Master Thesis on 2F Generator

[An Stina]

Hey everyone,

I'm part of a German group that helps people build their own "Hugh Piggott wind turbine". As I'm a student too I figured out to write my master thesis about the generator of the 2F turbine as this is the turbine type we build mostly and we have had some troubles with both the construction and the efficiency. The main idea would be to improve the stator by implementing metal cores made out of lamination or iron powder. Has anyone experience with this?
Also I am looking for problems others have faced during the construction process of the generator. I would like to know
1. What kind of problems have you faced?
2. Have you any suggenstion on how to fix this problem? Have you maybe even tried some alternative production tecnology?

Regards,
Anna

[Hugh Piggott]

hi Anna and everybody,

I am very happy to try to help you with any problems.  After all my main objective has always been to provide simple methods to produce an efficient turbine, so I am very interested to learn about production problems, and about lack of efficiency.

The question of putting a core in each coil comes up from time to time.  The reasons why I do not advise this are as follows, but please do try it out if you want to!

• The magnets will tend to seek the cores so you will tend to produce a "cogging" torque that locks the blades and makes the turbine hard to start.  This cogging can also produce vibration leading to stress and noise.
  
• I live off-grid and I am much more interested in energy in low winds when the battery is low, than in maximising energy capture in high winds.  Using a core in the coils will create extra losses in low winds when there is very little power available, so  it reduces the efficiency when I need it most.
  
• Often a core will increase the leakage reactance of the coil to the point where it cannot deliver more than a certain current.  This can lead to overspeeding of the alternator in strong winds.
  

It may be possible to avoid these problems and to make a better alternator.  But you need to be aware that these are possible downsides of using a core in the coils.

I hope this helps

Hugh

[anst...@gmail.com]

In September we built the 4 m diameter turbine. Everything went fine BUT the steel discs. After the pouring the resin started to show ruptures. We filled them with additional resin but after a while there were new cracks. It look a little bit as if the magnets cause some kind of stress in the resin as all ruptures are located at the edges of the magnets. Has someone ever experienced something similar and could help us with fixing this problem?
Regards,
Anna

[Hugh Piggott]

hi Anna,

I have never seen cracks like this before but I think the cause is a high temperature in the casting when it set.  As the casting cools, this causes high stresses in the resin and the resin will crack.  I am told that this is what happens.  

I am wondering if you added enough powder (talcum powder or ATH powder) to moderate the reaction and prevent it overheating?  One of the main reasons I add this powder is to avoid exothermal runaway in the casting and avoid having cracks in my castings.  so my castings never do have cracks in them.

Let me know:

What kind of resin was this?

How much catalyst per how much resin?

How much powder and what type?

Did you use any fibreglass to reinforce it?

cheers

Hugh