F&P stator rewiring.

The standard F&P Smartdrive stators have either a string of 14 or 12 coils (also called "poles") for each phase. 3 phases, means 42 or 36 coils 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.

There are 2 F&P Smartdrive motors commonly used for our windmill alternators, the old 42 coil model, and the new 36 coil model. Where we refer to the stator as a whole, we generally call it a 42 pole or 36 pole type.

To avoid any confusion, we've come up with a new naming scheme to describe the different re-wiring options. Originally instead of the word "coils" we were using "poles" to describe the number of coils or poles in series. This caused confusion, as P ( poles ) can be mistaken for "Parallel". We ended up with 2 different naming schemes that caused a few people to incorrectly wire up their stators.

So the new naming scheme, or "code", is...

• C is Coils ( same as Poles )
• X is Times

The factory 42 pole stator has 14 poles ( coils ) wired in series. So that would make it a

1X14C
( 1 times 14 coils in series )

If we split the 14 coils into two lots of 7 coils, we would half the output voltage and double the output current. This would be a

2X7C
( thats 2 times 7 coils in series )

Most windmill re-wires are using the 42 pole model, wired in a 3 phase star configuration. However, if its a little different, just add the details to the code.

2X7C Delta would be as above but wired in delta.
36Pole 3X4C would be a 36 pole stator wired with 3 times 4 coils in series.
7Phase 2X3C is a 7 phase conversion with 2 tims 3 coils in series.

Re-Wiring the 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 times 14 coils, making it a 1X14C using our naming scheme.

This is a stator "split into two", so we end up with 2 times 7 coils in series. Best suited to 48 volts or 24 volts in low winds.

Using our naming scheme, this would be a 2X7C

This is how we rewire the stator as 7 groups of 2 poles star configuration, suitable for most 12 and 24 volt applications, depending on how fast your turbine runs and what wire size the stator is. See What F&P is it? to identify which stator you have.

This would be a 7X2C

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.

This is a 7X2C Delta

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.

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.

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.

36Pole 1X12C

Rewired as 6 coils in series. Again suitable for low speed turbine or high battery voltage ( 48 volts or above ).

36Pole 2X6C

Rewired as 4 coils in series. Suitable for low speed turbine on 12 volt system or high speed turbine on 48 volt system. General all rounder.

36Pole 3X4C

Rewired as 3 coils in series. 12 or 24 volt systems. Another general all rounder.

36Pole 4X3C

2 coils in series. 12 volts, high speed turbine.

36Pole 6X2C

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 involves re-wiring the stator into groups with different coil counts. Different coil counts mean different cut in RPM's, and this gives a alternator with a better power curve.

Details here