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Noisy power from typical backup generators
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richard.cs:

--- Quote from: james_s on February 25, 2021, 08:52:47 am ---I don't have any 240V loads on the portion of my panel that is on the transfer breaker and neither does he but it wouldn't cause any problems, they'd just get 0V just as you'd expect. ... I fail to see how it is dangerous to feed both legs of the panel from the same wire. There's a physical interlock on the breakers so the generator breaker cannot be turned on while the utility main is on, and the bridge is in the socket on the end of the cord that goes from the generator to the house.

--- End quote ---
I don't see the issue here either, the jumper is on the interlocked side so you never get the situation of the grid seeing a line-line short. 240V loads getting 0V isn't dangerous, so what's not to like?*

<UK>*Well, apart from the use of 120 V and the whole split phase system itself.  ;D </UK>
james_s:

--- Quote from: Renate on February 25, 2021, 12:00:20 pm ---Ah, camping, back to nature, peace and quiet.
For some Americans that apparently has no appeal.
No, this photo is not from a rock concert only a little camping site.

--- End quote ---

There are different kinds of camping. I don't typically take a generator along but it can be handy to have for longer trips at campgrounds that lack amenities, especially if there's a trailer that has an air conditioner or even just a couple of fans and you're in a hot place in the summer, those turn into an oven during the day and it's handy to be able to charge up batteries or run various devices. I wouldn't bring it for a weekend of tent camping in the woods, some people are a bit ridiculous about such things but thankfully most of those sort of campgrounds don't allow generators.
Johnny B Good:

--- Quote from: EmptyHead on February 25, 2021, 06:34:18 am ---
--- Quote --- Incidentally, I did toy around with the idea of installing an electric start circuit to drive the PM alternator as a BLDC starter. I even got so far as to invest 16 quid in a 60v rated 300W electric scooter BLDC control unit with both Hall effect sensor and sensorless control options. I could get it to spin at about 480rpm using a 48v battery pack but only by removing the spark plug. Even blocking the spark plug hole with my finger whilst it was running was sufficient to stall it, proving that sensorless operation wasn't up to the task of handling such erratic mechanical loading.
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I have a Honda EU2200i that I want to electric start so the lady can easily start with push of a button. Using the PM alternator as the starter motor is of particular interest. Any pointers you can share on this?
I would be interested in using a 12VDC lawn mower battery or Dewalt 20V max 9AH battery or Dewalt 60V 3AH battery(20v max 9ah)

First time post for me.

--- End quote ---

 One of my reasons for investigating the possible use of the alternator as a BLDC starter motor was because the inverter module just happened to completely block easy access to the hex nut that typically retains the flywheel and cooling fan onto the end of the crankshaft, preventing the use of the classic "cordless drill with hex socket and extension" starter trick.

 Believe me, If it had been possible to use the cordless drill trick, my electric starter project would have been nothing more than an interesting "Thought Experiment. I'm nothing if not pragmatic about seeking an improvement over that accursed pull start with a recoiling rope bodge that some dope back in the last century thought would be good enough for small outboard motors and which, sadly for us all, was adopted as "An Excellent (dirt cheap to implement)" starter method on almost every small ICE powered gadget from chain saws to weed whackers and moderately sized gensets. The electric (cordless) drill trick would have served me just fine, thank you very much!

 If you're lucky with that EU2200i in being able to access the crankshaft nut by drilling a strategically placed hole in the case by which to insert a suitable hex socket on an extension adaptor, that might be all that's needed to take the strain out of starting on the pull cord by your good lady. Mind you, there's some small skill required to disengaging the "starter" in a timely fashion and the direction of rotation as seen from that end of the crankshaft should ideally be clockwise to minimise the risk of accidentally undoing the fan/flywheel retaining nut (although I think I may overstating the risk - best ask others experienced in the black art of electric drill starting for their considered opinion on this).

 Inverter gensets designed for 120vac output generate only half the voltage used by UK and EU "230" volt inverter gensets making such modification a little easier to implement. This gives you more voltage margin when adapting a cheap 20 dollar 300W rated electric scooter BLDC controller module designed for battery pack voltages only as high as 60v since you only need to power it from a 24 to 30 volt starter "battery voltage".

 The time you have in which to isolate the module between first power stroke and the revs accelerating to a dangerous voltage output speed is much greater since not only is the slope of this voltage increase gentler, you also have a larger difference between the 24/30 volt and the engine speed point at which the 'back EMF' becomes too high for the module's output transistors to handle without damage.

 It just might be possible to replace the existing output transistors (usually power FETs in these modules) with higher voltage rated devices (600v in my case or 300v with a 120vac output inverter genset) to proof it against the normal alternator output voltage without the complication of an add on relay isolating circuit. However, this does depend on how the High Side drive voltage circuitry is implemented so making a cheap commodity 60v rated BLDC controller HT proof will likely be a little more complicated than merely swapping out the half dozen 80v rated power FETs for 300 or 600 volt rated ones.

 For a given 1KW rating, one would expect the stator windings resistance of a 240v inverter generator to be four times greater than that of its 120v counterpart. When I was testing this out some 18 months or so back, ISTR stator resistance values of 7 or 8 ohms with an unloaded (spark plug removed) current draw from my 48v battery pack of just under half an amp at 480rpm.

 I calculated a starting from standstill current draw of 4 amps peak and a half unloaded (cranking) speed to demand a little over two amps. In the case of a 120v 1KW inverter genset, you can expect at least a doubling of these amperage figures using a 24 battery and likely another 50% more for a 2KW rated genset.

 I did check out drive modules designed for VFD use with 600v rated output devices but it wasn't certain whether they could still function reliably (or at all) off a 48v supply (they'd normally be powered from rectified and smoothed mains voltage, 350vdc from 240vac or 170vdc from 120vac supplies) so I didn't pursue this avenue of research any further since these drive modules weren't cheap.

 Anyway, that's the stage I reached before I lost interest over 18 months ago. As I said previously, I might take another look at cracking the sensored commutation problem come the warmer summertime weather conditions. I had hoped initially that my electric start upgrade could avoid any mechanical modifications to the engine/generator assembly itself but it looks like I'm going to have to at least remove the fan cowling to access the flywheel to test the viability of using hall effect sensors to detect flux leakage from the embedded magnets which is more of a strip down than I've so far attempted.

 Since I'll need to strip the outer covers off anyway before I can look to getting access to the flywheel, I'll take another look at the possibility of shifting the inverter module to allow cordless drill access to the crankshaft flywheel/fan retaining nut. I may have given up too easily the first time round on this approach to the problem of starting it electrically. It's been over 18 months since I last saw the internal arrangement - perhaps with enough determination, I might find a way to relocate the inverter module to allow the use of a cordless drill for starting it up. Sometimes the simplest solutions turn out to be the most optimal in the end. ::) :popcorn:

John
IDEngineer:
That's a lot of work to avoid pulling on a rope. Not that I don't appreciate a good DIY project.

Might be simpler to start it with a shot of compressed air.

There's also a starting system, by Honda(!) I believe, in which you precharge a spring with multiple gentle pulls on the rope. Then a button uses the spring to aggressively dump the energy into the crankshaft for starting. Essentially mechanical leverage with a delay, via energy storage, in the middle.

As for decoupling your starter system once the engine starts and spins up, that's exactly what a Bendix system on a starter does. Those usually extend and retract to engage a gear on the edge of the flywheel, but seems like you could install a coupling on the end of that same shaft to first engage the crankshaft to start the engine, and then retract once the engine overrevs the Bendix mechanism. In other words, install them in line and engage axially instead of radially.

Just some random thoughts, worth exactly what you paid for them! {grin}
james_s:
Well the EU2000i definitely uses a 3 phase permanent magnet alternator so it shouldn't be too hard to spin it with a BLDC controller. You don't need anywhere near the power level it is designed to generate in order to turn over the engine for starting so you might get away with a considerably lower voltage. Normally I think electric start is a pointless gimmick that adds considerable cost, bulk and weight and I actually quite like the elegant simplicity of a recoil starter, no battery to haul around or keep charged, no separate starting accessory to keep track of, just pull the self contained cord and it starts. In the case of a generator that already has most of the hardware present it makes a lot more sense though, just add a battery and a few extra parts and firmware on the inverter board. Hybrid cars have been using combined alternator/BLDC starter units for years.
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