F&P Stator Rewiring

From factory the Fisher & Paykel stator is wired into one large star winding, producing 3 phase AC when used as a generator*. If we were to use this on our windmill the output voltage would range from 0 to 300 volts unloaded, and up to 2-3 amps maximum loaded, not a very usable range for charging batteries.

The standard stators have either a string of 14 or 12 poles for each phase. 3 phases, means 42 or 36 poles total, depending on what model stator you have. We are going to rewire the stator into shorter strings to reduce the voltage, and then connect these strings in parallel to increase the current.

* Technically its an ALTERNATOR, but the term GENERATOR is more commonly used.

There are 2 F&P Smartdrive combinations commonly used for our windmill alternators, the old 42 pole stator, and the new 36 pole stator.

First up, the old 42 pole conversion. The 42 pole stators are still the most common and easiest to source. Click on the image to see the full size diagram.

At right is a diagram of the stator factory winding. I've labeled the phases X Y & Z. Remember you can click on these diagrams to see full size. This a 1 group of 14 poles, so each phase consists of 14 poles.
This is how we rewire the stator as 7 groups of 2 poles star configuration, and is the easiest and most common way to modify the stator.
And this is how we can wire the stator to use for either star or delta configurations. Anyone who read the Silicon Chip articles I wrote will be familiar with this layout. The star/delta option gives you the ability to connect the stator as a star or delta. Delta will produce more power at high revs, but star will start making power at lower rev's and is the preferred option.
The standard stator. First remove traces of corrosion and file off any rust on the laminations
Cut the winding at every 6 poles. This will give you a total of 7 groups of windings, each with 6 poles, 2 poles per phase. Remember you can click on these photos for a closer look.
With sandpaper, clean the enamel off all leads for approx 15mm from ends.
If you are making a 3 wire star stator, twist and solder the star mid point connections.
Strip lengths of wire as shown. Use wire capable of at least 15amps.
Solder three ( or six if you are going for the 6 wire star/delta option ) lengths of heavy electrical cable ( 4-5mm dia copper ) to the original connection terminal terminals, then strip back 5mm at each connection point. Cut the cables at the last connection point. This will form our power "bus". Wrap each star end wire around the bus wires as shown, and solder. You will need a good soldering iron for this.
Once all star windings have been soldered, cable tie the bus wires to secure the assembly.
The finished stator. Give the stator a good coating of varnish ( or similar ) to protect from the weather.
If you decide to wire as a 6 wire delta/star configuration, you stator should look something like this.
If you use a 6 wire star/delta configuration, the diagram at right will show you how to connect the output leads together.

Next we'll look at the new 36 pole stator. I havn't done any testing with this model to date, but reports from others indicate slightly less power than the old 42 pole stators. However, the new 36 pole stators don't have any of the cogging problems that have plagued the 42 pole stators for years. The 32 pole also give us a larger range of re-wire options ( 36 divides down better than 42!)

The suggested rewire diagrams are a guide only, there are no "use this re-wire with this turbine to get this voltage" rules at this stage.

This is the standard factory wiring. This would work best for a slow running windmill, like a savonius type.
Rewired as 6 poles in series. Again suitable for low speed turbine or high battery voltage ( 48 volts or above ).
Rewired as 4 poles in series. Suitable for low speed turbine on 12 volt system or high speed turbine on 48 volt system. General all rounder.
Rewired as 3 poles in series. 12 or 24 volt systems. Another general all rounder.
2 poles in series. 12 volts, high speed turbine.

There are also a couple of other rewire options you may like to consider.

The 7 phase conversion. This uses a 42 pole stator with the magnet hub from a 36 pole stator, a real mismatch in components. By itself, it doesn't work, no output, but if you rewire the stator as a 7 phase alternator, you get very good power output and no startup cogging problems.

Details here.

Staggered windings. Not yet documented properly, except for these threads in the forums...

http://www.thebackshed.com/windmill/forum1/forum_posts.asp?TID=749&PN=0&TPN=2

http://www.thebackshed.com/Windmill/FORUM1/forum_posts.asp?TID=751&KW=staggered

The staggered stator rewire means we make the strings of different lengths. Example, 42 pole stator, instead of 7 groups of 2 poles in series, we might use one string of 5 poles, one of 3 poles and 3 of 2 poles. This gives a better windmill cut in, makes better use of light winds without stalling the turbine.