Author Topic: Petrol Generator Mod - Inverter AC Output  (Read 10651 times)

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Offline WanaGoTopic starter

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Petrol Generator Mod - Inverter AC Output
« on: January 08, 2019, 03:38:17 am »
Hello,

I am after some assistance in a project I am working on.

I got an older 'Silent' Petrol generator, which has a Honda GX120 engine in it, and a 1400W Alternator of sorts, which is 2 pole, and has 220VAC 50Hz and 12VDC 8A outputs.
Looking at the outputs on a scope, they are not very pretty at all. The DC doesn't at all look like DC, but when put on a large cap it smooths out nicely.
The AC is, well, just yuck. I guess this is just how generators of this era were before the inverter ones came on the market.
It works fine when you connect a Drill or Light etc, but I don't suspect it would be very good for more sensitive equipment.

The generator does not 'talk' to the motor, its all governer based, and the motor purely runs at a set 'ish' RPM, and the 3000RPM basically translates into 50Hz based on 2 pole - I believe.

So what I am planning to do is bypass the current AC outputs, rectify the winding phases directly into DC, and then invert the high voltage DC into a more pure sine wave AC. I guess this is just typical stuff really.

The problem I have is most Inverters in the lower price bracket are designed for 12VDC or 24VDC to 220VAC, and not so much for 300+VDC input.

I have been scouring Aliexpress and I found these:

https://www.aliexpress.com/item/Aiyima-2000W-Modified-Sine-Wave-to-Pure-Sine-Wave-Inveter-Board-Driver-EGS002-AC16VDC380V-to-AC220V/32845887806.html

https://www.aliexpress.com/item/2000W-Pure-Sine-Wave-Inverter-Power-Board-Post-Sine-Wave-Amplifier-Board-DIY-kit/32334756548.html

https://www.aliexpress.com/store/product/Aiyima-2000W-Modified-Sine-Wave-to-Pure-Sine-Wave-Inverter-Inverter-Finished-Board-with-Heat-Sinks/1756394_32847801786.html

There are a few others too.
These take a 380VDC intput, along with a low voltage AC (which looks to be rectified and regulated into DC) to power the electronics on the board, which I think are 5VDC based, and you get a Modified or Pure Sine Wave AC output.

I am basically after some input as to what people think. Do these boards look OK? The descriptions are not the best, but you can kind of get a feel that they are using the same sort of Driver boards on them, but the base boards vary a little.

There was also this one, which uses the same Driver board again, but it has some images of them hooking it up in a test situation and a scope:

https://www.aliexpress.com/item/2000W-Pure-Sine-Wave-Inverter-Power-Board-Post-Sine-Wave-Amplifier-Board-DIY-kit/32728282834.html

Am I going about this the right way or is there an easier path?

For the 12VDC output of the generator, I plan on just passing this through a switching regulator, to get a stable 13.8V or so out, to charge batteries etc. I might even make the adjustment more accessible so I can turn the output voltage as required for what I end up powering.

So the main bit I am stuck on is the AC side and how to clean it up, and if this rectified into DC and inverted with something like the above boards, is the way to go.

Any suggestions welcome.

Thanks
 

Offline james_s

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #1 on: January 08, 2019, 05:37:02 pm »
If you just want to have a big complicated DIY project to show off your abilities then it could be interesting to try, otherwise you will spend far more effort than it is worth and end up with something that likely doesn't work as well as the cheapest Chinese inverter generators on the market. Those older style generators work fine when noise isn't a problem, the output looks a bit ugly on a scope but I have used one before to power lights, refrigerator, tv, computers, etc without issues. They are still popular unfortunately, on the rare occasions when the power goes out here there are at least a dozen of them roaring away within 20 minutes of the outage. The incessant din is unbearable, I can't hear myself think. This is probably worse here in 60Hz land where conventional generators scream at 3600 RPM.
 

Offline ConKbot

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #2 on: January 08, 2019, 06:44:02 pm »
What do you want to run that's a "sensitive" load?  Most computers, and switching power supplies are just going to rectify it to a 340ish volt rail internally, so the benefit of another rectify/invert stage for general use seems dubious.

If you must, though, get a 2kw inverter of whatever price point you prefer and get to hacking. I've done a overhaul on a broken 3kw square wave one i picked up for cheap, it's was just a 2 channel push-pull converter to get the +/- DCV rails, and an IGBT H-bridge for the output. If you could externally supply the DC rails and maybe bypass some undervoltage detection circuits if needed, you could probably trick one into working with either external HVDC or 12/24V in.

Id suggest not going for an absolute cheapest unit, as I worked on a 2kw unit also, that its MSRP was much cheaper than the 3kw one and it was a ratsnest of wires and PCBs and quite miserable to even disassemble. Vs a single PCB and a couple wires to connectors on the 3KW unit.
 

Offline DrDeke

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #3 on: January 08, 2019, 09:57:47 pm »
If you're open to a different approach, it might be cheaper (and easier) to buy an old double-conversion UPS and connect it between your existing generator and the load.

Here in the US, an old 2 kW double-conversion UPS like a Liebert UPStation GXT or GXT2 can be had for about $100 on eBay. They tolerate being powered from my extremely cheap petrol generator and run on inverter full time to provide a nice output. These particular models don't even seem to need a battery installed to perform this function (although they would obviously lose power immediately in that condition if your generator stops).

These exact models won't work for you, they only work on 100-120 V input (unless you get a 10 kW+ unit, which sounds like overkill in your situation), but perhaps you could find something similar that is designed to work with 220 V.
 

Offline DrDeke

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #4 on: January 08, 2019, 11:39:40 pm »
These take a 380VDC intput, along with a low voltage AC (which looks to be rectified and regulated into DC) to power the electronics on the board, which I think are 5VDC based, and you get a Modified or Pure Sine Wave AC output.

For what it's worth, I think the output of a "modified sine wave" inverter will probably be worse for your loads than the original output of the generator would be. (That is, to the extent they would have a problem with the generator's output in the first place.)
 

Offline james_s

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #5 on: January 09, 2019, 02:27:58 am »
These take a 380VDC intput, along with a low voltage AC (which looks to be rectified and regulated into DC) to power the electronics on the board, which I think are 5VDC based, and you get a Modified or Pure Sine Wave AC output.

For what it's worth, I think the output of a "modified sine wave" inverter will probably be worse for your loads than the original output of the generator would be. (That is, to the extent they would have a problem with the generator's output in the first place.)


It definitely will. I have a modified sine wave inverter and it makes transformers buzz badly, and years ago I blew up a cordless drill charger plugging it into one of those. The output of a cheap generator doesn't look very good but it's not as bad as it looks.
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #6 on: January 09, 2019, 12:35:09 pm »
Thanks for the replies everyone.

So this unit I have is not a Chinese knockoff, its an Italian made machine (better/worse haha I dont know), it has a genuine Honda GX120 engine in it, and I cant find any branding on the generator alternator side of things.
Its quiet, you can have a conversation while standing next to it. I have not yet found a date of manufacture yet, and the Italian company who seems to make it 'Airmax Generator Division, Italy' does not seem to feature on Google, or has closed down. There is a name plate on the side, which is 9402 which could indicate 1994 or 2002 potentially.

Under the cover of the alternator it has an 8uF Run Cap for the field I guess, but nothing else on the output stage. The DC side has a single phase bridge rectifier, but no capacitor on its output, so that is nasty looking on the scope too. I guess that is designed to be plugged in to a battery to charge it, or into a device which has decent input filtering. When you put a cap on it unloaded, it stabilises to a more DC looking signal, but does vary somewhat when the RPM deviates a little on the engine. Its actually around 24VDC when unloaded with a cap on it, but comes down with load, much like a transformer I guess. I regulated it down to 13.8V and the output is nice and stable, just when I was testing things.

So going back to the AC side, yeah its not very nice, and I can appreciate what has been said. They are what they are, and they do power things I know. I am not wanting to upgrade for any particular reason than to have a project and improve what I have. Yes buying new will get me better I know, but thats not what this is about.
I have powered a fan, a drill, some lights etc, and no issues from what I can tell. The output on the scope however is really not great. Here is a bit of a pic of it, in differential mode with math CH1-CH2. I only have 1x/10x probes, so excuse the poor shot.



Here is one of the DC, unloaded, without cap.



The thing I don't like is the varying frequency. As load comes on and off, the motor RPM changes, and then it reacts and it goes fairly stable again. There is no comms on this unit, no feedback between the generator side and the engine, its just a governer. If you get a bit of crap in the fuel, or it starts running out of fuel or something, the revs change, and the motor might conk out if the fuel runs dry etc, but during that period the frequency is all over the place. My fear is what might happen to 'something' connected to it which is more sensitive.

I don't have a particular load in mind, its just something I wanted to bring up and see what people think.

When I got the generator the engine had bad blow-by, the carb was totally gummed up, it was leaking oil, and a few other typical maintenances related issues. The insulation under the covers powdered when you touched it. So I honed the cylinder, got a new piston and rings and gasket set, ultrasonic cleaned the carb and rebuilt that, and now it runs brilliantly. Replaced the insulation, and basically gave it a total work over, it was good fun. So I did that last week, and while I had it out I thought I would attempt to get the output to be 'better', and that's when I stumbled on those links from Aliexpress.

What I can't make out from the Aliexpress stuff is if they are Modified Sine Wave output, or Pure Sine Wave Output, and if you need any other 'bits' other than the board itself. The links suggest both modified and pure, and then some have some instructions on some sort of modification, but I cant follow what its talking about. There are some cheaper ones, and some more expensive ones. I have just found another one which seems another step up but I have not figured out what the actual difference is yet.

https://www.aliexpress.com/item/High-Quality-3000W-Pure-Sine-Wave-Inverter-Power-Board-Post-Sine-Wave-Amplifier-Board-Assembled/32888215704.html

Would love to know thoughts.

Given the generator is 1400W, I imagine if I rectified to DC and inverted back to AC again I am going to lose some capacity. I guess I could have a switch to change between raw output or inverted output, depending what I power off it.

This is just a bit of fun and to learn something new, I have never done anything like this and I know little about inverters.

Here is a bit of a video of it running just after I put it back together a few days ago. https://streamable.com/t77d3

Thanks
« Last Edit: January 09, 2019, 12:42:14 pm by WanaGo »
 

Online Zero999

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #7 on: January 09, 2019, 01:18:24 pm »
I can't see of any easy way of doing this. It's going to be a quite complex project.

An inverter will boost 12V or whatever to 340VDC, before converting it to 230VAC. It should be possible to modify an inverter to take 340VDC and convert it to 230VAC by bypassing the internal DC:DC converter and using a switched mode power supply to power the 12VDC control board. The 230VAC from the generator could then be rectified and used to power the inverter. The problem is the output from the generator isn't regulated and there'll be lots of ripple, so you'd need a switched mode power supply, rather than a simple rectifier.
 

Offline soldar

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #8 on: January 09, 2019, 03:45:28 pm »
The model is Still 2000

Honda made the motor

Airmax made the generator and controls.



You could probably fit huge low pass filters on the outputs.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Offline james_s

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #9 on: January 09, 2019, 06:28:30 pm »
Don't obsess over the small details, just use it, it appears to be working more or less as designed. The varying frequency won't bother anything unless you power electric clocks for extended periods. Did you check the waveform while powering a resistive load?
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #10 on: January 09, 2019, 09:03:12 pm »
I can't see of any easy way of doing this. It's going to be a quite complex project.

An inverter will boost 12V or whatever to 340VDC, before converting it to 230VAC. It should be possible to modify an inverter to take 340VDC and convert it to 230VAC by bypassing the internal DC:DC converter and using a switched mode power supply to power the 12VDC control board. The 230VAC from the generator could then be rectified and used to power the inverter. The problem is the output from the generator isn't regulated and there'll be lots of ripple, so you'd need a switched mode power supply, rather than a simple rectifier.

Thanks - but did you see the links I posted? These already seem to take the HV DC input, so its just a case of rectifying it, which I already have a 150A 1500V rectifier. The board takes a 15VAC input to power the control board, which is rectifies to DC (you can input 12VDC on many of them too). My thoughts were to rectify the AC from the generator into DC, add some capacitance to smooth it out, and feed it into the inverter board (one of which I linked), and take the 12VDC output of the generator and regulate that and power the inverter controller with that. To me it seems straight forward, but I just have no idea if the boards on Aliexpress do what I think they do.
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #11 on: January 09, 2019, 09:05:12 pm »
The model is Still 2000

Honda made the motor

Airmax made the generator and controls.



You could probably fit huge low pass filters on the outputs.

Thats correct, its the STILL2000. This was the only video I could find on the internet of the unit before I brought it.
I put a little video of mine running on Streamable, https://streamable.com/t77d3
It has a badge on the bottom of the frame too for an Auckland company, who I assume imported and distributed them at some point.
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #12 on: January 09, 2019, 09:12:41 pm »
Don't obsess over the small details, just use it, it appears to be working more or less as designed. The varying frequency won't bother anything unless you power electric clocks for extended periods. Did you check the waveform while powering a resistive load?

Not sure 'obsess' is what I am doing here. Yes, I could just use it as is, but that's not the purpose of the post.

I have only run motors (fans and drills) and lights on it so far, I haven't extended to much else yet. I haven't wanted to put anything I am willing to destroy on it yet. When I did the tests a few days ago, it was after I had read some stories about blowing gear up due to the poor waveforms, so I haven't yet ventured out to powering much more yet. Later today I will try a few other load types and look at the waveform as I do so. The ultimate aim is to be able to run a stick welder or MIG on low settings, on it. The Stick welder I have is a small DC inverter unit, so if that can run directly then that would be great, just not sure if it has the grunt to power it. Will find out soon I guess.

The power almost never goes out here, so its purpose in life is not so much for backup power in blackouts, is for using gear away from a power source.
 

Offline DrDeke

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #13 on: January 10, 2019, 02:38:27 am »
It seems to me like part of your implied question is as follows: "Is it bad/harmful for my appliances to run them on (non-inverter) generator power?"

My power does go out somewhat frequently, which has led me to have this same question. I have not been able to find much in the way of good information about this. (I have a very inexpensive non-inverter generator which, at least in some circumstances, does not provide a very clean AC waveform.)

I see disclaimers from generator manufacturers, saying that "sensitive equipment" may not be suitable for use with their inexpensive generators, but it's hard to know how much stock to put in that.

I see a lot of posts [note: not on eevblog; I mean on other Internet fora] from people who sound relatively uninformed, claiming that cheap-generator power is very bad for all kinds of equipment. Then I read many of those same people claim that a cheap standby or line-interactive UPS will "clean up" such power and make it "safe" for equipment. As far as I can tell this is clearly not the case, which makes me question the claim that cheap-generator power is "bad" for equipment in the first place.

I also see a lot of posts from people saying something along the lines of "I have a cheap generator and I always unplug my computers when I have to run it, but I run everything else on it and have never had a problem." This seems encouraging. Even if the generator power damaged one of my computers, the damage would almost certainly be confined to the power supply, and those are easy/cheap enough to replace, so...

I have been running almost all of my electrical equipment off the cheap generator when need be, and all I can say is, none of it has broken yet. I don't think my generator is powerful enough to run my central air conditioner but, since those are rather expensive, that is probably the only piece of equipment I wouldn't risk with what I've seen so far.

From reading the replies so far to your thread, it seems like people here are somewhat skeptical that the power from your generator is likely to harm your appliances. I would certainly be interested in hearing any additional input people have on this topic; maybe that input would be useful to you, as well.
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #14 on: January 10, 2019, 04:51:19 am »
Spot on, thank you.
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #15 on: January 10, 2019, 05:01:26 am »
The other side of the question is about these Inverters I linked.

I got a reply from one of the sellers, who explained they are designed to convert Modified Sine Wave AC into Pure Sine Wave AC.
But they appear to do so by rectifying the Modified Sine Wave back into DC again to start with.
So this is where my logic of, if they are just inputting essentially HV DC and creating a Pure Sine Wave output, then I could do the same from my generator, rather than doing what its designed for and coming from some sort of Modified Sine Wave device.
They then talk about getting 16VAC by wrapping a few turns around the transformer (I assume which is in the first stage in the Modified Sine Wave device) to get this out, then the 16VAC is fed into the board, rectified and filtered into DC and regulated down to 5VDC for the driver board to run off. You can see this on some of the photos, and one of the boards even mark where the DC input can go instead of feeding in 16VAC. So I could feed in DC from the 12V supply of the generator for this.

There are a lot of smart people on here, so I was hoping that someone could have a peek and see if they think that logic sounds reasonable from what is shown on the links.

Thanks
 

Offline james_s

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #16 on: January 10, 2019, 06:01:39 am »
I have a similar Chinese pure sine inverter board that I use to get 240V 50Hz power over here in 60Hz land. It works ok, however I had to make some modifications to get it to perform adequately, the mosfets and the output filter inductor it came with were crap. It also needs a reasonably well regulated DC voltage input in order to get the correct voltage output.

Computers are not particularly sensitive, the modern switchmode power supplies are very robust and they run just fine off cheap generators. The noise and fuel efficiency is crap but I've never had any problems at all running any sort of equipment off old style generators. If I was on a tight budget and wanted an inverter generator and didn't mind using questionable Chinese parts, I'd just buy a Chinese inverter generator, apparently the ones Harbor Freight sells are decent, certainly it's gonna be better than something you could build yourself. Trying to convert a standard generator you wouldn't get the greatly reduced noise and fuel consumption which is the whole reason inverter generators are so much nicer.
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #17 on: January 28, 2019, 07:30:30 am »
Hi James_S,

With your inverter, what specifically did you have to change on yours?
Was it FET/Transistor related, or something else?

To All,

I ended up getting an inverter and had it running on the bench, and all looked great really, output was really good etc. I initially tested it at 12V, then 30V then upped it to 200V and then powered it off my generator after rectifying the AC. I put on a small 40W load, everything still good. Then I put on an 850W load from a power tool, and it died. Spun for a moment, then all just went silent. The Generator started kicking like it was under incredible load. The Inverter is rated to 2000W, but I wonder if the surge current has killed a weak component. It was an angle grinder, so I can imagine the inrush is pretty high, but I wouldnt have thought it would have done what it did. The symptoms would suggest one of the transistors has died, to me at least.

The inverter has Infineon 47N60C3 transistors, 650V 47A 0.07ohm RDSon (https://www.infineon.com/dgdl/Infineon-SPW47N60C3-DS-v02_06-en.pdf?fileId=db3a304412b407950112b42dff93492f) on it, the large TO 247 package. However I brought the inverter as a kit, so built it myself. Immediate alarm bells when I saw the transistors, as the legs were cut and they had solder on the legs. Looks like its a classic case of recycled materials. Anyway, had no choice so just assembled it anyway and hoped for the best.
Wonder if one of those transistors has failed ON and is now basically a dead short and not letting the thing pulse away like it should.

The DC input takes 380VDC sort of region and has 2 electrolytic caps on the input. Normally they hold their charge for hours and hours, I tested it the other day about 4 hours later, and the input was still over 250VDC. I will be mounting a 1Mohm resistor across it as a slow drain I think. Anyway, after it stopped working, the input is 0V, so there would seem to be a short circuit. I'll investigate more soon.

For another project I had some of these, and still have 3 in my box of parts, same TO 247 package. https://www.infineon.com/dgdl/Infineon-IPW60R041C6-DS-v02_01-en.pdf?fileId=db3a304327b897500127f24dd83c3c09 . These ones dont look recycled, but did not come in tubes either. Legs are full length and no solder on the legs.
Curious if these would be an appropriate replacement part to use for the dead one, and if I should try swapping one out with one of these. Just not sure if its wise to mix or not. Assuming one is dead of course.

I also have 4 of these IGBT's from another project, but unsure if these are any better for this application. https://www.infineon.com/dgdl/irgp4063dpbf.pdf?fileId=5546d462533600a401535655ee0c2450, same TO 247 package again. These sort of look recycled too, tinned legs but they are full length.

Never really played with this kind of HV stuff and learning as I go. So please bear with me.

Thanks
 

Online Zero999

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #18 on: January 28, 2019, 12:53:05 pm »
Yes, it was probably the surge which killed it.

Why use it on an angle grinder anyway? No doubt it has a universal motor which will be happy with the crappy distorted sine wave from the generator.

If you powered the inverter from a rectifier and smoothing capacitor, then the power factor would be poor, which would explain why the generator struggled. Have you checked that it wasn't the rectifier which died?

Ideally you need an inverter with a 230VAC input and 230VAC output, with power factor correction.
 

Offline james_s

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #19 on: January 28, 2019, 04:39:27 pm »
My inverter came with counterfeit mosfets of unknown specs which I replaced before building it. Then I found that the output inductor was undersized and would saturate well below the rated load. It was overall not a very good design.
 

Offline schmitt trigger

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #20 on: January 28, 2019, 04:40:17 pm »
As British mountaineer George Mallory's famous quote: "Because it's there", I think I can understand the reasons why some individuals pursue certain goals which appear to be preposterous at first glance.

It will be a difficult journey, but if you succeed, you will:
  • Learned many things, both practical and theoretical, that otherwise you would not have learned.
  • Feel really proud of your accomplishments. Also, and this is quite important, your children and grandchildren will also do

Now, my two yen on this subject.
Power tools most likely utilize series-wound universal motors. They generate very significant amounts of noise, due to the brushes. Additionally and this is most important, they draw very large surge currents.

I would advise that you go to E-bay and purchase a bank of power resistors, such that you can do all sorts of troubleshooting without worrying -at first- about your load. Later, you can add in parallel some motor-run capacitors, to simulate a lagging power factor.
 

Offline james_s

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #21 on: January 28, 2019, 04:48:10 pm »
What you really need for any sort of workable solution is very fast current limiting that will both limit the instantaneous current and trip completely if the average current exceeds a safe value for the mosfets.
 

Offline Johnny B Good

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #22 on: January 28, 2019, 05:22:52 pm »
 Take it from one who knows from bitter experience, you're wasting both time and good money.

 It looks like your generator is an AVRless, self excitation type which probably gives it some  immunity to the capacitive loading effect from the PFC and emi filtering used in modern smpsu powered IT kit which sends the more sophisticated AVR type of genset into gross overvolting.

 For instance, the 8.4μF's worth of capacitive loading on the 230v input of my APC SmartUPS2000 would cause my 230v 2.8KVA genset to generate in excess of 270v which the UPS rejected, removing the capacitance when it switched to the battery, followed by the voltage going back to 230v and the UPS switching back to the generator to start the next yo-yo cycle.

 A simple self excited (by that 8μF capacitor?) generator is already making use of that overvolting phenomena which should minimise the effect of such capacitive loads that make the more expensive AVRd gensets "unsuitable for use with IT kit" (it's not noisy or badly distorted waveforms or even bad frequency stability that the UPS makers use as an excuse for the problems they cause with such 'cheap gensets' - 30 to 120KVA gensets can't be classed as 'cheap'! - it's this overvolting response to leading current (capacitive) loadings present in most IT kit's PSUs and in the larger amounts to be found  in the older line interactive UPSes such as that vintage pure sine wave output (purer than the mains supply!) APC SmartUPS2000 of mine.

 With regard to your proposed conversion to inverter power, I'm afraid you're not going to see any benefit since what makes the inverter type genset more efficient and noticably quieter on no or quarter/half loadings is the use of a multi-pole (typically 6 or 7 pole pairs on the runner with 18 or 21 pole piece windings on the stator) three phase permanent magnet generator head feeding a full wave 6 diode three phase rectifier to generate the required low ripple 200 or 400 vdc used by the 60 or 50 Hz inverter (basically a pair of back to back high voltage class D amps in H bridge output configuration, driven from the required 50 or 60 Hz reference sine wave generator).

 Furthermore, a lot of weight and space savings made in these designs is realised from the use of an out runner bolted directly onto the engine shaft to act as a flywheel very much like the arrangement used by the old Seagull outboard motors with magnets embedded into the flywheel as part of the magneto ignition used to spark the two stroke engine. The little 1KW/1.2KW rated Parkside unit mentioned below only weighs a mere 13KG (dry - a full 4.5 litre tank of unleaded adds just under 4Kg to the all up weight).

 The 18 or 21 pole stator is bolted straight onto the engine casing end to feed the high voltage three phase full wave rectifier integrated into the inverter module which is more than just an inverter, including as it does, a microprocessor to monitor oil level and control the stepper motor driven butterfly throttle on the carburettor to control engine speed to match the electrical demand placed on the PM alternator by the inverter's response to the electric loads plugged into its outlet(s).

 Basically, I'm advising you to invest your money in an off the shelf inverter genset rather than wasting it on your folly of a project which can only succeed as an educational exercise in "Learning from your mistakes". There are surprisingly cheap inverter gensets available these days (long gone is that accursed Honda monopoly in such kit) but you still need to be wary of the Workzone shite (to name but one).

 I eventually solved my problem with the original  4 or 5  year old  "Backup to my UPS based backup project by purchasing a 1KW continuous / 1.2KW (30 seconds peak) rated Parkside inverter genset (the 2nd generation PGI1200-B2 model) from my local Lidl store for just £99.90 in May last year. This little beauty, as I knew it would, didn't suffer the temperamental voltage effect of the earlier conventional 2.8KVA unit I'd had such a terrible experience of those 4 or 5 years back.

 I'd have preferred a higher rated inverter genset but these were typically 3 to 5 times the price of the little PGI1200-B2 for just twice, at best, the continuous power output rating. I'd spent the just less than 100 quid basically just to prove that an inverter type genset was THE solution to my problem (I knew the inverter wasn't going to respond with an overvolting reaction to leading current loadings like my previous genset had - the rest, frequency stability and waveform distortion and even "noise" were never ever the issue with my UPS).

 A few months later, Aldi put their 2000W Workzone inverter gensets on sale at just under 3 times the price so I took a punt on one, discovering just what a pile of excrement these were after sampling three different ones. Believe me, those Workzone units were total rubbish making the Parkside unit a shining example of inverter genset perfection by comparison. Actually, in hindsight, the PGI1200-B2 is inverter genset perfection just on its own merits. The only downside compared to a Honda inverter genset being the 10dB or so higher noise levels but, at a 900 quid saving in purchasing cost, I can happily live with that trivial downside. :-)

HTH & HAND

Johnny B Good
« Last Edit: January 28, 2019, 05:30:41 pm by Johnny B Good »
John
 

Offline coppercone2

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #23 on: January 28, 2019, 06:00:22 pm »
Lol they make analog cctv malfunction pretty hard. Pc will be fine.
 

Offline WanaGoTopic starter

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Re: Petrol Generator Mod - Inverter AC Output
« Reply #24 on: January 28, 2019, 07:58:37 pm »
Yes, it was probably the surge which killed it.

Why use it on an angle grinder anyway? No doubt it has a universal motor which will be happy with the crappy distorted sine wave from the generator.

If you powered the inverter from a rectifier and smoothing capacitor, then the power factor would be poor, which would explain why the generator struggled. Have you checked that it wasn't the rectifier which died?

Ideally you need an inverter with a 230VAC input and 230VAC output, with power factor correction.

Thanks for your reply.

Angle grinder, as it was at arms length, rated to 850W, thought in my head that I can run up to 2000W and didnt give it much more thought than that.

Rectifier didnt die, still OK. I did think that too, but checked it out and all is OK. Its rated to 50A and something like 400A surge.
http://www.eicsemi.com/datasheet/KBPC5000_10.pdf the KBPC5010 version.

Disconnect the DC incommer to the inverter, and its still making over 300VDC out of the Rectifier. Connect the inverter again and we have problems.

I have no clue what Power Factor really is or PFC, so I need to do some googling. Thanks for your reply.
« Last Edit: January 28, 2019, 10:18:54 pm by WanaGo »
 


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