Carrying on from the 'sick and tired' thread can we discuss this?

Looking at a 6KVA Alternator in Machine Mart it gives 230v AC

I know that alternators create drag and sap power but how much?

What size engine would power this at 3Krpm and what size motor would it power?

EG: would my 100cc lawnmower engine turn it at a consistent speed to run a motor and keep some battery's charged?

I know trains use it because they could not develop and strong enough transmission for direct drive for the massive 3000hp engines.

So, question is how big an engine based on it running @ 3K to give enough for a decent size leccy motor?

Is it feasable or dead in the water?
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Simplifying matters slightly, 6kVA is about 8hp, so allowing for efficiency you'd probably want about a 10hp engine to drive it if you want to get the most out of it, so your 100cc B&S mower engine won't be up to the job. On the output side the 6kVA alternator would drive a motor something a bit under 6kW allowing for efficiency/pf.

Not sure what the application is - why dont you just get a genny? Maybe I should read that other thread...

Liam

Personally I think a diesel generator governed to run at a constant speed for fuel efficiency that then directly drives an electric motor would be the most cost effective. No gearbox, clutch etc just some heavy amp cable and a switch to change polarity for reverse. As you say Deisel/electric trains use just this method and I'm surprised no car maker has went this route as it seems the cheapest of all.

I think youre looking at it the wrong way.

Why do you want a 230V alternator? - Would a 12V alternator and motors not be better? Theres no inverters or rectifiers needed this way.

The load of the motor would increase the strain on the alternator and subsequently the engine.

Look up Diesel Rotary UPS systems, and get some more ideas from there.

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Originally posted by MakeEverything
I think youre looking at it the wrong way.

Why do you want a 230V alternator? - Would a 12V alternator and motors not be better? Theres no inverters or rectifiers needed this way.

The load of the motor would increase the strain on the alternator and subsequently the engine.

Look up Diesel Rotary UPS systems, and get some more ideas from there.

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quote:

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Originally posted by MakeEverything
I think youre looking at it the wrong way.

Why do you want a 230V alternator? - Would a 12V alternator and motors not be better? Theres no inverters or rectifiers needed this way.

The load of the motor would increase the strain on the alternator and subsequently the engine.

Look up Diesel Rotary UPS systems, and get some more ideas from there.

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Not helpful in the slightest, but Jaguar are doing a similar thing...

http://www.carsuk.net/jaguar-hybrid-confirmed/

They're supposedly using a 1.2 3-cyl engine to power an alternator which charges batteries, and the system can provide quite a bit of power (i think they said near the 300bhp mark!) for short bursts of a minute or so. Clever stuff!

6kW is 8.042 BHP. 6kVA is the output. Its efficiency could be anywhere between 80% and 95% depending on its design and the magnets used. So assume 8.5 to 10 BHP needed to turn the motor at the rated speed at full electrical power. Your engine will need to make 10 BHP at the required revs or it will slow down at full electrical load. Small bike engines will make 10 BHP but at more like 7000 or 10000 RPM, not the 3000 RPM of your motor. You'd be better off with a small diesel.

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Originally posted by phelpsa
Not helpful in the slightest, but Jaguar are doing a similar thing...

http://www.carsuk.net/jaguar-hybrid-confirmed/

They're supposedly using a 1.2 3-cyl engine to power an alternator which charges batteries, and the system can provide quite a bit of power (i think they said near the 300bhp mark!) for short bursts of a minute or so. Clever stuff!

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I think the hard/expensive bit will be the controller for how fast you make the motor go, you could'nt just have it wired to the generator with just a switch for neutral & direction as you'd get a response like dumping the clutch at full throttle on a conventional engine & drivetrain.
I dont know how the controller works but I might be going to find out as I work for a dealer for these: http://www.polarisindustries.com/en-us/ATV-RANGER/2010/Mid-Size-Utility-Vehicles/RANGER-EV/Pages/Overview.aspx
As for the volts, the higher the better from an efficiency point of view, the higher the voltage the lighter the wires & switches etc can be for the same power, or more power through the same size connections.

a diesel engine driving a CVT would be much simpler and cheaper.

the only reasons trains use the electric system is to have more driven wheels to give better grip, and the issue of transferring 3000hp.....

heres a nice package :



will

quote:

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Originally posted by phelpsa
http://www.carsuk.net/jaguar-hybrid-confirmed/
They're supposedly using a 1.2 3-cyl engine to power an alternator which charges batteries,

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Saying that, it seems to be quite public:

Jets



ATB

Simon

think about the efficiancy of the motor too. electric motors are generally quite efficiant, but get less efficiant with heat, so if you putting an engine next to it, it will just add to heat and therefore resistance...

you could try on a smaller scale like a go-kart... i wouldnt go full scale strait away, just incase it majorly fails

good luck though, hope it does work

quote:

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Originally posted by Simon

quote:

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Originally posted by phelpsa
http://www.carsuk.net/jaguar-hybrid-confirmed/
They're supposedly using a 1.2 3-cyl engine to power an alternator which charges batteries,

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I know Jag are interested in stuff more interesting than that, though I can't say anymore

ATB

Simon

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I have to say, top gear was actually nearly spot on with their boxy car a while back when they got a diesel genny. That is to say the genny runs at constant speed and is so always operating at peak efficiency. Even with electrical losses that should give good efficiency overall.