Free Wind turbine Plans for 500W
blades included with each purchase.
Custom Wind Turbine Blade Plans Available from $4.95
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.
1.4 Metre Diameter 3-Blade Wind Turbine Construction
1.4 Metre Diameter 3-Blade Wind Turbine Construction
1 kW Wind Turbine (12.5 m/s)
2-Blades (Carbon fibre), 1.8 Metre Diameter
& Induction motor to PMA conversion
Download PDF Version of this Document
Abstract
A 1 kW @ 12.5 m/s (2 kW @ 17 m/s) 1.8 metre diameter wind turbine was designed and constructed out of carbon fibre. The generator was built by converting an induction motor into a permanent magnet generator. The wind turbine blades power and efficiency has been measured at different tip-speed-ratios and a maximum efficiency of 30% at a TSR of 11.6 was recorded, verifying the blade calculators accuracy. Total cost of the generator and blades was less than AU$200.
Keywords: Wind power, Permanent Magnet Generator, Induction motor to PMA conversion, 1kw wind turbine, carbon fiber wind turbine blades
Figure
 
Page
1
40 Amp car alternator rotor with magnets attached
2
2
40 Amp car alternator rotor with magnets fibre glassed in place
2
3
40 Amp car alternator stator with shielding
3
4
Completed conversion of the 40 Amp car alternator
3
5
Completed conversion a 1/4 hp induction motor
3
6
Wind turbine airfoil cross-sections
5
7
Turbine airfoil cross-sections bolted to frame
5
8
Positive moulds of wind turbine blades
6
9
Negative moulds of wind turbine blades
6
10
1.8 m blade set
7
11
Turbine testing
7
12
Measured TSR vs efficiency
9
13
Measured Power
10
LIST OF FIGURES
Top Wind Turbine Articles
PDF Articles for Download
Related Topics
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.
The generator has zero cogging, this is due to the angled magnets and the 2mm air gap between the rotor and stator. It is configured for 3 phase, each phase measuring 5.6 ohms. Output voltage is 130 Vrms at 1333 rpm increasing linearly with rpm.
Figure 5. Completed conversion a 1/4 hp induction motor
The same technique was used to convert a larger 1/4 hp induction motor into a 8 pole / 3 phase PMG

Power output was measured to be more than 2000 watts at the designed blade rotational speed. The generator has enough power for the 1.8 m diameter blades.
Power output was measured to be less than 500 watts at the rpm of the designed blades. The generator will not produce enough power for the 1.8m diameter blades, it is more suited to 1.0m diameter blades with a high tip-speed-ratio.
Figure 4. Completed conversion of the 40 Amp car alternator
Sheet metal was placed inside the stator to shield the magnetic field from aluminium. Without the sheet metal lining, significant power was lost in the aluminium.
Figure 3. 40 Amp car alternator stator with shielding
- The magnets were fibre glassed in place with two strips of carbon fibre.
Figure 2. 40 Amp car alternator rotor
with magnets fibre glassed in place
- Six magnets were carefully place on a slight angle to reduce cogging of the generator.
Figure 1. 40 Amp car alternator
rotor with magnets attached
Design of a permanent magnet generator was necessary to test and
characterise the blade set. Conversion of a 40 amp car alternator to a
permanent magnet generator was attempted.
1. Construction of the Permanent Magnet Generator
The alternators rotor was turned down on a lathe to accommodate
neodymium magnets.
2. Calculating generator efficiency
Given: The 3 phases are isolated, and connected as 3 single phase outputs  each output is rectified to DC using a single phase bridge rectifier.
At 666rpm, generator voltage Vs = 65Volts,
Rs = resistance of each phase of the generator (5.6 Ohms)
Voltage across Rs = 65 - 48 = Vs = 17 Volts
V = IR
Current into battery = 17/5.6 = 3 amps per phase
V/R = I
P = VI
Power into battery = 48 x 3 = 144 watts per phase
(432 watts for all 3 phases)
P = V2/R
Power Lost = 172/5.6 = 51.6 per phase
Efficiency of generator = 144/(144+51.6) = 73.6%
3. Design and construction of the wind turbine blades
The wind turbine blades were designed using the warlock engineering blade calculator program, the airfoil chosen was NACA2412, two blades were designed to have a tip-speed-ratio of 10.
Figure 6. Wind turbine airfoil cross-sections
The airfoils cross sections were cut out of 3mm aluminium sheets, the sheets were bolted to a steel frame and aligned.
Figure 7. Wind turbine airfoil cross-sections bolted to frame
The gaps between the airfoil sections were filled with aluminium tape, and the back of the tape was fibre glassed in place. Wax and mould release was applied to it and two positive moulds were made.
Figure 8. Positive moulds of wind turbine blades
The moulds were sanded down using the aluminium impressions as a guide, Wax and mould release was applied to the positive moulds and new negative moulds were made out of fibreglass and carbon fibre
Figure 9. Negative moulds of wind turbine blades
Detailing of the positive mould produced a perfect negative mould. This final negative mould was waxed and mould release was applied to it. 220 g CSM fibreglass with vinyl ester resin was applied to each mould, the two mould halves were clamped together after the resin had gelled, and the blade was removed after cure.
The blades were sanded and carbon fibred, using an additional layer of carbon fibre around the hub section, the blades are extremely light weight.
Figure 10. 1.8 m blade set
4. Testing the wind turbine
Wind turbine was bolted to a trailer and rpm, voltage and tsr was measured by connecting the generator to a very high power multi-tap resistor, The turbine was allowed to speed up to an open circuit voltage of 65 V (666 rpm) before the resistor load was connected.
Figure 11. Turbine testing
Measurement of results from the wind turbine
Note: Method of testing turbine generates turbulent wind affecting efficiency,
Therefore results should be used as a guide only.
Rs is the resistance of the generator windings plus the power cable; 5.75 ohms
Rl is the resistance of the load; 6.6, 10, 15, 21.5 and 25 ohms
Power generated by the blades was calculated by dividing by the efficiency of the generator,
Once the blades have been characterized, a new generator will be designed
Power generated by the blades are calculated by the following:
Voltage across the resistor load was measured Vl,
Vs = Vl x [(Rs + Rl) / Rl ]
Power produced by blades, and lost in generator, power cable and resistor load is given by;
P = V2/R
P = Vs2 / (Rs+Rl)
Rotational speed (rpm)
Power (watts)
Blade efficiency
Tip speed (km/h)
Tip speed ratio
Figure 12: Efficiency vs TSR
 
25 ohm
21.5 ohm
15 ohm
10 ohm
6 ohm
30 km/h
820
766
809
   
40 km/h
1302
1363
851
645
 
50 km/h
1753
1676
1489
1291
1105
60 km/h
 
2365
2098
1744
1607
 
25 ohm
21.5 ohm
15 ohm
10 ohm
6 ohm
30 km/h
208
205
300
   
40 km/h
524
649
332
252
 
50 km/h
950
981
1017
1008
940
60 km/h
 
1953
2019
1873
1990
 
25 ohm
21.5 ohm
15 ohm
10 ohm
6 ohm
30 km/h
0.23
0.23
stalled
   
40 km/h
0.24
0.30
0.15
stalled
 
50 km/h
0.22
0.23
0.24
0.24
stalled
60 km/h
 
0.27
0.27
0.25
0.27
 
25 ohm
21.5 ohm
15 ohm
10 ohm
6 ohm
30 km/h
278
260
275
   
40 km/h
441
463
289
218
 
50 km/h
595
569
506
438
375
60 km/h
 
803
712
592
546
 
25 ohm
21.5 ohm
15 ohm
10 ohm
6 ohm
30 km/h
9.2
8.7
9.2
   
40 km/h
11.0
11.6
7.2
5.5
 
50 km/h
11.9
11.4
10.1
8.8
7.5
60 km/h
 
16.1
14.2
11.8
10.9
Figure 13: Measured Power, Power (Watts) vs Speed (m/s)
6. Total cost of the wind turbine
System cost (AUD)
Induction motor $15
Magnets $80
Moulds $72
Two Blades $14
Total cost $181
Conclusion
Design of highly efficient blades means smaller size blades for same power, Smaller size means higher rpm and higher rpm makes a smaller and cheaper generator.
Home  |  Contact  |  FAQ