Abstract

Subject of the present work is the thermal analysis of small axial flux coreless permanent magnet generators for locally manufactured small wind turbines.

An introduction is made on the principles of appropriate technology and the applications of small wind turbines. Furthermore, a comparison is conducted between axial and radial flux generators and their differences are presented. Subsequently, a bibliographic research is conducted on the types and topologies of axial flux generators.

Additionally, the theory of thermal phenomena is analyzed, as well as the mechanisms of heat transfer, alongside the equations which describe them. The thermal limitations of electrical machines and their cooling methods are also examined.

The lumped parameter thermal model is presented and an analytical solution of its equations is conducted for two generators of nominal power 600 W and 5 kW. Based on specific coefficients of the previous model, the thermal behavior of these generators is simulated three-dimensionally via the finite element method under specific operating conditions.

In addition, the same operating conditions are examined in the laboratory and the experimental results are compared with the simulation. The deviations between the various results are calculated and possible causes are studied. Moreover, data is collected from the 600 W generator which has been operating on the NTUA small wind turbine test site and a thermal analysis under normal operating conditions is conducted.

Finally, conclusions are drawn and proposals for improvements and further work are presented.

Keywords: appropriate technology, low cost, small wind turbines, axial flux generators, permanent magnets, thermal analysis, heat transfer, thermal losses, lumped parameter thermal model, finite element method, three-dimensional analysis, outdoor testing

Author: Vasilis Karatasos

Responsible PhD: Kostas Latoufis / latoufis@power.ece.ntua.gr

Supervising Professor: Nikos Hatziargyriou / nh@power.ece.ntua.gr

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