Which Voltage should I generate

[alibro]

Hi guys

You may have seen some of my earlier questions and I appreciate your help before. I would like your opinions once again. I am building a 10 foot turbine like the older ones on the Otherpower web site using twelve 2" x 1/2" round magnets on each rotor and 9 coils in the stator. I have the genny mostly built but am now about to make the stator.

   I have an APC 48V 3000W UPS but as it draws around 80W no load from the batteries I will be buying an inverter. I can build the stator for 12V or 24V easily (not sure about 48V).

1. Which voltage would you suggest I build it for?
   
2. How big should my battery bank be to match this wind turbine?
   
3. If you think 48V any idea how many turns required (given that 60 to 70 for 24V and 30-35 for 12V) is it just doubled that for 24V ie 120-140. In the Wind Farm turbines the stator is wired in Star instead of Delta as in the older design. http://www.otherpower.com/windfarm1.html
   
   

Would I be better to keep this configuration if going for 48V?

I like the Idea of using 48V as the losses in the cables are smaller and I can use my APC as a backup, however the inverters seem to be more expensive. I am on a tight budget and was hoping to get the inverter for under a couple of hundred UK pounds.

This system is mostly being built for fun but I intend to run some of the house off it (probably a few lights initially and add stuff if everything goes well) with a switch over to grid for periods of low wind. My cable run from base of turbine to shed is around 50 yards although if this too much I guess I could build a wee shed just for batteries and inverter and run 240V back to the house.

Thanks

Alister

I'm going out to do some work dear not to play!

[Nando]

Go for 48 volts and then when built, measure the voltage versus RPM unloaded, as well, as the winding resistance,then do not wire for star or delta, have the six wires out for star and /delta change that can be done easily measuring the RPM and/or the output current, this way at high winds you may obtain around 65 to 70 % efficiency instead of around 50 with the star configuration alone.

The relay, a 3 pole Double throw ( 3PDT) or the semiconductors to do the switching can be up near the generator with the small detector circuit.

Nando

[DanB]

Yes - if you care to go that route do as Nando suggests - otherwise use Star, or... use star but keep 3 leads there so you can change the connection if the future if you like.

With those magnets, if this is to be a 10' machine, I would wind with 125 turns of #16 gage wire.  Those round magnets are a bit on the large side and all of those machines had stall issues.  They were all improved either with larger blades - or...  a really wide airgap.  If you're planning for 10' though, I'd wind a touch differently.  Or build it like we did and put a slightly larger (11') blade set on there and make sure it furls early.

[alibro]

I bought timber which is a bit longer than 5 foot so I think I will make the blades 11 foot. Does that mean stick with 125 turns or go for a few more.

Can you say what voltage I should expect from each winding at cut-in and what rpm that should be for an 11 foot blade?

I will make a test winding to measure the voltage (with a standard £40 multimeter, I'm not sure if it reads RMS or not).

Any ideas on the battery bank size?