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Forum Index : Windmills : Maxed out at 4amps
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dazler Newbie  Joined: 21/10/2007 Location: AustraliaPosts: 37 |
Hi guys, i am maxing out at 4 amps into a 24v battery bank, but i can clearly hear that its spinning faster and faster past this point? this my set up: 1 x 80 mod 2s 7poles. 2.4m blades. 3 refractors at the mill. 15m power core (240v 10amp) im using 2 wires for + and 1 earth for - . battery's 1x 12v 105ah and 1 x 12v 50 ah to make 24v. so is this set up of the chart  or is the power core not big enough?
thanks daz |
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| dazler Newbie Joined: 21/10/2007 Location: AustraliaPosts: 37 |
also i used a small blade set at 1.4m 5 blade. this set can see 4 amps to but stops here to. i used to have the old 60 f&p, 7s 2poles wired, which got up to 6 amps into 12v bat. using the smaller blades. so i'm unsure what happened? cheers daz |
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| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Nothing to do with the lack of current, but is it a good idea to put a 12V 50 ah battery in series with a 12V 105 ah battery? Seems to me the smaller one is going to be subject to larger discharge. In any case, I thought is was better to use matched batteries. If they didn't cost much then I guess it doesn't really matter. If you short out one end of the power cable and have an Ohmeter that can measure low resistance values I would measure it or go to a reference book, find the Ohms/metre and then work out what the resistance of the connecting cable is. Then work out how much power you are losing. My guess is that it is not the cable. Good luck |
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GWatPE Senior Member  Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Sounds like inductance limiting at work. My F&P 2.4m blade rotor series80 7s2p, twisted poles, behaved the same into a 24V battery. Cap voltage doubler and series caps to 24V and 48V loadings doubled max power and lowered cutin. Gordon. become more energy aware |
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Smart Drives Senior Member Joined: 06/07/2009 Location: AustraliaPosts: 115 |
Have you used loctite to attach the shaft to the bearings ? Smart drive shafts have a habit of not gripping and spinning in the bearings. Cameron. All smart drive parts sold Custom built turbine parts on Multicam flatbed CNC Router |
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| dazler Newbie Joined: 21/10/2007 Location: AustraliaPosts: 37 |
Thanks guys for your help. Gordon, wouldn't it just spin up to whatever amps it made? But it is hitting 4 amps at around about 28 volts(112watts). how some of you guys machines make 250 300 watts or more? Cameron, no I haven't, but it shouldn't matter I thought coz the things would still slip and spin up the stater. cheers |
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| Smart Drives Senior Member Joined: 06/07/2009 Location: AustraliaPosts: 115 |
Thats right but Its just one more hurdle (friction, instead of using greased bearings) the motor has to overcome , i probably should of been more specific sorry. Have you got a close up photo of your re-wire on the motor. Cameron. All smart drive parts sold Custom built turbine parts on Multicam flatbed CNC Router |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi dazler, my F&P has produced 20A into my 24V battery bank, but this was AC coupled with capacitors. This was a while ago when I was confirming results obtained by bryan1 on a 100S wired in delta. I have replicated the performance with a series80 7s2p. Higher power was obtained with additional voltage doublers and additional 48V loadings. In comparison the same windmill configuration, blades/furling/loading with AxFx alternator instead of F&P produces 20A into my 48V battery. [double power output from the same sized unit] The F&P has useful characteristics that assist with management of upper power levels. The alternator automatically power limits. As long as the windmill won't fly to bits with the high rpms that result. Furling should be set to protect in this rpm region. An AxFx mill won't back off at higher power levels. You have to ensure the furling and diversion loadings are adequate. I am rebuilding my F&P alternator and making an aluminium version of my new AxFx design. The iron in the F&P was showing serious corrosion effects after a year. The magnets in the rotor are beginning to crack as moisture and salt gets into the iron laminations behind the magnets. I no longer have a F&P mill, so this phase of my testing is finished. Gordon. become more energy aware |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Cameron , I have noticed you have mentioned this point previously as well , if the spacer between the bearings is the right size and the nut is nipped up on the inner bearing races with no loading on the outer , there should be no problem with bearings spinning or shaft spin . If anything appilying a drop of thread locker to the retaining nut would be the best but not needed as the rotor then locks onto that , if you are after every bit of friction reduction then removing the inner bearing seals and running the bearings in a 50/50 oil grease slurry and use some sealant when installing the bearings into their housings to keep the oil in. I have even removed the lips of the outter seals and had no problems ,but that was before the PVC blades and pole twisting .. If the bearings are getting tight when the nut is tightened then cut some shims to add in to the spacer to reduce the pre load to zero when the retaining nut is tight ,this correct way to set up deep groove single row ball bearings instead of using loctite 620 .. PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| dazler Newbie Joined: 21/10/2007 Location: AustraliaPosts: 37 |
@ Cameron sorry no photo. this is what i mean by my rewired 80. a F@p has 42 poles, and can be used for 48v bank. so i thought it could have 2 lots 21 poles be good for a 24v system (2x 7 poles each phase)(3phase total)2s7p. my site is low to mid wind area, i set it up few amps most of the time, not a high winds 7s2p machine. question to all, if i set up a dual f@p all my 80 2s7p would it max out 4amps or 8? cheers daz |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Dazler, your original post included this observation "Hi guys, i am maxing out at 4 amps into a 24v battery bank, but i can clearly hear that its spinning faster and faster past this point?" Gordon has pointed out that this is a function of armature reactance. This is the case. Your last question indicates that you may need more information. This reactance is a function of the ampere turns in the system. ie amps and turns of copper wire. When your rpm got to the point of about 4A for the number of turns of copper in your alternator, the back MMF (magnetic force if you will) generated by the 4A travelling through your turns of copper, became of such force and opposite sign to the ferrites, as to interfere strongly with your ferrite magnet force. The end result of this is that no matter how much faster you turn it after this point, the ferrite can't seem to manage to get any more flux past this opposing field into the coils to develop more power... it is a stalemate. Thats why you could hear it run up past your max current, but with nothing to show for it. As it is an ampere turns problem, it is not really a power problem. If you use a higher batt voltage eg 100v, the current will still be limited by the 4A you observed, but the voltage can rise.... yes, you now get 400w out if you spin it fast enough..... 200v 800w etc. (because the turns and current are still the same) It is an ampere turns problem, so if you use two units, and each apparently limiting at 4A.... then combined it will be 4A+4A=8A@ your 24(28)v... I think that may help explain the "quirk". If you can add more magnet (neo etc) and get rid of some turns to keep the cut in the same, then this problem can be pushed back a bit further.... because of stronger magnetic field from neo's (so need more current to set up a stronger opposing field) and less turns to do it.... win win. If your cut in is really too low anyway, you can rewire for lower turns per phase (paralleling coils or taking some turns off the coils), or running delta or independent rectification if you are currently star etc etc... all to get lower ampere turns. ............oztules Village idiot...or... just another hack out of his depth |
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| dazler Newbie Joined: 21/10/2007 Location: AustraliaPosts: 37 |
Thanks oztules and the you time to write the post. I did miss what Gordon was trying to point out. This explain whats happening and the way i can improve my system. cheers darren |
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