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Forum Index : Windmills : T plate failure
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Highlander Senior Member  Joined: 03/10/2006 Location: AustraliaPosts: 266 |
G'day all, well the T plates were a complete failure. Start cogg was 675ml, same as 7 phase 1 line of neo Running cogg 550ml, 205ml increase What was really disappointing, was power was way down to 6 amps from the previous 20. I used 1 line of neo's I checked each phase separately, wiring ok I have given up on this, and given up on extracting more than 300 watts out of one that doesn't cogg so much that it won't start in light to moderate winds. I think building a second mill is an easier and better option.  Central Victorian highlands |
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| KiwiJohn Guru  Joined: 01/12/2005 Location: New ZealandPosts: 691 |
I am sort of not suprised that the T plates did not work but I am pleased you gave it a go, full marks for effort I think and have a cold one on me.  |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah its a shame it didn't work as well as hoped, but it was worth the effort. Its the failures that you learn by. Sounds like it reduced cogging, but also lost power. Maybe this was due to the material used, I think the steel used in laminations has a lot of silicon in it to stop it becoming easily magnetised, meaning it can change its magnet flux easily and quickly. Mild steel tends to become magnetised, so requires more effort before it changes its magnet flux. So the mild steel caps on the poles would have the effect of reducing the intensity of the magnet flux changes as the magnets went past. Maybe. Just a theory. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Another thing that may have contributed is the "glue". If there was any gap or discontinuity between the two lots of metal, it will have a dramatic (and negative) effect on the field through/around the coils and thus output. |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
G'day Ross, I didn't end up using the glue as the screws were holding so well. I showed it to a mechanical engineer today, and he confused me with all the equations required to design a motor/altenator properly. His input was that the gap was too small, but field should be tested to determine the correct gap. He said as a rule of thumb if the magnets don't repel each other that's about right. His brother is an electrical engineer and said to take some photo's and he'll pass them on for his advice. Central Victorian highlands |
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Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
Congratulations Highlander on the sterling effort, and sorry that I led you to do all that work - even more sorry that it led to nought. I guess that the gap between adjacent plates was too small after all. If the plates did not seat really close over the pole pieces, there would be an increasein air gap and consequent loss of working magnetic field. Gizmo's idfea could well be right too. What did you use for the rotor please? The increased diameter of the stator should have meant a larger diameter rotor would be needed. I have not got my mind across why it had a reduced starting cog and an increased running cog yet. Megawatt Man |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
Hi Megawatt, no big deal. I'm the sort of person that likes to try rather than wonder about possibilities. The rotor was the F&P one with the ferrites taken out and 3mm thick neo's put in place. I know the spacing was perfect as it came from a computor generated template. One other thing, it makes an extrodinary clicky whining noise, nothing is scraping. I coloured the plates with texta and there's no scrape marks, it must be to do with the field. The mech engineer said the fields were overlapping and causing loss, I'm waiting on his brother(elec engineer) for more detail, so all may not be lost, but I'm not getting my hopes up. 
The plates were held really snug against the poles, so no prob there but I think Glenn's silicon steel idea is very plausable. Central Victorian highlands |
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| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
G'day Hoghlander, I reckon the idea of the fields "overlapping" is close to the mark. I don't think its actually overlapping ( hence the " "), rather that when the gap between the Ts is fine, it's too easy for the magnetic field to bridge the gap and not get down and dirty where the coils are. There's probably an empirical rule that says something like the gap betwen adjacent pole pieces should be twice (or thrice?) the gap between the rotor and stator. Maybe I shouldn't have been so agreeable about the fine gap between pole pieces. Is it feasible to widen them at this stage? It they are 1mm, a 2mm gap should give a performance that's measurably different and of value to the overall effort. The bugger might be that a 2 mm gap would look promising so a 3 mm gap would look good to try. What I find of interest abd challenge is that the cog was the same aa a 7 phase unit, even though neos were used. That means there was a significant reducytion in cog over the standard. Now about ultimate capacities. Gizmo is currently putting together a set of equations (or rather he's asking us all to give of our best in that matter). WE really need to know (and I mean know) what magnetic fux saturates the core. Then we cxan actually calculate how many neos or other magnets are needed to get us just up to that point. Then we have the magnetics out of contention. More later Megawatt Man |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Question: is anyone set up to run a ramp generator into an electromagnet and measure the output voltage from an F&P coil, displaying current on one axis and voltage on the other in X-Y mode? This should draw a nearly straight line with a big kink in it where we reach "saturation" of the core. It should be reasonably easy to then determine the ampere-turns at that point and hopefully deduce/calculate the actual magnetic field. I have all the bits here to do it, but really don't have the time - but if it's that important, and nobody else can, I'll try to make time, somewhere (not this week, I'm about to head off to Sydney for a few days). RossW |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
The plates are just screwed on so if req'd it would be easy to take them off and grind them a bit. About saturation, another website states the core saturates at 600 watts(on their mill) but that same website sells generator/chargers which run off vegetable oil. the output states up to 1000 watts. click here So it's got me buggered 
Note the text said "modified smart drive" The cluey bugger has got one on us Central Victorian highlands |
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| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
OK, a second spray. When we know the maximum value of magnetic flux and we apply neos or whatever gives us the max flux, we then need to determine the optimum speed to generate the right voltage to cause the maximum current for the size wire on the stator poles. Then we will know just what power can be extracted from a F&P. Megawatt Man |
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Pt w/field Matt Senior Member Joined: 24/02/2006 Location: AustraliaPosts: 105 |
hi highlander check out the innovation site again under information getting smart with a smart drive 135kb pfd,a100 series wired for parael will produce 1344watts @12v and thats probly what he is using,but to achieve this you have to spin it at over 1000 rpm which means tooth belt drive 3 to 1 gearing and a big set of blades to provide enougth torque to match the power output.no trickery there,you can also back space the rotor to get it working in the power band to suit your blades if it stalls the blades matt down south |
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| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
See, there's a bit of loose info out there. Is it 600 watts or more? I remember Highlander saying that a pole piece measured 4.5 mm across. What is the other dimension for the width of a pole? When I know that I can have a stab at the max field. I'd better use the word field in future, so when I leave out a letter from flux it doesn't look so bad. Megawatt Man |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Ross, regarding determining saturation flux. I have an arc of a stator that I cut up to reduce the number of poles which may be useful. If I put AC on one coil I should be able to measure AC from the adjacent coil, right? As I increase the current in the first coil the voltage of the second will rise but I should see a dip in the rate of change at saturation. Is that about the guts of this test? Do you have any idea how many amps I might need to do this? Is frequency important, I would likely be using 50Hz but shouldnt we be using the frequency that the alternator would be producing at? Maybe not important? cheers |
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| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
Gday JiwiJohn, I know you didn't ask me but here goes. You could do exactly what you propose, but I reckon you would need to close the magnetic circuit by attaching some magnetic material between the tops of the poles- another pole would do, g clamped on would be enough. An alternative might be to wind a good number of turns over the top of the coil that you'll be passing the current through, so that both excitng coil and measuring coil are linked by the same magnetic field. When you note the current at which the voltgage induced into the measuring coil starts to drop off, what's needed is to know how many amps and how many turns were on theexciting coil. When those two quantities are multiplied togther, we have the saturation magnetising force in Ampere.Turns. Then we need to select neos or oter magnets and an air gap that just allows the neos to magnetise the poles to the max, just short of saturation. Then we can move on to the other variables, they are the more predictable ones. Megawatt Man |
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| KiwiJohn Guru Joined: 01/12/2005 Location: New ZealandPosts: 691 |
Megawatt Man, yes, I was thinking of winding a pick up coil over the one being tested. I am not sure that adding more iron to the circuit is a good idea or not. If I did that how would I know that the core material had reached saturation or just the added metal? Better I think to just use air to complete the magnetic circuit. I have PC data logger that can read up to 30 volts and 8 amps. Of course I can add shunts to read higher values. The software will likely be more of a challenge than any other part of the project! I think I have plenty of current available from a little spot welder and I have an ancient theatrical stage light dimmer rheostat. It wont be too much loss if I cook one coil before I learn to control the amps!  |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
G'day fellas, I used Gills multi measurement and ran it at 750 rpm for 2 min. The plates got so hot I couldn't touch them. Central Victorian highlands |
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| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
G'day again, no it wouldn't matter adding some magnetic material in series, it would if it were in parallel. But the pickup coil over the main exciter coil will be fine. If you have pulled a spider right down, could you please tell me the sideways dimensions of the core? One dimension I think is 4.5 mm, what is the other? If I know that, I can estimate the magnetic flux that would saturate the core, I have some characteristic curves for silicon steel, maybe not for 3.5% though. I could still give an estimate of what the practical test will show, so it could provide a basis for determining test gear capacity. Whoops, I used "flux" again - wish I could type without typos! Megawatt Man |
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| Highlander Senior Member Joined: 03/10/2006 Location: AustraliaPosts: 266 |
Hey Mega I started another thread on saturation, the dimentions are there.  Central Victorian highlands |
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| Megawatt Man Senior Member Joined: 03/05/2006 Location: AustraliaPosts: 119 |
Posted this on Saturation thread, should have been here I think. Re Highlanders later report, about the Ts getting too hot, that's eddy currents and I reckon widening the gaps would reduce it, but I don't know by how much. Maybe the eddy current thing makes it too hard. We need a certain thickness up there to allow a reasonable path for the mag field to get part way across the next pole before leaving the last, via the skew to reduce cogging, but thin enough to discourage eddy. Wider gaps would cause the flux to go down deeper into the poles and I predict would give a better output. I reckon too that since the field would have a better opportunity to do its work on the coils better, it would do a bit less eddy current energy wasting. Megawatt Man |
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