Testing Small Wind Turbine Generators - Renewable and ...

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1/2”. The next has an inside diameter of 1/2” and an outside diameter of 1”. Finally, asprocket with an inside diameter of 1” and the required 21 teeth is attached to this effective1” shaft. Unlike the flat sprockets mounted on the electrical machines, this sprocket has athick hub with set screws to secure it to the shaft. Figure 2.7 shows the sprocket mountedto the optical encoder.Figure 2.6. Sprocket mounted on theshaft of a CE&P generator.Figure 2.7. Sprocket mounted on theshaft of the optical encoder.Because a chain failure during testing could be very dangerous, a roller chain is selectedthat can handle much higher loads than are expected. The dynamometer is designed totest the CE&P generator up to its rated specifications: 1 kW at 300 rpm and 48 voltsDC. To produce this rated power at rated speed, a torque of about 32 Nm is expected.Similarly, 1 kW of power output at 48 volts requires about 21 amps. A design limit of 30amps is selected based on the availability of power transistors, as is discussed in the powerelectronics section. Thus when maximum amperage is supplied to the motor, it is expectedto produce no more than 46 Nm of torque. A 21-tooth sprocket for ANSI-40 roller chainhas a minimum diameter of about 3.5”. The maximum expected tension in the chain isabout 1040 N, or 234 lbs. Steel ANSI-40 roller chain has a rated working load of 810 lbs,or about three and a half times the expected working load. It has a rated breaking pointof 4,300 lbs, or about 18 times the expected working load. Based on this analysis, steelANSI-40 roller chain is considered a very safe choice for this application.13
2.3.3 AssemblyUnlike a belt drive, the chain drive does not require any appreciable tensioning. Thegenerator is simply pulled away from the motor until the chain connecting the two is taut.The encoder sprocket is located between the two electrical machines.To keep it firmlyengaged on the roller chain, it is not collinear with their shafts–rather, it is pushed outto the side, so that it deflects one side of the chain and does not contact the other. Thisarrangement is illustrated in Figure 2.8. Note that when the system operates at high torque,the motor pulls very strongly on the generator, developing great tension in one side of theroller chain. It is essential that the encoder not engage this taut side of the chain, but ratherthe opposite slack side. If it does engage (and thus deflect) the taut side, the encoder shaftwill be subject to extreme bending forces as that length of chain experiences more tensionand tends to straighten out. (This was discovered the hard way, during testing.) On theother hand, if it engages the slack side of the chain, the encoder sprocket will remain firmlyengaged–but not subject to these dangerous bending forces.Figure 2.8. Encoder sprocket positioning in relation to drivetrain motion and torques.14
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Page 5: “And now,” cried Max, “let th
Page 8 and 9: 2.5 Control System . . . . . . . .
Page 11 and 12: List of Figures1.1 California Energ
Page 13 and 14: List of Tables2.1 Phase names and a
Page 16 and 17: Chapter 1IntroductionHorizontal boo
Page 18 and 19: Figure 1.1. California Energy and P
Page 20 and 21: Chapter 2System DesignI had investe
Page 22 and 23: instantaneous shaft position, a dig
Page 24 and 25: consist of only one deep channel, s
Page 26 and 27: Figure 2.4. One of two roller platf
Page 30 and 31: Motor ConnectionsPhase Name DC Posi
Page 32 and 33: Figure 2.10. Active motor phases fo
Page 34 and 35: meet these requirements are ON Semi
Page 36 and 37: and to ground. This current flow al
Page 38 and 39: Figure 2.17. Assembled control circ
Page 40 and 41: indefinitely to continuously keep t
Page 42 and 43: difference is divided by the one se
Page 44 and 45: is independent from the main DC pow
Page 46 and 47: 2.6.2 Electrical SystemTo load the
Page 48 and 49: Figure 2.23. Complete dump load, in
Page 50 and 51: Chapter 3TestingThe perception of e
Page 52 and 53: 1. Begin with no dump load resistor
Page 54 and 55: The dynamometer frame was slightly
Page 56: to address this problem.While a sol
Page 59 and 60: 4.1 OverviewOnce testing has been p
Page 61 and 62: is the same for all phases: R P = 0
Page 63 and 64: Curve Number Basis Equation1 T F =
Page 65 and 66: Figure 4.5. Difference between mode
Page 67 and 68: elated to the DC output voltage by
Page 69 and 70: T T = 1 (√ω 3VLM I M − I 2 )M
Page 71 and 72: The resultant model is then checked
Page 73 and 74: Table 4.3 shows the final generator
Page 75 and 76: Efficiency EquationLastly, the gene
Page 77 and 78: Figure 4.8. Generator line voltage:
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more bits of information: the rated
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Chapter 5Summary and ConclusionsThi
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Dynamometer1. The dynamometer is a
Page 86:
BibliographyLieu, P. D. K., Design
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Figure A.1. Primary transistor spec
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Figure A.3. Quadrature optical enco
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Figure A.5. Digital signal processo
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Figure A.7. Three-phase bridge rect
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Figure A.9. Operational amplifier s
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Figure B.1. Dynamic C code, page 1
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Appendix CRaw Test DataFigure C.1.
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