The article discusses the advantages of using liquid hydrogen to cool superconducting electric machines for an all-electric aircraft. Calculation schemes and basic parameters of superconducting electric machines with liquid hydrogen cooling are presented. It is shown that liquid hydrogen is practically a non-alternative type of fuel for future electric aircraft because of its high energy intensity and environmental cleanliness.

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HTS direct drive generators with high specific output mass power and specific output volume power (at the boiling point of liquid nitrogen 77 K) are needed for aviation. Elimination of the reduction unit will reduce the weight of the entire generation system. However, this puts high demands on the strength of the high-speed rotor. Other important requirements are: brushless; the possibility of adjusting the output voltage (by changing the excitation current) depending on the magnitude and type of the connected load; autonomy (no external power supply of excitation current). To satisfy all the above requirements, a fundamentally new technical solution for an electric machine was developed. The generator is a two-package hybrid of the Induction machine with combined excitation. HTS-2G windings (2x3-phases of HTS-2G armature windings and axial excitation coil) are in stationary cryostats on the stator. The rotor has alternating poles of high coercive permanent magnets and ferromagnetic poles. To ensure the alternating magnetic field of the poles of the rotor and to avoid demagnetization of permanent magnets by a counter-directed field of the axial excitation HTS coils, the rotor packages are rotated by one pole. In this case, the demagnetizing part of the axial flux is intercepted by the ferromagnetic pole of the neighboring packet.

This paper describes a universal method proposed by the author for the evaluative analytical calculation of the main parameters of synchronous electrical machines, including superconducting ones. Traditional methods for analytical calculation of parameters to build a phasor diagram of electrical machines require a calculation of all dimensions of the active zone, tooth-slot zone and frontal parts of armature windings. All sizes and local states of magnetic circuit saturation are necessary for the calculation of magnetic conductivities. Traditional analytical methods use, among other things, empirical formulas and non-physical coefficients and allow one to calculate only standard machines with classic tooth-slot zones and armature winding types. As a result of drawing a phasor diagram using traditional methods, the angle between the electromotive force and voltage is calculated, which is the machine’s internal parameter and has no major significance for users. The application of modern computer programs for simulation requires a preliminary analytical calculation in order to obtain all dimensions of the three-dimensional model. FEM simulation programs are expensive, require expensive high-performance computers and highly paid skilled personnel. Fast analytical techniques are also required to assess the correctness of the obtained automatic computer simulation results. The proposed analytical method makes it possible to quickly obtain all the main parameters of a newly designed machine (including superconducting ones and those of non-traditional design) without a detailed calculation of the dimensions of the tooth-slot zone and armature end-windings. The characteristic values of load angles are set according to the results of simple calculations, and the desired values, obtained via plotting, represent the inductive resistances of armature winding and inductive voltage drop across it. Results of practical significance, calculated from the voltage diagram, are as follows: the inductor’s magnetomotive force necessary to maintain the nominal load voltage value, regardless of the magnitude (including double overload) and type of the connected load, or the main dimensions of the active zone.