In the article, the problem of improving the technique for the calculation of the geometry of a brushless direct current motor with U-shaped stator for lightweight means of transport and obtaining, at the project phase, relevant relations for its major quantitive characteristics is posed. The peculiarities of analysis of such motors, which are the fundamental part of the mathematical model for design calculation of the motor geometry, are discussed in the article. As a result, the technique for preliminary determination of the stator inner bore diameter of such a motor with permanent magnets on the rotor is proposed.

The relation for calculating optimal geometry of the tooth-slot zone, which is based on the determining the optimal dimensions of the stator lamination sheet and depends on the chosen criteria, is obtained.

The equation (13) enables the calculation of the dimensions of the stator lamination sheet at different limitations, for example, if it is necessary to ensure a given relative copper resistance. Applying the equation (13), it is possible to determine values of relative flux densities and in the teeth and in the frame yoke according to given constructional factors and check the observance of the condition .

- V.Tkachuk,
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*Proc**. VIIth International Conference «Perspective Technologies and Methods in MEMS Design» (MEMSTECH)*, p.120-123, Lviv-Polyana, Ukraine, 2011.