We've been working on our generator for our hydro scheme. Heres a blow by blow account:
Cast magnet disk with 8 neodymium magnets. Held with super glue to brake disk and then potted with polyester resin, with a layer of fibre glass mat on top to reduce risk of damage. We tested the aptitude of the glass mat by letting lots of metal tools hit it really hard...
Heres a photo: http://photos-d.ak.fbcdn.net/hphotos-ak-snc1/hs158.snc1/5896_637878390041_61015191_38940443_867659_n
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Fixed magnet disk to hub. We got a garage to help with the removal of the hub nut- next time we will loosen it before taking the assembly off the car. The hub was greased and reassembled such that it span freely.
Made test rig to determine turns required per coil. Bike computer used to measure RPM, span rig with power drill.
Heres a photo: http://photos-g.ak.fbcdn.net/hphotos-ak-snc1/hs158.snc1/5896_637878509801_61015191_38940454_848323_n
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Six coils were then produced with 65 turns, two in hand 1.4mm wire. This was done with reference to HP and the results of the tests. Designed such that we could run at 12V (400RPM ish) or 24V (800 RPM ish) so that the stator could still be useful if not used in this project.
The coils were then cast into a polyester stator using a wooden mould. All starts and ends of coils were routed out of stator so that they could be connected in any combination.
The stator was then mounted on the frame, and the second rotor disk (no magnets) was lowered into place to give an air gap of around 18mm (stator = 12mm thick, 3mm clearance either side). The machine was spun with a power drill- the first rough test results are below- it actally worked!! (though maybe not perfectly yet). Halogen bulbs (12V 50W) were used to load the generator, connected through a 3 phase bridge rectifier. The generator was connected in star with two coils in series per phase.
Generator test- no load
speed (rpm) Voltage (V)
- 12.2
- 14.2
- 20
- 21
- 24
- 28.3
- bulb (current = 4A)
- 12
- bulbs (50W each) in parallel
- 6.5 15 Amps approx.
Heres a link to a photo:
http://photos-c.ak.fbcdn.net/hphotos-ak-snc1/hs138.snc1/5896_637878644531_61015191_38940466_1212478_n.jpg
Things we have discovered:
-When assembling the generator we found that a drill press/pillar drill is essential to ensure all holes are drilled perpendicular.
-The coils could be wound tighter to fit within the arc of the magnets better.
-When cleaning up the stator after moulding, careful not to sand through any wires.
-A bit of wood is useful to protect the rotor from wayward spanners.
-Being a perfectionist in this situation would be good, as would the ability to measure something accurately.
-Having a big workshop and people to make stuff with is super fun.
So....anyone got a good source of decent pelton cups or complete pelton wheels?
Hertha, Matt, Andy and co.
p.s. hope the photos work, if not we'll upload them at some point.
