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Simply the Motor part

PostPosted: Mon Oct 11, 2010 5:34 pm
by chadley
Hi There,
Newbie wind generator builder, (angry with internet scams...) looking for real answers to energy savings in SA after R1000+, 4 months and 12GB of internet searches and useless incomplete reading on the web.

I am very eager to get cracking on a project of my own, since the only plans people can get their hands on in the global energy crisis! costs $100 (power4home), which I paid and never got my plans or, the company doesn't respond to quueries, they don't answer thier phone etc... I have decided to take a different route. Seems that there is a lot of embezzling going on online now days and to actually get a starting point is more frustrating than I can bear. So I have decided to learn by blowing things up. ( well hopefully not to much). I also thought I should join a group, since this one hit my search the most, and I like Windgat comments. I picked here.

Being resident in SA, I need to figure out if I can run a Wind turbine where I stay PTA northorn face of the magaliesberg, it seems like we have a fair amount of medium to slow wind.

First Question if I may:
Now for building a generator, how would using an induction motor fair as a wind turbine? Has anybody tried this, it produces 3 phase power and 220v approx 740w per 1 HP. ( that's if I understand things correctly)
I am not afraid to build my own stators and coils, but for the first stage of my project I would really like to see some volts...

Second question:
Does anyone here have a set of plans for PVC blades? or is there a formula to work out how the blades and the motors should be balanced. I would realy appreciate some guidance as I have only a general idea of where to start.

Re: Simply the Motor part

PostPosted: Tue Oct 12, 2010 10:06 pm
by windgat
Welcome to the quest!

1. What RPM is required to generate the voltage you require? That is the crucial question - start there. You may find a very high RPM is needed - see posts elsewhere on this site re alternators.

2. I don't. There is a blade calculator on the main page however that can be used to calculate the optimal blade config for some aerofoil shapes. If you come somewhere close to optimal it will still perform surprisingly well. PVC can deteriorate in sunlight and become brittle. Other plastics may last longer.

If you do make some PVC blades post some pics here!

Re: Simply the Motor part

PostPosted: Wed Oct 20, 2010 11:19 am
by chadley
Advise to the genral group.
Using an induction motor is a bad idea. (It can wrok so don't get me wrong)
Induction motors require "exiting" this to put it simply means you need to run a constant charge into the coils to generate a magnetic field. The coils create a magnetic field in the rotor.
If you induction motor is rated @ 1750 RPMS ( very hard to achieve in wind) you would need to get the motor turning @ aproximately 6% faster. So you would need to have your turbine on a pulley assembly making it bigger and bulkier, and the will be a lot friction making it less efficient.

The alternator... This one caught me by surprise. The average cheapy you can pick up for around R250, But that will only be around a 50AMP @ 14 volts which is perfect for charging batteries if you can get the RPMS. The alterantor also has a voltage regulator which simplifies your wiring.
The big problem is again the RPMs. The pulley for the windturbine(blade Side) would need to be about 450mm, and on the alterator about 60mm to produce 2000RPM required on the alternator @ about 267 RPM blade speed. On a 50 AMP you need to achieve just over 2000 RPMS to produce 13.8V and about 8AMPs. The other problem is that the alterator will not just produce charge by turning it. You also have to excite the motor. "Yes" it is also an induction motor. The ideal alternator to use is a modern one. any alternator rated over 90AMP.
Which means it will create current at lower speeds of course. (these are for all the cars that have fancy airconditioners and electric systems that must run when the car idling) The preferable alterator is about 150AMPS. (from the scrap Yard you pay around R1200 for one of these and that price tag is a problem by my idea of scrap.
The 150AMP Alternator taken from one of the newer Audi's was on the Bosh Alternator test bench this week, we managed to get 13.6Volts and 8 AMPs out it at about 600RPM. (This is very slow for an alterator) and when you load the alternator it will slow down. So the problem with alterantors are not just the cost, exciting and RPMs. The wiring is a problem as well. The basic Alterator needs a switch and it needs a Pilot light connected for it to produce power. See the diagram I found on alterator wiring attached. Most importantly it must be connected to the battery at all time or it will stop producing a charge.

Now if you have a machining shop or a place where you can have some machining done. You could rebuild the rotors on both the Induction motor and the alternator and fit permanent magnets. This will then make a nice neat generator for you windwill. I have neither so I am at a dead end.

I will now investigate the options of using a wheel hub assembly to build a generator for my windturbine.

Re: Simply the Motor part

PostPosted: Sat Oct 23, 2010 5:27 pm
by windgat
Thanks for that detailed info!