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Miscellaneous Questions.
By seanchan00, Section Mechanical Posted on Tue Jul 12, 2005 at 04:50:35 PM MST
Assembling my wind generator.

Hi Board members,
I intended to use AWG 14 double strand 35 turns to make 9 coils for my windgen. It is 12" dual rotor with 24 neodymium 1 x 2 x ½ inch magnets and 15 inch stator powered by 8 feet blades. However here in Malaysia I follow SWG and the equivalent size is SWG 16 diameter 1.63 mm. Now I can only buy SWG 16 ½ diameter 1.5 mm a wee bit bigger than AWG 15 diameter 1.45.
Questions.

    Using SWG 16 ½ double strand, do I need to increase turns to say 40 instead of 35 to match the magnets and blades?
    For my rectifiers, DC fuses and shunt regulator how many amperes do I buy? Are 30 amps enough to handle the expected power generated?
    If I connect the fuse between the rectifiers and the battery bank as I saw in the Windstuffnow diagram, won't the windgen freewheel out of control once the fuse break. The reference for this is here. http://www.windstuffnow.com/main/basic_wind_system.htm
    Isn't it better to connect the shunt regulator between the rectifiers and the fuse before the battery bank?
    How many watts can I expect from this windgen?
Thanks for very useful advice I have had from the board.
SeanChan.

Miscellaneous Questions. | 6 comments (6 topical)

Re: Miscellaneous Questions. (3.00 / 0) (#1)
by Flux on Tue Jul 12, 2005 at 12:45:38 PM MST

There is no need to change the number of turns if you can get the thicker wire in, I think you will have plenty of room. If you can't get it in a few turns less will not matter. Nothing is absolute, if you have the wire go for it and get in the 35 turns or as near as you can.

I would use at least 3 35A bridges with the two ac connexions linked and well heat sink them. If you can get 50A bridges use them and play safe.

If you put a fuse on the generator side of your battery, choose one so big that it will never blow from the power generated, but will protect your cables in case of a dead short rectifier. A blown fuse from any operating condition will cause you a lot of trouble. Also choose a type of fuse that will not age such as an HRC, re-wireable things tend to age and finally fail if they are rated close enough to provide useful protection.

Usually the best place for a shunt regulator is directly on the battery, the input fuse should never blow under working conditions, only if the rectifier fails and this will prevent the generator running away so you shouldn't expect the regulator to have to do this job.

You should easily get 600W and it may peak above this for brief periods without damage.

Good luck, seems like a nice project.

Flux

Re: Miscellaneous Questions. (3.00 / 0) (#2)
by seanchan00 on Tue Jul 12, 2005 at 06:05:21 PM MST

Thanks Flux,

I am forced to use slightly thinner wire as SWG 16,(AWG 14 equivalent), 1.63mm D is not available here. I only have SWG 16.5 which is 1.5mm Diameter, so I reasoned using the thinner dual strand, I needed a few extra turns added to the 35 turns for AWG 14 dual strand. That's why I am contemplating 40 turns.

What amp rating would you recommend for the input fuse. Are fuses used in big trailer lorries good enough for this application? They are easily available and relatively cheap.
I am facing a problem sourcing a shunt regulator. Shops here don't have an idea what it is let alone details of the shunt required. Is there any rating as in rectifiers, fuses and transmission cables? At what volt and above should the shunt kick in?

Clarification.
( Usually the best place for a shunt regulator is directly on the battery, the input fuse should never blow under working conditions, only if the rectifier fails and this will prevent the generator running away so you shouldn't expect the regulator to have to do this job. )

Sorry but I can't quite understand the second part of this reply.
Once the input fuse blow the power generated has no load so the generator will free wheel out of control. Siting the input fuse

directly on the battery and shunt regulator,
between the shunt and the battery,
before or after the rectifiers(as recommended)

won't change the circuit equation. We still have a zero load to control the wind generator and it is out of control in strong winds resulting in a toasted stator.

I was hoping that by siting the shunt regulator before the input fuse but after the rectifiers, there will still be a load on the generator if the fuse blow to protect the batteries. The bank of resistors, heaters, power fans etc taking the shunted load are surely more durable, right?

Thanks again,

Sean.

[ Parent ]

Re: Miscellaneous Questions. (3.00 / 0) (#3)
by Flux on Wed Jul 13, 2005 at 01:05:02 AM MST

Sorry Sean, I didn't spot that your wire is smaller, I thought you were referring to 14 SWG.

There is probably no advantage in increasing the number of turns, you will already have a higher resistance so there is not much point in making it even higher with more turns. Your cut in speed should be about right with 35. I don't think the change in wire size will have much effect.

Automotive or fork lift fuses should be ok. I would use at least 80A.

You seem to be working on the assumption that the generator fuse will blow, if it is big enough it never should. If it does blow the generator will run open circuit and become noisy and frantic but it will not damage the stator. there is no current flowing.

If you can guarantee your shunt regulator to work directly off the generator under all wind conditions and survive then your idea is a good one but if it is capable of dumping the mean excess current, it may still not be able to handle the peak current of a gust.

If you use a fuse big enough not to blow during the highest sustained output the generator will never run away. If for some reason you blow a rectifier to dead short, the fuse will still protect your cables and you will have a generator shorted out by a short circuit rectifier and the generator will come to a stop, just as if you had use a brake switch.

Which method is best will depend on the ability of your shunt regulator to survive directly off the generator. Dump resistors are fine, but the electronics in the controller will not like the rise in volts if the resistors can't hold the volts down, even if the mosfets can handle the current.

If you have to build your own dump controller you could operate the control circuit from the battery and take the sense voltage and dump resistors from before the input fuse but I doubt that you have this option with a commercial controller.

Flux

[ Parent ]

Re: Miscellaneous Questions. (3.00 / 0) (#4)
by domwild on Wed Jul 13, 2005 at 03:20:17 AM MST

Re shunt,

Have a look at Home Power magazine, there is a circuit for a dump controller available on the web.

Just search the web, you will find many references.
dom We only ever use the best fencing wire for our repairs!
[ Parent ]

Re: Miscellaneous Questions. (3.00 / 0) (#5)
by domwild on Wed Jul 13, 2005 at 03:23:38 AM MST

Salam,

Forgot to answer your voltage question: As far as I know, once the batteries of a 12V system reach 14.4V, then the shunt should kick in.

If you get a specification sheet with your battery, then have a look at the manufacturer's speci and follow that.
dom We only ever use the best fencing wire for our repairs!
[ Parent ]

Re: Miscellaneous Questions. (3.00 / 0) (#6)
by seanchan00 on Wed Jul 13, 2005 at 04:24:15 AM MST

Yeah Domwild,

I just spent the afternoon doing just that. The circuit for the homebrew shunt regulator seems easy even for non tech ME that spending good money on commercial shunt is sinful. I even understood the circuit for the electric fence energizor and the shunt to convert small analog milliammeter to read 100 or 150 amps seems manageable now. Probably my continuous reading has improved my learning curve. I will be doing it myself. Will get to the electric fence after the windgen.

However, my first physical attempt at winding the coil ended in failure because the wood winder broke at 28th turn. I was also getting confused with the count at the same time trying my best to line the twin wires evenly to build up layer by layer. I find it quite difficult as the two strands separate every now and again. Any practical tips anyone. The practical is tougher than the theory! I am going to make an all iron coil jig before I try again. I was using chip board made by my carpenter friend. By the way how much and what kind of wax do you guys use in coil making? I heard superglue is applied to hold the coil so it can be removed intact and tight.

Sean.

[ Parent ]

Miscellaneous Questions. | 6 comments (6 topical)

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