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1.4 Metre Diameter 3-Blade Wind Turbine Construction
1.4 Metre Diameter 3-Blade Wind Turbine Construction
10 kW, 15 phase Axial Flux Pancake Generator
for 2-Blade Wind Turbine
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Abstract
A 10 kW permanent magnet electric generator has been built and tested for use with a high tsr 5 m blade diameter wind turbine. The system was configured for 15 phase, 15 coils and 16 poles. Each coil is individually rectified to dc, reducing cogging and allowing better control over the output voltage. Total cost of the generator was AU$873 and was constructed with typical home-workshop tools.
Keywords: Wind power, Permanent Magnet Generator, 10 kw wind turbine
Figure
 
Page
1
Rear half of the generator rotor
2
2
Front half of generator rotor
2
3
Generator stator
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4
Front half of generator rotor with magnets attached
3
5
Assembled generator
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6
Testing the assembled generator
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7
Measured RMS Voltage under no load, internal resistance is 2.5 Ohms
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8
Measured voltage into matched load (2.5 Ohm)
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9
Measured RMS power generated for all 15 coils into a matched load
7
LIST OF FIGURES
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Free Wind turbine Plans for 500W
blades included with each purchase.
Free sample chord sections can be generated for
0.70 m to 0.80 m blades (550 Watts - 710 Watts).
Design custom blades for your generator and calculate power output at each wind speed.
2. Generator Assembly
1. Construction of the Permanent Magnet Generator
Figure 1. Rear half of the generator rotor
The rear plate (rotor) is mounted on a trailer axial bearing, it holds the first set of 16 neodymium magnets.
Figure 2. Front half of generator rotor
The front plate holds the second set of 16 neodymium magnets, this plate is bolted to the rear half of the generator rotor completing the magnetic circuit.
15 Independent coils have been fixed into the stator using 24 hour epoxy resin. The coils have a thickness of 12 mm, they measure 2.5 Ohms each and are wound using 0.6 mm diameter wire. This stator will be remade out of fibreglass, and the holes in the centre of the coils will be reduced to increase the power output. Epoxy and aluminium should be avoided in the generator due the fact that epoxy softens in as little as 60oC and aluminium has no fatigue limit, any infinitesimally small stresses will eventually cause failure.
Figure 4. Front half of generator rotor with magnets attached
Figure 5. Assembled generator
The generator was assembled with the stator coils sandwiched between the two sets of magnets, 2mm of clearance was given between coils and magnets. Care was taken assembling as the magnetic force acting on the 32 magnets can be up to 640Kg!
The generator spins feely until current flows, this is due to no iron being in the stator and the absence of cogging greatly helps starting in very low wind.
Figure 3. Generator stator
The neodymium magnets used are grade N38, (2 inch x 1 inch x 0.5 inch) and are magnetised through thickness.
16 magnets are fitted into the slots of both the front and rear plates. The magnets are arranged with alternating poles
around the circumference of the plate. 32 holes have been drilled into both plates to help cooling of the coils.
3. Total cost of the Permanent Magnet Generator
System cost (AUD)
Total cost $873
Magnets $500
2000m 0.6mm magnet wire $88
2 Trailer axles $60
Steel $50
Primer and enamel paint $70
Welding rods $20
Bolts and nuts $20
Connector strips $25
Metal cutting discs $40
4. Testing the Permanent Magnet Generator
Figure 6. Testing the assembled generator

Voltage and frequency was measured on a oscilloscope, generator speed, open circuit voltage, and voltage under load (2.5 Ohms) was measured. Speeds above 500RPM generated considerable heat and requires cooling.



5. Measured results of the Permanent Magnet Generator
Figure 7.  Measured RMS Voltage under no load, internal resistance is 2.5 Ohms
Figure 8.  Measured voltage into matched load (2.5 Ohm)
Figure 9. Measured RMS power generated for all 15 coils into a matched load
P = 15 x (V2 / R)
6. Equipment used
Arc welder
Angle grinder
Drill
Hacksaw
Oscilloscope
Auto-transformer
7. Conclusion
A generator capable of generating up to 10kW built using cheap readily obtainable parts for a total cost of $873, this compares favourably as an inexpensive alternative to the commercial generators.
The generator was tested by attaching the drill to the generator. The speed of the drill and generator was controlled by an auto-transformer. Only one of the coils was put under load. The power produced by the coil was multiplied by 15 to get the total power of the generator.
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