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Technical Project Presentation

2. General Goal . To establish a strong wind-power program at the UNR in collaboration with local industry. 3. Background . In 2001, Mr. David Calley, President of Southwest Windpower in Flagstaff, Arizona, conceived a novel type of an ac generator for small wind turbines The so-called Commutated-Flux Generator (CFG) was a 24 V, 600 Hz, 600 r/min, 120-pole, single-magnet machine No working prototype was builtThe 4.75" (diameter) by 2" (length) generator was expected to produ15

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Technical Project Presentation

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    1. Technical Project Presentation DEVELOPMENT OF A HIGH-PERFORMANCE GENERATOR FOR WIND TURBINES Andrzej M. Trzynadlowski, PhD, FIEEE University of Nevada, Reno

    2. 2

    3. 3 Background In 2001, Mr. David Calley, President of Southwest Windpower in Flagstaff, Arizona, conceived a novel type of an ac generator for small wind turbines The so-called Commutated-Flux Generator (CFG) was a 24 V, 600 Hz, 600 r/min, 120-pole, single-magnet machine No working prototype was built The 4.75” (diameter) by 2” (length) generator was expected to produce 1.5 to 2 kW of power

    4. 4 CFG Principle

    5. 5 CFG Cross-Section

    6. 6 CFG Cross-Section

    7. 7 Project Objective I Develop the CFG, including structure optimization, construction and investigation of a prototype, and preparation for mass production

    8. 8 Description of Work - Extensive computer simulations using Maxwell 3D software of Ansoft have demonstrated fatal flaws of the design - Flux leakage between the South and North laminates, as well as through open switches, was so excessive that less than 10% of the magnet flux linked the coil - The S and N laminates took so much space that only a small coil could be fitted The S and N laminates must be distanced to increase the reluctance between them, yielding unused space in the machine - The single-phase design suffers from a high cogging torque, while a three-phase version is difficult to build

    9. 9 Simulations

    10. 10 Simulations

    11. 11 CFG - Conclusion All efforts on improving the magnetic circuit of the generator have failed Mr. Calley and one of his engineers spent three 16- hour working days at the UNR trying to save the design, with no success The generator, both in the 30- and 60-pole configurations, was not able to exceed 100 W of power Decision had to be made to stop wasting more time on the CFG (which has strained the relations between UNR and Mr. Calley) -

    12. 12 Project Objective II To save the Project, another solution was proposed by the UNR team The new objective was: Develop a simple and inexpensive three-phase generator with a high pole number Target parameters: 2 kVA, 48 V, 600 r/min, 120 Hz, 24 poles The transverse-flux type machine was named a Switched-Flux Generator (SFG)

    13. 13 SFG Principle

    14. 14 SFG Model (outer rotor)

    15. 15 Simulations

    16. 16 Design

    17. 17 Prototype

    18. 18 Prototype

    19. 19 Preliminary Results Correct value of flux density in the airgap (1.05 T) Too low output voltage Certain degree of voltage asymmetry between phases - Apart from the possibility of incorrect assembly, excessive leakage is the most likely culprit

    20. 20 Output Voltage (rms, line-to-line, no-load)

    21. 21 Next Steps Install search coils to determine flux distribution in the machine Based on the results, redesign the generator If possible, modify the existing prototype, or build another prototype

    22. 22 Search Coils

    23. 23 Future Plans – Collaboration With Local Industry As a part of the Project, with NREL’s permission, experiments with an air-core generator developed by a local company Cobalt Energy were carried out Sierra Pacific, a local utility company, co-funded the generator - Cobalt generator parameters: 10 kW, 185 V, 310 r/min, 32 poles, 82.7 Hz The machine has low power density (23 W/kg), but very high efficiency (over 98%). The 10 kW unit weighs 435 kg For comparison, the SFG prototype weighs 34 kg, which, at 2 kW, corresponds to 59 W/kg

    24. 24 Future Plans – Collaboration With Local Industry

    25. 25 Future Plans – Collaboration With Local Industry A spin-off of Cobalt Energy, Mariah Power, plans to develop a line of free-standing and rooftop wind turbine systems based on the so-called Modified Savonius (MS) rotor The SFG may find an application there A pertinent NSWEP Letter of Interest has been recently submitted to NREL (RAX-6-66014)

    26. 26 Future Plans – Collaboration With Local Industry Freestanding Mariah Power’s MS Rotors in Reno and Henderson, Nevada

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