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How can I clean some dirty AC from my generator?


bobleny
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I'm not sure if this is the right forum to put this in, I'm not even sure if this is the right site to post this in, but I have a diesel generator that produces 120V AC via a badly regulated alternator. It was actually causing our ACP UPS's to go nuts and click on and off repeatedly. I finally got the chance to hook it up to an oscilloscope and found out why. It looks kind of like a really bad stepped sine wave.
Here is a really bad illustration of what it kind of sort of almost looks like:
generatoro.png

Unfortunately, I didn't have the foresight to take a picture of it. It has the basic shape of a sine wave and the peaks are at about 175V, but all along the line it had several voltage drops similar to the ones illustrated above. I just showed the worst ones, very little of it, if any, is smooth Like I would expect.

So, I need to find some way of fixing the power. I would like something that I plug in line between the generator and the switch panel.

I did find a power conditioner by APC but I don't think this would do what I would like it do, defiantly not on the scale I would like it to work.
http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=h15&tab=features

I've read several posts in various forums on this subject and they all seem to say the same thing, you shouldn't have bought such a piece of crap. I was hoping you guys, who seem to be very knowledgeable would be able to provide a better insight.

Any ideas?
Why is it so are to make dirty AC pretty?

Thanks!

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That's not too bad, it appeard to be EMI, possibly generated by the ignition system, rather than distortion which would change the overall shape of the waveform.

A capacitor probably wouldn't do much because the imedance of the generator to high frequencies wouldn't be enough. An inductor in series and capacitor in parallel will be much better.

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Sorry for the delay, I'm still trying to get a hold of the manufacture of my generator to see what they can do, if anything...


That's not too bad, it appeard to be EMI, possibly generated by the ignition system


Well, the graph I made only shows the worst couple of spots. There are spikes and dips along the entire have form. I was just really lazy in drawing the graph. On the good side though, it is very constant. It was almost like looking at a picture on the screen.

I don't know what you mean by ignition system. I know I didn't specify before, because I wasn't sure what the output rating is, but it is a 6kW pull start generator. As far as I know there is no ignition system. There is no battery and there are no glow plugs...


[...] An inductor in series and capacitor in parallel will be much better.


I'm not familiar with AC capacitors and I can only assume you need special inductors for AC as well.

I do remember building a DC power supply a while back in which I used a very specific formula, some capacitors, and some inductors to get my ripple to basically zero. Is there a different formula I need to follow with AC? I don't want to flat line my AC...

What kind of capacitors do I need? What kind of capacitance would I need?
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Sorry for the delay, I'm still trying to get a hold of the manufacture of my generator to see what they can do, if anything...



Well, the graph I made only shows the worst couple of spots. There are spikes and dips along the entire have form. I was just really lazy in drawing the graph. On the good side though, it is very constant. It was almost like looking at a picture on the screen.

Please post a photograph of the waveform.

I don't know what you mean by ignition system. I know I didn't specify before, because I wasn't sure what the output rating is, but it is a 6kW pull start generator. As far as I know there is no ignition system. There is no battery and there are no glow plugs...

Any petrol (gasoline) engine will have an ignition system, even if it has no battery. Diesel engines have glow plugs but no ignition system.




I'm not familiar with AC capacitors and I can only assume you need special inductors for AC as well.

An inductor is just a coil of wire, normally wound round an iron core to increase the inductance.

Non-polarised capacitors are required for AC.

I do remember building a DC power supply a while back in which I used a very specific formula, some capacitors, and some inductors to get my ripple to basically zero. Is there a different formula I need to follow with AC? I don't want to flat line my AC...

What kind of capacitors do I need? What kind of capacitance would I need?

The best solution is to just buiy a ready made mains RFI filter.
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Please post a photograph of the waveform.

I will do that the very next time I get my hands on an oscilloscope.


Any petrol (gasoline) engine will have an ignition system, even if it has no battery. Diesel engines have glow plugs but no ignition system.

Sure, but not all diesel engines have glow plugs. This one for example does not.


The best solution is to just buiy a ready made mains RFI filter.


I suppose without seeing an actually picture of the output, it is a little hard to tell exactly what kind of distortion it is producing, huh?

I did hook up a Islatrol active tracking filter which is a "high-frequency noise filter with transient protection for critical loads," but  it had no real effect.

I will work on getting a picture of the output and continue to hold, one hour at a time, as my call is very important...  ::)
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So it's a diesel generator, not gasoline.

From what I've read, only large diesel engines don't have glow plugs but it doen't matter either way as glowplugs are just heaters ant don't produce any electrical noise.

All gasoline engines have spark plugs which can cause electrical noise if not suppressed properly but as it's a diesel engine, it shouldn't be a problem. Unfortunately, I don't know where the noise is communing from.

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So it's a diesel generator, not gasoline.


I'm not sure if this is the right forum to put this in, I'm not even sure if this is the right site to post this in, but I have a diesel generator that produces 120V AC via a badly regulated alternator.



From what I've read, only large diesel engines don't have glow plugs but it doen't matter either way as glowplugs are just heaters ant don't produce any electrical noise.

That and glow plugs are only used to start the engine. Once the engine is running they turn off.


Unfortunately, I don't know where the noise is communing from.


Do all alternators produce the a nice sine wave?
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  • 2 weeks later...

Hi guys,


Here are a few tips from my experience:

1- Try to get a generator that includes a 25' extension cord that is specially made for a generator. That is a big plus!
2- Some generators are somewhat weather-resistant with items like rubber flaps to cover the sockets. I think that is a good feature.
3- My generator started easily on the first pull every time. It may not be worth paying extra for "electric start".
4- Start the generator with nothing plugged in, then start appliances one at a time, starting with the largest load. (Or whatever the directions say)
5- Gas may be hard to find after a hurricane. Five gallon cans could last 2

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  • 1 month later...

What is the relationship between the voltage waveform presented and the load conditions?

Actually generators that produce quite a bad sine wave can easily be found. Especially this concerns those cheap two stroke gasoline models made in China(improper rotor's material, poor isolation of windings etc.)
All AC generators normally have some built-in voltage regulation system using their alternator's drive winding. This system may somehow conflict with UPS under certain load conditions.

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