The calculation technique of the magnetic circuit of superconducting synchronous electric machines for perspective aircraft

This paper is devoted to development of a generator with high-temperature superconducting (HTS) field windings, claw-like poles and permanent magnets on the rotor for on-board network power supply of fully electrified aircraft.
Application of permanent magnets on the rotor together with field windings is necessary for power supply provision in case of cryogenic system failure. The magnetic flux of permanent magnets creates the basic value of electromotive force (EMF), and the superconducting excitation windings are necessary for voltage regulation during operation of the generator.
Magnetomotive force (MMF) of HTS field winding is several times more than MMF of a copper field winding. The saturation of some parts of the generator magnetic circuits is possible. Therefore, decrease of magnetic potential must be taken into consideration not only in the main air gap, but in ferromagnetic elements also.
The method of magnetic circuit theory and iteration technique were used for estimated calculation of the magnetic circuit. The distribution of a magnetic flux density is considered to be homogeneous in each element of a magnetic circuit. This allows to investigate the generator with the method of magnetic circuit theory. On the base of the magnetic flux distribution an equivalent scheme of magnetic circuit was developed.
The equivalent current was calculated by the method of electric circuit theory (method of nodal potentials). The equivalent scheme of a magnetic circuit becomes simpler if values of some fluxes are small in comparison with the main magnetic flux. In this case their values are considered as equal to zero, and calculation of magnetic circuit can be carried out on the simplified equivalent circuit. In order to take into account the magnetic saturation effect the calculation was carried out by s method of iterations when values of magnetic permeability of each elements of a circuit are specified in accordance with a magnetization curve on each step of iteration.