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The purpose of this article is to develop a starter-generator (STG) with reduced supply voltage of 27 V for a turbofan engine. The analysis has showed that the existing design schemes of the STG are mainly designed for high voltage, due to the complexity of the implementation of the power converter. As a result of the conducted research, a method for increasing efficiency has been proposed by modifying the phase commutation control method, and a power converter topology that allows all the operating modes of the designed STG has been developed. In addition, in this article, a comparison of two methods of phase commutation, traditional and with a modified angle has been presented and its result shows the difference and the prospects, as well as the effectiveness of the chosen solution. Thermal calculations have confirmed the possibility of providing all the necessary operating modes, in which the temperature of the active elements has not exceeded the permissible values. The resulting technical solution of the STG has a mass of the active part of no more than 6.09 kg, and it allows providing an output power of up to 40 kW in all the operating modes, at frequencies from 1000 rpm to 12367 rpm. [ABSTRACT FROM AUTHOR]

This paper presents a multidisciplinary design algorithm of the ultra-high-speed electrical machine (UHSEM). Presented algorithm enables UHSEM design with a rotational speed of 0.5–1.2 Mrpm, taking into account the mutual influence of thermal, mechanical, and electromagnetic processes. Based on the algorithm, the 138 W UHSEM with a 1.2 Mrpm rotational speed was calculated. Material selection for the active parts of the machine is described. Analysis of the suitable bearings for UHSEM application is presented. Mechanical, electromagnetic, and cooling design aspects are shown with example of the calculated machine. To evaluate the effectiveness of the developed computer models and the calculation method, the experimental model of the 100 W UHSEM was tested in the motor mode at the rotational speed of 500 000 rpm. The test results demonstrated that the multidisciplinary design algorithm has high accuracy and is suitable for UHSEMs. The discrepancy between developed models and experimental results does not exceed 7%. [ABSTRACT FROM AUTHOR]

This paper solves the problem of minimizing losses in the stator magnetic core of high-speed electric machines with the use of amorphous iron. A fundamentally new technology for manufacturing of a stator magnetic core from segments of amorphous steel is developed by the authors. The feature of the new stator design is the possibility to use technological ducts located inside the stator as cooling ducts. This aspect significantly improves the heat dissipation from the active zone of the stator and, accordingly, minimizing temperature. The efficiency of this solution was studied using two power generators of 100 kW and 200 kW and rotational speeds of 60,000 rpm and 45,000 rpm respectively in the software complex Ansys Maxwell. Harmonic compositions of currents and voltages, flux density distributions in active elements of the generator in various operating modes were studied: under load, in a three-phase short-circuit and at idle. Also, the obtained data were compared with analogous models of an electrogenerator made of electrical steel. The results of the study showed the operability and effectiveness of the proposed technology. Based on the results of the research, a prototype of the stator magnetic core made from amorphous iron was created. Losses in the generator were experimentally measured. Also the results of experimental studies of aerodynamic losses are presented. [ABSTRACT FROM AUTHOR]

This paper deals with a transformer-rectifier unit with a magnetic core made of amorphous steel. Transformers with various types of amorphous alloys have been compared. The most optimal amorphous alloy to use in a transformer is determined. The simulation of the electromagnetic and thermal processes occurring in transformers with a magnetic core made of amorphous steel was carried out, the amplitude and shape of the voltage and current were determined and the maximum temperature in nominal operating mode was defined. The dependencies of the specific losses in the studied samples of amorphous steel on the frequency of magnetization reversal, magnetic flux density and temperature were obtained. An experimental layout of a transformer rectifier unit with a magnetic core made of amorphous steel, loaded onto an 18-pulse rectifier with a power of 10.5 kVA and operating at a frequency of 400-800 Hz with a voltage of 115/27 V was designed and manufactured. An experimental study was carried out on the developed layout to verify the obtained data. The experimental studies confirmed the correctness of the chosen design methodology and of the design scheme of the transformer. It is important to note that the thermal loads detected on the transformer during its testing are within the permissible values. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical description of the electromechanical energy converters with permanent magnets. Unlike well-known mathematical models the mathematical description is obtained by the joint solution of Maxwell and Fourier equations. This allows to determine the geometric dimensions of the active part of electromechanical energy converters taking into account thermal and electromagnetic processes on the stage of the design calculations. Finite element method is used for the final calculations of the full geometry of electromechanical energy converters. Computer simulation and experimental study of electric machines with high-coercivity permanent magnets were investigated to evaluate the effectiveness of the obtained results. The results of experimental studies have been compared with mathematical model and its high accuracy was obtained. [ABSTRACT FROM AUTHOR]

The article presents a new topology of the high-speed synchronous electrical machines with permanent magnets with the tooth-coil windings with a stator magnetic core made of amorphous alloys for prospective unmanned aerial vehicles. This is a multidisciplinary design algorithm with optimization elements, which are proposed to design such machines. Based on the proposed algorithm, calculations of several topologies were performed by using computer simulation methods. In addition, the analysis of the rotor dynamics as part of the turbojet engine of the unmanned aerial vehicle and the calculations of the mechanical rotor strength were performed. To minimize the eddy-current losses in permanent magnets, the multicriteria optimization of the slotted zone was carried out by using genetic algorithms. A cooling system was proposed, and thermal calculations were performed. To verify the proposed design algorithm and to evaluate the efficiency of the amorphous alloy, a full-sized 5 kW experimental sample with a rotational speed of 60,000 rpm was created. Results can be used to create new promising UAVs and to design electrical machines for other industrial applications. [ABSTRACT FROM AUTHOR]

The paper presents a study of dynamic thermal processes in ultra-high-speed microgenerators power of 55W with the rotational speed of 800,000 rpm for UAV. A large-scale study of current works devoted to this topic were done where the main shortcomings were identified. A mathematical description of heat exchange processes in microelectromechanical energy converters with a flight time of no more than 10 minutes was developed in a non-stationary formulation. A study of the thermal state of the microgenerator operating in a short-term mode without a special cooling system is conducted. An experimental study of the heating dynamics of its active parts is carried out using the method of physical analogies. On the basis of experimental studies, the FEMM model is verified. Afterwards, combined electromagnetic and thermal calculations of microgenerator are conducted. [ABSTRACT FROM AUTHOR]

The article presents a research of the effect of different types of short circuits (SC) on the performance of the gas turbine and ultra-high-speed microgenerator (MG) in a wide rotational speed range (from 200,000 rpm to 1,000,000 rpm) at a power from 10W to 1 kW. The studies are carried out on a specific two-pole 100W 500,000 rpm microgenerator with permanent magnets with a toroidal winding. The research is carried out by finite element method using Ansys Maxwell software. Numerical study by the finite element method is performed at the rated operation mode and various types of short circuits: single-phase, two-phase, three-phase circuits coil inside MG. By the results of these studies, we estimate a negative impact of different types of faults on the parameters of MG and the mechanical characteristics of the gas turbine. Also various options MG with SC for various types of bearings were considered. Then, using the full-sized 100W sample we carried out experimental studies of the MG operation in nominal operation mode at the 500,000 rpm. That allows to verify the developed computer model and confirm the results of our practice research. The obtained results can be used in the aerospace industry for design the high reliability complexes such as new energy systems for satellite power supply, unmanned aerial vehicles and microturbines. In addition, it can be used to design the ultra-high-voltage electric machines with a high fault tolerance for the compressor plants, air supply systems of hydrogen fuel cells, new medical tools and machine tools. [ABSTRACT FROM AUTHOR]

The paper presents the experimental research of different slotless high-speed electrical machine topologies for integration into the auxiliary power unit gearless. It was shown that the 6-poles and 8-poles with the concentrated windings and the wound stator core are the most effective for aerospace industry. Based on the experimental and computer research of different slotless high-speed electrical machine topologies. It was found that for use in the gearless auxiliary power unit of modern and perspective aircrafts, the use of the 6-poles and 8-poles slotless high-speed electrical machines with concentrated windings and wound stator core is the most effective. This topology allows providing the sufficient rigidity of the slotless high-speed electrical machine stator core, the minimum length of the frontal part and the minimum weight and size parameters of the slotless high-speed electrical machine at the maximum efficiency. In addition, in this case, the slotless high-speed electrical machine windings have a high inductance, which leads to limit the magnitude of short circuit currents. [ABSTRACT FROM AUTHOR]