| Electronics > Projects, Designs, and Technical Stuff |
| Petrol Generator Mod - Inverter AC Output |
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| WanaGo:
--- Quote from: schmitt trigger on January 28, 2019, 04:40:17 pm --- 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. --- End quote --- Yep lesson learned about the angle grinder, it was a poor choice, but I would have come to this position at some point, so better at the very start than when I actually needed to power something. Thanks for the reply. I need to do some more reading on the subject. |
| WanaGo:
--- Quote from: Johnny B Good 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. --- End quote --- That's unfortunate. However, that said, my time is free to me and this was a learning exercise more than anything. The inverter itself was not expensive, and the company that sold it to me actually offered it for free if I could make a video on the project after I have it working, but I don't think that's going to happen given the results so far. --- Quote from: Johnny B Good on January 28, 2019, 05:22:52 pm --- 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). --- End quote --- That makes sense, damn. I guess this 2 pole generator was never going to cut it. I was naively hoping that rectifying it to DC would remove a number of issues with the limited poles, and then inverting the DC back to AC would then just work. But obviously I have a lot to learn. Which I guess what the whole purpose of this. --- Quote from: Johnny B Good on January 28, 2019, 05:22:52 pm --- 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). --- End quote --- Yep but again that's not the purpose of this at all. I didn't just want to buy something. This isn't something I need to use, it was more of a learning project for me. Buying something teaches me nothing. I was trying to learn from this, and if failing is the way to do that then I guess I am succeeding. It would be nice though to get this working, but from what I am reading I may never get there. I guess I need to do more research on the subject and find out exactly what is going on. As mentioned, I would have assumed that rectifying to DC and then inverting the DC back to AC would have solved limitations with the old generator. Maybe the DC doesnt have enough 'storage' to cope with surge, but maybe the inverter is just too simple to handle surge anyway. Maybe some power resistors would help limit surge current, but is that a good idea? I dont know. This isn't something I want to keep throwing money at, and to date hasn't cost me very much at all, but if there is something more I can do to at least get something out of it, I can convert the generator back to how it was pretty easily, and have the traditional AC output for most things, and have a more limited inverted output for smaller more sensitive loads, then I guess that could be a comprimise. I don't know what the best solution is. I just want to try and understand why this failed more than anything. If its rated to 2000W then in what situation would that actually be viable? A slowly ramping load, rather than anything with surge above this limit? If anyone has any more ideas on what I could try, then I would love to hear. This FPC stuff I really have no idea about, what it is, where it typically is in a system etc or what it does. Thanks All |
| Circlotron:
Somewhat off topic, but it would be cool if someone made a portable inverter generator with 3-phase VVVF output that you could use to drive a 3-phase induction motor. |
| WanaGo:
Just been googling and came across this youtube video, and just wanted to pick brains on the concept conveyed. So this guy seems to improve PF by using a Run Capacitor on the AC output of the Inverter he has. It seems the Run Cap would change depending on the equipment being run, but I am curious if this concept could be put into practice as a general output capacitor of the inverter to help deliver surge currents to protect the FET's, along with maybe large current limiting power resistors. So off the top of my head, he used something like a 20uF cap for his Freezer, and something like a 90uF cap for his drill press, and it improved the PF considerably. If I was to say put a 25uF run capacitor (which I happen to have one sitting here) on the output of the inverter, would that in theory help deliver current for surge startup on some devices, and help limit the surge loading on the FET's? Obviously it's not perfect as different devices will demand different caps, based on what he showed in the video, but could it help protect the inverter FET's? As what suggested above, power resistors might also help... If I was then to also put say a 5ohm power resistor of suitable sizing on the output of the inverter, before the capacitor (this is likely totally wrong math but say 220V / 40A = 5.5ohm), that might help limit the maximum current pulled out, right? Is this thinking totally wrong, and all I end up making is a basic filter which does nothing useful and I will still blow FET's ? Be nice :) Thanks |
| WanaGo:
More googling https://www.ametherm.com/inrush-current/inverter-inrush-current-protection |
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