Electronics > Projects, Designs, and Technical Stuff
Petrol Generator Mod - Inverter AC Output
schmitt trigger:
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.
james_s:
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.
Johnny B Good:
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
coppercone2:
Lol they make analog cctv malfunction pretty hard. Pc will be fine.
WanaGo:
--- Quote from: Zero999 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.
--- End quote ---
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.
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