90VDC motor, ideas for making turbines

[Jon Miller]

I have got myself 4 of these lovely PM motors they where made in 'Spring Vally, ILL USA' so have come a long way for me, they are brand new and are in great condition and as you can gess I want to make a turbine out of each of them in some sort of batch production to reduce time to build them.  I have all the ideas and plans I need except the blades so I need some help, I want to make plastic blades out of pipe but Im not sure how, 12 volts which is what i want fout of them turns up around 200rpm and hopefully i would like to get this at a rellie slow wind speed so i was thinking 6 blades with diameter of 1 meter or somthing like that.

Any ideas and thoughts welcomed and please do comment lol

Pictures:

There is some sort of size comparision

theres three of the four I have

Thanks

Jonathan www.Otherpower.co.uk

[DanB]

Hi John - neat motors!  I expect the volt/rpm is within reason - maybe a bit slow for 12V.

I think the big problem will be the 1.35 amp part, I doubt you can get much current from them - I expect their resistance is high.

[Jon Miller]

No supprises there yep bit high around 35 ohms but I still reckon there worth the effot.  Thanks Dan B

[nothing to lose]

Why do you want to limit them to only 12V? If they put out more volts the batteries will hold the volts down till charged. How did you test for that 12V, was it open volts with no load?

"I want to make plastic blades out of pipe but Im not sure how, 12 volts which is what i want fout of them turns up around 200rpm and hopefully i would like to get this at a rellie slow wind speed so i was thinking 6 blades "

Look for Zubbly-woofer blades on this site, they work well. You probably want 3 blades not 6 though. With a set of Zubbly blades you would have 4, or as I did cut them at the center hub and get 4 seperate blades then mount 3 to a hub.

I think the faster the motor turns the more power you will get, it may show to be 50volts or so but the battery bank will hold it down to 12V durring charging. Volts may climb after full charge, but you should have a dumpload or such for any wind gennie unless you plan to watch it and manaully shut it down when full charged. So higher volts will not hurt anything.

At 90volt and 1.35 amps that would be 121.5 watts if spun at full speed of 1375rpm I think. Charging 12V batteries then it should be about 10amps. 200rpm is about 1/7 of the speed so figure probably about 1/7 of the amps, 10/7 = 1.42amps and at 12V that would be 17watts.

I think the above is pretty close to correct though maybe not perfect.

You don't actaully say if you have a certain limit to what you can do there. Myself I think for these motors I would try using a medium large 3 blade rotor (maybe 6') to drive a pully and gear up the motors to spin faster. Mount all 4 motors to run off one set of blades using only one belt. Something similar to a riding lawn mowers cutting deck where you have 1 drive pulley/belt and 3 or 4 pullies for the mower blades. I think if you built it like that you may get nearer 400-500watts from the 4 motors using 1 set of blades.

Or use 2 motors on a set of blades and build two units.

 Just mounting blades directly on the motors I don't think you will get the full output they could give if geared up though.

[Jon Miller]

The last idea sounds a bit to complicated for my liking, im tempted to make wooden blades aswell, I reckon ill have a little play with some batterys and my lathe to see wots wot with them, ill have to do some tests cause the comments you made are wot i was thinking but ill have a play first maybe tonite and re post wot i found.  thanks  for that nothing to loss gd thoughts

[richhagen]

Jon, these are my thoughts, some of which may not be correct on the subject.  I'm also tired at the moment, so double check any math.

I use a little rule of thumb to approximate although in practice the

output varies a bit with the specific motor.

rated rpm divided by rated voltage multiplied by the desired cut in voltage,

multiplied by 1.1.

for your motor,

1375 rpm at 90VDC, approximation of 1375/90*12*1.1=201rpm

So it would seem to me that 200 rpm at 12 volt charging is pretty reasonable.  

You are not going to get much current at all from that motor however.  

The 60 plus ohms of resistance would scare me a little.  When you are holding the voltage at 12 volts,

and if you don't have much line resistance, it seems to me that the motor will heat as in most of the resistance will be in the winding if it doesn't completely saturate the laminates, which would in a way protect it by limiting the power.  I would use smaller guage connecting wire or a resistor in series to let the output voltage of the motor go up a bit during gusty periods.  

It seems to me that you could get more power with a higher TSR blade and a higher battery voltage because of that internal resistance.

I have a little 180 volt motor that appears to be of similar design, I never made a mill out of it because I felt it was

too hard to start turning by hand compared to other motors I had due to the brushes, and the windings were too thin.  It

is .45 amps at 180 volts.

In 3 feet diameter of airspace at 10MPH windspeed there should be about 36.66 watts of total power.  If your blades can capture 35% of that at that air speed then that would yeild about 12.83 watts.  

50MPH*(5280ft/mi)(60min/hr)(pi*3foot) = 466rpm

A tsr of 5 would yield 466rpm at that windspeed for a 3 foot diameter blade set.

A 3 foot diameter TSR 5 blade set should be able to get some power out at 10MPH windspeed I would think, It might over power the motor by a bit, and would run slower than its designed tip speed ratio but would probably work.  You would likely overspeed and wouldn't get much more power in high winds though.

I suspect you will get some power, but not much even in high winds at 12V.  

Best of luck with your project.  Rich Hagen (about 85 miles from Spring Valley)

[CG]

Jon,

You are in the UK and you have seen my postings on gutter blades, you will not find a cheaper or easier way to make small turbine blades than using PVC guttering from B&Q. I have just made some new blades from the Deep Flow brand of guttering and when I can get my hands on my neighbour's digital camera and some of his time I will make a posting. Deep flow is a bit wider than standard guttering so I went up to .75 metres with a two blader. But I used my standard rig to put the rotor on and it ended in disaster in high winds, I think the blade clipped the mast. The whole getup was lifted off the mast and one blade was broken. this all happened overnight so I am not sure what really happened.

At the moment I have a six blader up using my narrow .5 metre blades from standard pvc guttering, that is working fine in today's cold easterlies. This would probably do you fine for what you want. Forget plastic pipe for small turbines we don't need to use that here in the UK; if PVC guttering was as easy to get in the USA as it is here I would have never made my posting because they would have been using it there for small turbines years ago.

You're a lucky devil getting those small PMAs.

All the best with your project.