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Forum Index : Windmills : 2HP Motor Conversion
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Bryan1 Guru  Joined: 22/02/2006 Location: AustraliaPosts: 1462 |
G'day guys,, That last pic I put up shows the top of the motor and the connection are on the other side. I fount the centre tap and brought the other 3 wires out so I could try star and delta. Anyway I did the lathe test in my toolroom lathe which is only 1/2hp and I used 2 12 volt batteries in series for testing for 24 volts. I preset the vfd and lathe to go between 50 and 240 rpm in the back gear, the batteires were initially sitting on 23.2 volts. testing in star 50 rpm 25.2 volts 1.8 amps 100rpm 27.1 volts 6.0 amps 150rpm 29.6 volts 8.9 amps after 150rpm the lathe got bogged down and wouldn't go any faster. As the battery voltage shows the batteries arent in the best shape but it does prove this is one powerfull little genny. I'm pretty sure my 3 metre bladeset will overcome the cogging issue and I'm going to make the tail very light so it will furl early as with the windings in the motor I reckon 15-20 amps will be tops before it burns out. If I'm wrong here please chime in. It goingto be a big job befoe this genny flies as I'm re-doing my 3 metre blades with fiberglass coth exopyed in on the leading edge and converting the blade mount to suit my dual tapered lock coupling. One thing I did notice in the cad drawing it shows the gap in the coils in the wide gap as approx 2-1/2 slots. In that pic above i put some black texta marks on each pole and where the wide gap at about the 5 o'clock position is theres only 2 slots gap maximin. This could be where the problem lies, going for imperial instead of metric mags. Cheers Bryan |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
This one looks like a candidate for a VAWT, or a rewire for a HAWT, or a serious size rotor for your 24V setup. The 50W @ 50rpm would probably be unachievable on a 3m rotor, may need to be larger, or like a southern cross pumper type, or go for a higher voltage battery. I am sure you can make it work. Gordon. become more energy aware |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Just a reminder that everyone needs to be careful what they say on a forum. Any sort of threat against someone else, even if in fun, can be taken the wrong way by the intended recipient, other forum members, or guests. A post on a internet forum has as much legal standing as a post in a newpaper or other types of media. Also, if something has got you fired up, its always a good idea to let yourself cool down and think about it before posting a message here. This is not a place to vent, its a place to share idea's. Not all idea's are guarenteed to work. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5119 |
Repost of missing posts. Dinges wrote..... After some more thinking I can only see 3 possible problems: 1). The calculated angles of the poles are incorrect. I'm 100% sure they're correct though. 2). Machining errors. Something may have gone wrong during the machining phase that caused the angles to differ from the theoretically determined ones. Obviously this is hard (and, by now, after casting in resin, impossible) to check, but could have been measured with the proper equipment (3D measuring machine) 3). This method (offsetting) only works with alternating poles (N-S-N-S-N-S-N-S), not with conversions where two magnets make up one pole (N-N-S-S-N-N-S-S). It may be a case of non-linearities of the sums of the magnetic fields of the discrete magnets. As I said originally: [quote=Dinges]I don't think it'd cog, I'd be 100% certain it wouldn't if you'd mount the magnets N-S-N-S... (i.e. 8-pole)... but I've never actually verified this configuration (N-N-S-S-N-N...) myself yet. I'm reasonably sure it wouldn't cog though...but no guarantees, of course.[/quote] http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?T ID=1390&PN=1&TPN=2 Whether this is the problem could be checked for by simulating in FEMM by someone who has the time and inclination to do this. Currently my money is on either nr.2 or nr. 3. As to 2), I can't verify it's not a case of something having gone wrong during machining and will have to take your word for it that the angles are correct. As to 3), I'm not going to spend more time and effort on simulating for cogging to verify this. My time is currently better spent doing other things. Unless someone else expends some effort on this issue, I guess we'll never know.... Herb may be right too with his remark on felt torque-ripple when wired in delta, or Janne with his remark about the broken magnet having lost strength somehow. I'm not an expert in this topic, just stumbling along and trying to learn myself. One thing I *do* know, however, is that I don't appreciate being talked to as you did in a previous post. I expect it not to happen again. Peter. KiwiJohn wrote..... Peter, I am a Kiwi, which means we have the Aussies as neighbours and I have spent some time there. Knowing their culture I would not be too upset at the Vaseline remark. Just my two bits. Janne wrote..... I got bored and made 2 FEMM simulations on the motor. The first one is of the current situation, with each magnet being 43.75 degrees apart. The second one is with the magnets on same pole being tightly together, and the offset angle calculated with formula published in Peter's "decogging tutorial", in this case 360/(36*4)=2.5(so the second pole is at 87.5 degrees relative to the 1st one). To me at least the second case looks cog-free, but i'm not 100% sure about the first one(too tired to think clearly?) I'll add them as links as not to strecth the page too wide. how it looks now: http://img25.imageshack.us/my.php?image=oldway.jpg the other method: http://img25.imageshack.us/my.php?image=newway.jpg Dinges wrote..... Janne, If you want to try to simulate the cogging in FEMM, you'll need a LUA script that simulates the cogging torque as the rotor rotates. Just two plots give no information in this case. The LUA script below probably works, it's what I've used in the past. Obviously you need to change the names of some files and directories. When you make the FEMM model (importing the CAD model), make sure that the center of the rotor (axis of rotation) is at (x,y)=(0,0). Also, you'll have to manually define a 'group' (nr.1) consisting of the steel rotor and the magnets on it. It is this 'group' that will be rotated in 0.1 deg steps. Keep in mind that you'll need a pretty fine mesh too... so it will take a lot of computation time. If the mesh is too coarse, calculation noise will drown out the cogging effect you are looking for. Once the simulation run is finished you'll end up with a file called 'cog.txt'. This contains the cogging torque values. You can import this into a spreadsheet and then plot it, showing you variations in torque for various angular positions. The smaller the variations, the better. You'd need to do two runs: one as an 8 pole, and another one as a 4 pole (with 2 magnets per pole, but otherwise exactly the same model/drawing), and then compare the cogging results for the two to see if there is a difference. I'd modify the script a little, you don't need to simulate over the full 360 degrees, 10 degrees is more than enough (one slot). Or make it 15 degrees. Peter. Janne wrote..... Hi Peter, and thanks for the help with the scripts. I left the computer doing the math for the night, and according to the results both conversions should be perfectly cog free(with a maxium of ~4Nmm of cogging torque on the 30 degree sample of travel). Both simulation was run with each magnet being 43.75 degrees apart from each other. The 2 files i uploaded are actually .txt files, but because this damn Forum doesn't allow uploading txt files i renamed them to .pdf, so anyone wanting to peek at them must first rename them back to .txt 2009-03-18_155841_4polecog.pdf2009-03-18_155851_8polecog.pdf Sorry Janne, I've lost those files, could you repost? Glenn kumtarest wrote..... hi Bryan 1. i dont know if this will help you but i did the same as you in a car alternator and i set the magnets up the same way running straight up and down the armature with a 1.5 mm air gap and when i put it together i could not believe the amount of cogging i had .i tested it on a lathe and within 1 minute it got red hot and very little power .i then did a lot of research and then i set the magnets up on an angle not straight up and down i then set 1 magnet gap different to the others so that it would not stop in the same place .i then set it up with 1.5 mm air gap nothing different was done except some machining to get the correct gap to suit the angles. when i put it together i could not believe the difference you could turn it by hand very easy and when i tested it on a test bench i let it run for for 10 minutes at a good speed and it didnt even get warm and produced a lot of poweri hope this helps you regards kumtarest The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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