potentially destructive) frequency. Maybe. But first we must identify what specific electrical components inside each appliance were damaged. Dead bodies are always best evidence. And still an MOV protector would have done nothing useful.
Solutions begin at the source - that generator. To solve that electrical failure, first learn why the generator may have (for example) created 180 volts for seconds. If you don't have the necessary equipment, technical support people, or knowledge, then you have no choice. Buy the superior Honda generator; your least expensive and most reasonable solution. It would be called, "Learning by example". Numbers (and your inability to get the necessary numbers) demonstrates one reason why the Honda is a more viable solution.
BTW your spec numbers say that generator is extremely 'clean' power. Computer grade UPSes output much 'dirtier' power when in battery backup mode.
Peter wrote:

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I agree with this statement up to a point. If the appliances were ON, under load during the low voltage low frequency event I can understand. Is your transfer switch 3 pole or 4 pole? Is the generator grounded? Is the generator ground common with the electrical service?
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How do you take your measurements? At idle, at full load, at half load? What you should to is start the generator, place about 50% load and then take your measurements. Set the voltage to ~125 v during this test. What the voltage is when it is idling is of no consequence.
I use to repair Coleman's as a factory authorized repair facility in the boonies of AZ. First NEVER run them for any length of time at more than 75-80% of load. Most rpm governed generator are not designed for long runs at "near full load". I used to go out to homes that had 5-10 kw units when they were shot. Similar to what you describe. Owners would come home start the generator, and start turning stuff on. Usually when the clothes washer went into spin cycle the Coleman's crapped out. Ever measure the starting current on a clothes washer when going into spin? We would repair them the first time under warranty. After that they paid for everything. Coleman's rules not the company I worked for. One maroon went out and bought 3- 7.5 kw peak power units and decided to parallel them. Oh what a mess that was.
Generator power "to dirty", bull shit. There are lots of places that use generators to power critical applications. Ever seen the backups at a hospital? We have 2 Caterpillar facilities here in Phoenix that are run completely by generators. Pretty good sales tool, hey come to my office and see how it is done.
If you really want power in the conditions you described. Start looking into diesels, and 1800 rpm motors, NOT the 3600 rpm lawn mower motors like the el cheapos.
Ok the last part of the statement was a little harsh. not much.
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I wonder if when his gen ran out of gas if choked for a bit...in other words started and stopped a few times under load instead of just cleanly stopping. This might cause a series of inductive surges.
I have run radio stations from small generators (not the transmitters of course) in emergency situations. No special surge suppression or filtering was used. the chief problems seem to involve computers and line frequency stability. Networked computers just don't seem to be happy unless they see good clean power. The UPS units i had also didnt like small gen power. They looked at the incomming power and decided to stay in battery mode until the batterys were exausted.
I'm in much better shape these days with a 15 kW continuous conversion UPS and a 100 kW Onan natural gas powered gen.
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Peter wrote:

Watching the generator output voltage on a scope under various load conditions would be worthwhile.
I have a Generac unit that has powered my house without a problem several times ... but your story makes me want to have a look at its output!
Roby
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| Watching the generator output voltage on a scope under various load | conditions would be worthwhile. | | I have a Generac unit that has powered my house without a problem several | times ... but your story makes me want to have a look at its output!
The larger generators typically do better in part because more goes into making them better quality, and part just because they are larger. I do recommend for whatever load you expect, your generator have double the capacity (triple if power single phase loads from a three phase generator wired in double-delta). If your home has 200 amp service (48 kW) you probably are NOT actually using all that. Find out what you do use and size for that. Then set the overcurrent protection on the generator at perhaps 75%. You don't plan to turn on every burner and the oven while the electric water heater is running with all the lights on during a utility outage, do you? OTOH, if you got a 100 kW generator, you could probably power a few other homes, too.
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<snip>

Many have discussed the quality of the power while the unit is running. But you didn't mention having any problems while running normally, only when the unit ran out of gas.
If I might suggest, when the unit is sucking air and the last dribbles of gas from the tank, it is probably running very erratically. A slug of air, the engine misses and slows, the governor goes wide open. Then another 'slurp' of gas and it fires a bit and over-revs. Add the frequency variations with the voltage regulator's swings trying to maintain voltage during all those rpm swings and *now* you have a mess.
If you want to experiment, put some large resistive load on it (one that won't be damaged by wide swings in volt/freq) and run the thing dry again. Monitor freq and volt as it starts to 'suck air'. I'll bet it goes all over the place for a several seconds before completely quiting.
Good luck daestrom
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I would agree with this. I once was trying to run the last few ounces of gas out of a small Coleman generator (2 or 2.5 kW) because I was going to store it for a while. I hooked up a 500 W halogen work light and fired up the generator. At first, it ran at a steady RPM and steady brightness. As it started to run out of fuel, the RPMs started running faster and slower at about 0.5-1 Hz, and the brightness varied considerably. It ran this way for at least a couple dozen seconds before dying completely. I didn't measure the output, though.
Matt Roberds
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daestrom wrote:

Now *that* makes sense!

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Hey everyone!
I just want to thank all of you for sharing your pieces of wisdom here. This discussion is great and I appreciate it. I'll continue to read and absorb all your advice as long as the threads keep going. Thanks a million!
-Peter P.
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I just have to say this:
Isn't Coleman a cooking and camping goods company ?
Seems they are living up to their code of cooking, only this time it was your fine electronics };-o
You should buy one of those " Wiremold Line Conditioners " ....... If it burns out quickly you can get a new one under warrantee ....
Other than that: The Coleman Company should offer a soution to this problem.
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