power tests (21" stator genni)

[marv]

Hi All,   I finally found a way to test this monster and here are some results.

This is a front driveshaft from a 4x4. It's nice and short,it worked well.

 First some background info;  12pole,  36 coil,  72 slot,  3 phase,  24 mags,

 2x2"x1/2" neo's, 100 turns #18 wire, silicon laminations. I think that covers that.

      This is how the tests were conducted.

      4mm air gap, rectified DC and with a 50 ohm load.  (DELTA)

        Results:

        52 rpm------100V-----------1.76amp---------176watt

        132 rpm------200V-----------4.8 amp---------960watt

        225 rpm------500V-----------8.  amp--------4000watt  

I was planning on a 5.5-6 meter (18-20 feet) prop 3 blade tip/speed ratio 7

230 rpm top speed.

I would welcome (most) any sugestions or comments.

 Marv.      

[monte350c]

Hi Marv,

Wow - pretty impressive results, I'd say you deserve a pat on the back for this one. I've been following your project since you first posted it here.

The high voltage and low amps should cut down the amount of heat generated in the stator. Also it should be pretty efficient over a longish run of wire. At 225 rpm that should work out to about 22.5 HZ (provided my brain is operating correctly!)

Just out of curiosity have you worked out what you're going to do downstream of this alternator - transforming, storing, or using it as you go?

That constant speed mechanism for the prop is looking pretty nice too!

Ted.

[tecker]

  What kind of torque are you looking at for> 500 volts  

[Dan M]

Marv,

I'd love to see what you're thinking as far as blades (material, profile, etc.)

Also, I don't know what you're thinking about to tap this power, but the relatively high voltage sould work well to generate heat through a resistive element like a hot water heater element.

-Dan M

[hvirtane]

A nice test bench!

I think that your results

are quite impressive.

Could you please publish a bit more

about the design of the alt.

How much you put silicon

steel laminates on that

and which way are they arranged.

I'm interested in seeing

your design for the blades.

- Hannu

[marv]

Ted; I want to charge a 48v battery system but I'm not sure if I have to use a

transformer or the batteries would pull it down to 48v. Anyone have a suggestion?

Tecker; I didn't test the torque at 500v but I checked it for startup. 16 foot lbs.

with a torque wrench.

Hannu; The design of this genni is mostly in my past posts with pictures.

thanks Marv

[monte350c]

Hi Hannu,

(Hope you don't mind Marv, I took the liberty of posting the links to your old posts!)

I too have been following Marv's progress - here are a few links to this genny:

http://www.fieldlines.com/story/2003/11/8/182745/040

(I guess Marv is NOT afraid of heights!)

http://www.fieldlines.com/story/2003/12/23/194340/89

http://www.fieldlines.com/story/2004/2/22/74839/0881

http://www.fieldlines.com/story/2004/3/14/184039/727

http://www.fieldlines.com/story/2004/4/4/182228/0691

This thing should put out some very serious power....

Ted.

[hvirtane]

Hi,

thanks Ted.

I looked through all the posts.

It looks really nice.

I got the information

about the alternator.

It is something quite similar

I have been suggesting for

my Indian friend to do next.

A really beautiful tower.

I had seen the picture

but didn't remember that it

was for the same project.

I will show the picture of your tower

to my friends here in Finland.

With the other of them we are

reinstalling a 15 kW turbine on the

top of a 32 m tower. We have now 20 m

of that tower up. We hope to get

the mill up during this summer while

Kyosti is on his holidays.

- Hannu

[KHB1]

Marv it's one marv(elus) machine I cant wait to see it on top of that tower.

KHB1 cecil

[Michael]

nice job,

your load was 50 ohms, what was the resistance of your source, what was the resistance of each phase?

did you calculate the power lost in the coils?

P = I^2 x R,  R = resistance of your coils.

Great output for only 24 magnets!, did you have any cogging?

i would suggest that you use lock-nuts, or put "lock-tight" on your nuts if you havent done already, as the vibrations may loosen them over time.

Michael.

[marv]

Hi Michael;   The resistance of each phase is 7.7 ohms x3=23.1 ohms total.

The cogging at 4mm air gap isn't that bad considering the size of this. I checked

cogging with a torque wrench for startup and got 16 foot pounds. But with 18-20'

dia. blades that should be ok.

I like the design of your blades using the skeleton, expandable foam, glass wrap

method. Did they hold together for you? Or any upgrades to suggest?

Marv.

[Michael]

If each phase is 7.7 ohms, then if it is connected in delta shouldn't the source resistance be 7.7 / 3 = 2.5 ohms?

If the source is 2.5 ohms, then your machine is running at 95% efficiency, now that's impressive.

Cogging torque seems too high for a 2-bladed machine, hopefully 3 blades should be ok

5 blades would be even better,

how many blades to u plan on using?

I recommend for 18-20' blades you make them using fibreglass and carbon fibre, my 10kw blades are lager than Dans latest turbine, and are very very light and strong, i think wood is good for smaller turbines because of the weight problem.

The metal skeleton has no strength, it is strong enough to hold the foam in place,

the strength comes from the fibreglass and carbon fibre, make sure you use plenty of fibreglass at the root and fibreglass all blades together to make 1-piece, you dont want these one of these huge blade coming loose and flying off.

I haven't put the blades up yet, i haven't had time to finish the tower, been too busy with the 1.8 metre turbine and a new much larger turbine,

as for strength, the 1.8 metre is still holding together even after it hit the heavy copper power cord at 2365RPM, carbon fibre with vinyl ester resin makes very tough blades.

Michael.

[Nando]

BEAUTIFUL PIECE OF EQUIPMENT -- CONGRATULATIONS

Your generator is a low frequency unit, for 50 Hz the RPM is 500, so at 225 RPM the output frequency is 22.5 Hz and of course lower frequency ( 5.2 Hz) at lower 52 RPM.

No way to use transformers to bring the power down economically.

You need to rectify and do a DC/AC or DC/DC conversion to a workable voltage.

You could have a dual conversion ( with MPPT), from low voltage to 700 volts and from there a DC/AC or A DC/DC converter.

Conversion depends on what you want to do.

You say 48 volts battery bank -- what size -- amp-hour

The DC/DC converter could be a full bridge IGBT with PWM for a good charging battery profile.

The problem is the availability of the 5 to 6 KW DC/DC or the DC/AC converters.

A high voltage Buck down converter is, as well, possible -- it is a major effort to do, because the major ratio is 700/57 volts = 8.77 ratio that at this power needs to be handled carefully for MPPT capabilities.

Regards

Nando