48VDC generator head
Comments
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Re: 48VDC generator head
Thanks Chris.ChrisOlson wrote: ».... and thermal and volumetric efficiency of the design.
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Chris
Combining all of the theoretical stuff like Otto versus Atkinson cycle and the practical stuff like fuel mixture, timing, breathing, etc.? An experimentally determined (dyno testing) or simulation-model-predicted map for a given engine based on whether you believe in models or not?
PS: Just because I know some buzzwords, don't assume that I know what I am talking about. I have a pretty good physical intuition and theoretical background, but little (no?) practical experience.SMA SB 3000, old BP panels. -
Re: 48VDC generator head
This thread (while waaaay above my head!) is why this forum is so great! Smart folks, engaging smart conversations about interesting stuff! Like I said before,, I learn something everyday!
Tony -
Re: 48VDC generator headCombining all of the theoretical stuff like Otto versus Atkinson cycle and the practical stuff like fuel mixture, timing, breathing, etc.? An experimentally determined (dyno testing) or simulation-model-predicted map for a given engine based on whether you believe in models or not?
Nope. The brake fuel map is actual measured on the dyno with a fuel flow meter. "Brake" means measured. Same as BHP (Brake Horse Power) vs a calculated value like SAE HP. One is measured, the other theoretical.
Interestingly, the "brake" part comes from the prony brake, invented by Gaspard de Prony to measure torque. I'm not sure exactly what year it was he invented it, but it remains the standard to this day and the calculations used for it are the same whether the dyno is wet brake, eddy current or hydraulic.
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Chris -
Re: 48VDC generator head
One thing I have decided about my DC generator project is that I am going to pick up a Honda GX200 for it. I left that Hatz diesel sitting outside so it got cold to see how hard it would start last night. It wouldn't start after sitting outside overnight without giving it a little wiff of propane out of my torch. I ran it and warmed it up for a bit, went in the shop - that thing is LOUD! I could hear in the shop plain as day and my shop is insulated really good.
It sounds like an old Briggs with a bad piston and about 1/4" of clearance on the big end of the rod.
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Chris -
Re: 48VDC generator headChrisOlson wrote: »The challenge is to simulate an off-grid cabin - we're going to charge a 232ah 24 volt battery bank (4 Trojan T105's) that starts out at 50% SOC, with a constant 1,000 watt load on the bank, to float, and see who can do it on the least amount of fuel.
We can do this right away - sort of. I'm waiting for my new batteries. It will be a 48VDC pack probably in the 400Ah territory. They're being donated in exchange for technical studies I'm performing. Therefore, the timing may be a few months away. I have an Alphagen DCX3000, which is based on the Honda GX engine. So when the batteries arrive, I can use the Alphagen straight away for the a direct-connect trial run. The Alphagen uses a PM alternator, so it's not nearly as optimal as our previously discussed configurations. But it will serve as a reasonable baseline.
I've never intended to use the Alphagen for absorption and float. That seemed like a waste to me. That's why I'd use an inverter generator hooked to the AUX inputs of the GS8048. It would serve as load support and topping off the batteries.
Here's another thought exercise: If I hang a Magnum MS4448PAE inverter on my Alphagen, it suddenly becomes an inverter generator? Great! So I have a combo 48VDC and 240VAC genset for about $3000! -
Re: 48VDC generator head
Well, I think what I'm going to use is a Wind Blew 520 instead of building a generator from scratch.
http://www.windbluepower.com/Permanent_Magnet_Alternator_Wind_Blue_High_Wind_p/dc-520.htm
Their output numbers are really suspect and you have to pay no attention to the man behind the curtain there, because he don't know what he's doing. But I know what these alternators are and they'll hit 150 open volts @ 3,600 rpm. They press the rotor apart and replace the slip rings and field coil with a neo ring mag, then press the claw pole rotor back together. The stator is a standard 24 volt GM stator wired wye and is .38 ohm. The stator is good for 44 amps and I only need 26.9 amps from it to build a 3.5 kW DC generator. The stator in this thing will dissipate 275 watts at 3.5 kW, which is hot, but it'll stand up.
I even get a "free" External Rectifier kit with it. ooooo....... I'm impressed. Might be able to use that for something but I need a better rectifier than that for this project. These guys that sell these things crack me up***. :roll:
I'll just put a LoveJoy on the shaft and direct drive it off the end of the crank.
**Features a 303 Stainless Steel Shaft for ultimate corrosion protection and increased power output.
Uhhhh........ Yeah........ Right......... I'd like an engineering analysis on how that SS shaft provides increased power output, please...........
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Chris -
Re: 48VDC generator head
Interesting discourse. Too bad I can't partake. I'm already sitting on a 24V 220Ah bank, and did initially start out with a GX200. But halfway through the build, I was teased with twice what I paid for the Honda, so I let it go. In the hunt for a suitable replacement, I happened across a neglected GX240. After some pencil pushin', decided it would be a much better choice anyway, considering the beefier internals of the GX240, and the charging parameters expected. This build is already making noise, but I haven't yet pulled any definitive numbers. Anyway, it'll be interesting to compare numbers when you guys reach the finish line. -
Re: 48VDC generator head
The 540 is what I use on my mini hydro. It's a great alternator for what it is, a reworked Delco automotive alternator. When I had it in wind service as it came on the infamous "Hornet', I kept it saturated with Rust Check, http://forums.redflagdeals.com/home-hardware-rust-check-spray-can-5-97-a-1025379/ by spraying inside and out once a year. As a result it stayed like new, while a neighbors corroded and aged badly in that same time.Rust Check has also kept my 10 year old battery terminals, connectors, nuts, bolts etc around the battery, like new for all these years. It was useless in wind service, other than looking real pretty against a clear blue sky, but has excelled with hydro.
Regarding the increased power output with the SS shaft, I have experience with that as well. The non SS shaft "shorts out" a good percentage of the magnetic field, resulting in less magnetic strength at the rotating poles. The SS shaft leaves the magnetic field intact, thus it's stronger at the rotating pole pieces. More power? That depends. For any given RPM, the unit with the SS shaft will produce more output, BUT! It's harder to turn than the non SS shafted unit, because of the stronger magnetic field. Because the SS unit is so much harder to turn, even under no load, even with adjusting speed ratios to suit the different units, the non SS shafted unit gives me a bit more power than the SS shaft ones. If you have lots of mechanical power to turn them, the difference means little, but when you've only got a little, the difference is definitely meaningful. I have 2 with SS shaft, and one non SS shaft. But it's the non-SS one I'm using because in my case, it produces more power. -
Re: 48VDC generator headwaynefromnscanada wrote: »The 540 is what I use on my mini hydro. It's a great alternator for what it is, a reworked Delco automotive alternator.
I could rework one here. But the donut mag is about $100 bucks. A new 24V GM stator is about $80 bucks. And I'd machine a shaft for it from 4130 CRM instead of stainless. And they put new claw poles in it and those are about $45 bucks each. I'm already to $270 bucks and I can just buy the thing for $299 and not have to mess with it.
Yeah, they're a perfectly fine unit for what they are. People try to use them for wind turbines, and that's pretty much a joke. But for hydro or gas generators they're great.
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Chris -
Re: 48VDC generator headwaynefromnscanada wrote: »Regarding the increased power output with the SS shaft, I have experience with that as well. The non SS shaft "shorts out" a good percentage of the magnetic field, resulting in less magnetic strength at the rotating poles. The SS shaft leaves the magnetic field intact, thus it's stronger at the rotating pole pieces.
I'd have to investigate, but I do find it doubtful. The ring mag used in the claw pole rotors is magnetized N-S on the ends or flat faces of the magnet. The shaft thru it is merely a core and the pole pieces direct the flux so none can "leak" past the pole piece unless it's saturated. The shaft itself cannot short flux in the air gap any more than these claws I put on my big ferrite magnet rotors, that hold the mags against centrifugal force, can:
Attachment not found.
I had a discussion with Hugh Piggot over this once and I proved with a gauss meter that these claws do not short flux in the air gap, or reduce it in the air gap in any way, shape or form. He was convinced that it "just can't be". But it is. The claws merely redirect flux from pole to pole on the same rotor that was leaking outside the perimeter of the rotor in the first place. In the case of a 17mm magnetic shaft it will just saturate - it is not a "black hole" that can soak up flux.
I'm not saying that your experience with them is impossible or anything - just that I'd have to see it with a gauss meter to visualize what happens. There's other reasons for an iron or steel laminated core generator to "turn hard" - one would be the use of a N38 vs a N40 or N42 disc mag in the rotor.
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Chris -
Re: 48VDC generator headChrisOlson wrote: »150 open volts @ 3,600 rpm
You gonna run that GX200 at 3,600RPM? According the the datasheet, the peak power is 5.5hp at 3,600RPM. So I guess you'll need to operate it WOT (Wide Open Throttle) to get full power 3.5kW on the output wires. The generator head is small. Sure you're not going to cook it? You are going to take a fuel efficiency hit by running on the power peak. Better to use a slightly larger engine (GX240) and operate off-peak at a lower RPM? But then you'll need to run more current through the head to compensate for low RPMs, which will cook it even more!
But that Blue sure is CHEAP! And so is the GX200. Now your Classic is the most expensive piece in the whole setup! -
Re: 48VDC generator headYou gonna run that GX200 at 3,600RPM? According the the datasheet, the peak power is 5.5hp at 3,600RPM. So I guess you'll need to operate it WOT (Wide Open Throttle) to get full power 3.5kW on the output wires.
The GX200 is a more fuel efficient engine - it's BSFC is .51 lb/hp.h compared to the GX240 at .70 lb/hp.h Trying to run an air cooled engine off it's peak will only result in more fuel burned/kWh produced. To get peak thermal efficiency the cylinder head temp has to get to 300-350 degrees and that means full throttle, full rated load operation during bulk charging. If the engine is bigger than the load you're just dumping fuel into cubic inches with a higher volume pumping cycle, and wasting it.
As soon as the bulk charging is done and the engine has to back down because the load no longer requires the power, you're already off the peak of it's efficiency curve. Cylinder head temp drops, thermal efficiency drops, volumetric efficiency falls on its face - but electrical efficiency improves.
These engines are designed from ground up, with ignition timing and cam profile and timing to run at 3,600 rpm, not 3,000 or 2,500.
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Chris -
Re: 48VDC generator head
And your reference data is?ChrisOlson wrote: »The GX200 is a more fuel efficient engine - it's BSFC is .51 lb/hp.h compared to the GX240 at .70 lb/hp.h -
Re: 48VDC generator headAnd your reference data is?
The owner's manual for the engines. Honda publishes the dyno data in there.
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Chris -
Re: 48VDC generator headThe generator head is small. Sure you're not going to cook it?
I've talked to three different vendors of these Delco 10SI alternators today. The 10SI/12SI is a pretty durable unit for the most part. But these guys all put either a donut mag claw pole rotor, or a bar mag radial rotor in them, paint them pretty blue or green or red, and strap names to them like "Renegade", "Super Core", and even one called the "Hurricane Cat 4 Mark 1".
For pete's sake - it's just a frickin' Delco with the field coil ripped out and replaced with magnets. :roll:
Not a single one of them know what the heck is going on. Can't get a straight answer out of any of 'em except Wind Blew that they used a standard GM 24 volt stator in that "DC-520". Well, I know what that stator is and their output numbers that you posted in your graph there are highly suspect and faked. Because the voltage curve does not look like that at all from a permanent magnet generator.
If one of them can't demonstrate to me that they know where the bear defecates in the woods I'll just order a magnet from Applied Magnets and build my own so I know what I got.
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Chris -
Re: 48VDC generator head
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Re: 48VDC generator head
Current Manuals From Honda's website for the various engine families:
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Re: 48VDC generator head
If you buy one of the newer RT or UT2 engines, this is what you'll get (unfortunately, they are on the north side of $700 w/electric start):
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Re: 48VDC generator headIf you buy one of the newer RT or UT2 engines, this is what you'll get (unfortunately, they are on the north side of $700 w/electric start)
Northern Tool over in Forest Lake, MN has GX200's brand new for only $359 and they have an aftermarket kit to put electric start on them for $99. If the genset was to be auto-start I'd put electric start on it. But I'm building mine with the good old rope pull with auto-shutdown controlled by the Classic.
For some reason our local Honda dealer don't have any engines in stock - they only order them when somebody wants one.
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Chris -
Re: 48VDC generator head
Uh oh, just noticed an error in the last GX240 specs I posted. The displacement indicates GX270 (4mm larger bore). Honda is getting sloppy. -
Re: 48VDC generator head
One of my neighbors about 5 miles away has a small engine shop and he's into go-kart racing so he has a dyno. I do a lot of machine work for him on crankshafts and cylinder boring so he helps me out when I need something.
We took a GX160 off a cement trowel and ran it on the dyno this morning. On the first run it produced 7.6 lb-ft torque at 3560 rpm, or 5.15 hp. We ran it for 20 minutes under load to get it good and hot and did another dyno pull with it. On the second run it produced 7.8 lb-ft torque @ 3600, or 5.35 hp. Peak torque was 8.0 lb-ft @ 2440 rpm, or 3.72 hp @ peak torque rise.
A GX160 will power a 3.0 KW DC genset with no problem at all if you have a generator that's >90% power efficient.
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Chris -
Re: 48VDC generator head
If you decided on using the GX200 or GX160 and pondering an electronic governor, just look for an EU3000is (GX200) carb and fab your own controller & pickup. The motor is a Mitsubishi MP24S 9Y30 R (8vdc).
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Re: 48VDC generator head
I might use a GX160. My neighbor is going to get hold of a GX200 so we can run that on the dyno and see what it's got. He said the GX200 has always been a "6.5" and the GX160 a "5.5". The dyno numbers we got on the GX160 seem to bear that out because it most definitely has more than 4.8 hp, even with the engine not fully warmed up. Honda has the GX160 as a 4.8 and the GX200 as a 5.5. But they went to a different net rating system. So the only thing that's reliable is actual dyno numbers.
But it will be one or the other. And that carb with the stepper motor already on it looks interesting.
Kind of interesting - they use a 5 horse Briggs block for go-kart racing. He's got a couple of those there that he has $7,000 in the engine. They are fuel injected, 14.5:1 compression on methanol, stroker crank with a short forged rod, roller cams, and they make around 36 hp @ 14,000 rpm! I built two stroker cranks for him for those engines out of 4130 CRM billets but I've never seen one of those engines run. I guess they're pretty wild and they idle at 5,000 rpm, and you have to spin it at 3,000 rpm to get it to start
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Chris -
Re: 48VDC generator head
Well, kind of an old thread now. But I just now got around to working on my DC generator project. I got a GX160 engine for it instead of a GX200. The biggest problem was the generator and I just solved that. I got my wind turbine project done that I was working on before the Christmas holiday. When I took this turbine off the tower and replaced it with the new one I have a big axial generator to use for my DC genset:
That generator weighs 80 lbs and it produces 160 open DC volts @ 1,500 rpm. It is 93.7% power efficient at 150 VDC "clamped" and 20 amps output. The Honda GX160 will drive this thing with ease with a 2.4:1 belt reduction drive @ 3 kW output fed into a Classic 150.
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Chris -
Re: 48VDC generator head
I like your project. I've thought about doing something similar, except I'm not experienced like you in building PMA's, so I would have looked at buying a finished PMA. I was looking for a small diesel engine (something like a Yanmar L70) that I thought would be nice to run at a reduced speed of around 2,400 - 3,000 RPM for better fuel economy and engine longevity. At this point, I don't plan to do anything as I really don't have a need for it, since I'm on-grid.
Another thing I ran across when I was researching a DC charger was the Alphagen DCX 3000. It's basically a Honda EU3000 inverter generator set up for DC only output. Fuel efficiency looks amazing at lower loads since it has variable RPM, but the downside is that it's not really designed to be a charger but rather a "power supply" that provides a constant 52.5VDC output. That's not going to work well for bulk charging batteries. Anyway, there was a brand new one on eBay a while back for around $1000. Here's the specs on this: http://www.alpha.com/outside-plant-power/generators/item/alphagen-dcx-3000
Do you plan to run your GX160 (or GX200) at 3,600 RPM or at a lower RPM? -
Re: 48VDC generator head
I'll set it up for 3,600 rpm @ 3 kW output. With the generator at 93.7% efficiency, a v-belt drive at ~95% efficient, and losses in the wiring and rectifier, I expect it will require close to the full rated flywheel hp of the GX160 @ 3 kW output.
Running an engine at lower than rated speed does not always mean better efficiency. It can mean reduced fuel consumption but the name of the game is kWh/gallon of fuel burned, and output (flywheel hp) drops with reduced engine speed as well. Typically maximum power per gallon of fuel is achieved at rated speed, not reduced speed.
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Chris -
Re: 48VDC generator head
Good point. Honda probably designed the engine to have peak efficiency at the rated engine speed of 3,600 RPM.
Do you anticipate any overheating problems with the PMA since it won't be operating in the wind? Any plans for some forced air cooling of the PMA? -
Re: 48VDC generator headkeyturbocars wrote: »Do you anticipate any overheating problems with the PMA since it won't be operating in the wind? Any plans for some forced air cooling of the PMA?
None. The generator is already fan cooled. The generator rotors double as centrifugal fans. They draw air in the center and discharge it all around the perimeter. But it won't need it anyway on this application. That generator is so heavy duty that 20 amps output won't even get it warm to the touch. On the wind turbine it runs at 1,000 rpm and delivers 43 amps continuous @ 100 volts, and 55 amps @ 50% duty cycle. At 3 kW output it's not even operating at 50% of it's maximum continuous capacity.
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Chris -
Re: 48VDC generator head
Yes, but that doesn't mean mean you are stuck at the rated RPM recommendations. A few minor modes is all it takes to alter it just about anywhere you wish, but the problem then becomes sufficient horsepower for a given displacement. So the easiest path to see 3kW @ 1800-2200 RPM, is increased displacement - preferably more stroke. Fact is, the larger displacement engine can actually be more efficient, using less fuel at the lower RPM than the smaller screamer at rated 3600.keyturbocars wrote: »Good point. Honda probably designed the engine to have peak efficiency at the rated engine speed of 3,600 RPM.
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