This article discusses the possibility of applying a cylindrical coordinate system when examining the magnetic field of a synchronous machine.

The article presents some results of studying the most optimal parameters of the displacer and the piston of a low-temperature engine with external heat supply to increase its efficiency when converting low-grade heat. The developed design of the engine does not have a displacer rod, which provides better sealing and reduces mechanical friction losses. Synchronization of the piston and the displacer movement is ensured by the permanent magnets interaction. The analysis of the results of computer simulation of the PV diagram with an increased diameter of the displacer in relation to the piston diameter plays a positive role in increasing the efficiency and power of the engine. Increasing the diameter of the displacer also leads to increasing the area of the PV diagram and its approach to the ideal thermal Stirling cycle. The simulation results show that increasing the diameter of the displacer above 17/1 does not lead to increasing the area of the PV diagram, and with a larger ratio, on the contrary, it reduces the parameters of the engine efficiency. Further increasing the diameter of the displacer is not advisable in terms of technical and economic ratios. The proposed engine with external heat supply is capable of converting heat from geothermal or industrial wastewater, as well as heated water using a solar collector.

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Abstract. The article considers the valve converter with a natural current characteristic, which is called the current of parametric, for which the primary is not the source of the electric force but a parametric source of current, to the output of which connected to the counter-parallel thyristor sets assembled on the bridge scheme. The control of thyristors in the current converter is carried out taking into account the characteristic features of the parametric source, to avoid overvoltage on its reactive elements, analyzed algorithmic and modulating functions of the system borne temporary diagrams.