Abstract
Aimed at the problem that the existing calculation method of eddy current losses in stator windings of large hydro-generators cannot consider the transposed structure and circulating current, the equivalent circuit model considering the actual transposed structure and circulating current is established, and the analytical calculation method for eddy current losses of stator winding is proposed in this paper, which is suitable for different transposed structures. Then, eddy current losses of stator transposed winding in an 180MW hydro-generator is analyzed by the proposed method and validated by the finite element method. Finally, the influence of the transposed structure on eddy current losses of stator windings is analyzed quantitatively and compared with the existing calculation method. The results show that the value and distribution trend of eddy current losses in strands change a lot when considering the influence of circulating current and the actual transposed structure, and the influence is different for different transposed structures, which must be considered.
Highlights
The accurate calculation of additional losses in stator windings of the large hydro-generator plays an important role in the design of stator windings and is the prerequisite for the subsequent temperature calculation [1], [2]
Additional losses in stator windings of the large hydro-generator mainly consist of circulating current losses generated by circulating current between strands in one stator bar and eddy current losses generated by eddy current in one strand of the stator bar, which are all caused by the leakage magnetic field
In order to reduce circulating current losses, the transposed structure is adopted by parallel strands in slot portion [3], and every transposed strand changes its position in stator slot along the axial direction of generator, leading to the leakage magnetic flux linked by one transposed strand is different along the axial direction, which will affect the
Summary
The accurate calculation of additional losses in stator windings of the large hydro-generator plays an important role in the design of stator windings and is the prerequisite for the subsequent temperature calculation [1], [2]. In the existing method for eddy current losses in stator windings of large hydro-generators, it is assumed that circulating currents between stator strands in a stator bar are ignored and the distribution of leakage magnetic field along the axial direction is the same in the stator slot, eddy current losses can be obtained by solving the leakage magnetic field in a two-dimensional stator slot section [25] and the transposed structure and circulating current are not considered. The slot leakage magnetic flux is represented by the slot leakage reactance, the equivalent circuit model of every transposed strand in every transposed pitch for calculating the eddy current loss can be established, which is shown as Fig..
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