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The paper describes a variable frequency drive which consists of two elements: an electric drive (synchronous or asynchronous electric drives, that is, drives powered by alternating current are used in capacity of it), and a frequency converter able to control the amplitude and frequency of the voltage supplied to the drive. It becomes possible to control the speed of rotation of the electric motor and the torque on its shaft. The most optimal energy efficiency when using compressor units is achieved under the operating mode when its average daily load factor makes at least 85%. Under the mentioned operating mode fluctuations during the compressed air consumption will be minimal, and the most stable operation of the compressor at its rated nominal power is ensured. In practice, no more than 15% of all the industrial compressors are operated in such operating mode. For 85% of the compressor units the question of improving energy efficiency by regulating its capacity remains open. The method of capacity regulation by using a frequency converter is currently the most optimal and perfect, because adjusting the parameters of the electric drive in this way, the most accurate regulation of the compressed air pressure is provided, which allows reducing the energy consumption in the compressed air injection process, as well as extending the service life of the equipment used. There has been considered a device with frequency control of a compressor unit, debugging of which was carried out on the basis of a mathematical model, which allows choosing the most optimal parameters for frequency control of an electric drive of a compressor unit in order to increase energy efficiency. The analysis of all the advantages and disadvantages of frequency regulation is being carried out, as well as a comparative analysis for selecting the optimal frequency converter in terms of the import substitution

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An analytical review of the main methods for improving the working process of marine diesel engines, with a method for their systematization and grouping is provided in the paper. The issue of modern methods and ways of improving the criteria for environmental friendliness, economy and energy efficiency of a diesel engine as the main ship power plant, taking into account the requirements of the MARPOL 73/78 convention, as well as compliance with the Register rules, has been studied. Based on the analysis performed, a block diagram of methods for improving the working process of a marine diesel engine is presented. The proposed block diagram makes it possible for the user to easily select the method of interest for modernizing the operation of the ship power plant, with its further detailed study. The object of scientific research is methods of improving the working process of marine diesel engines. The purpose of the research is: analysis of both basic and modern methods of modernization of the working process of the marine diesel engine, with the further possibility of their systematization and grouping in the form of a structural diagram; implementation of the collected and analyzed information in the form of the structural diagram of methods for modernizing the working process of the marine diesel engine. The research of both modern approaches and basic methods of modernization of the working process of the marine diesel engine is carried out by an analytical method followed by implementation into the block-diagram. A block diagram of the classification of modern methods for improving the working process of marine diesel engines is obtained. The results obtained allow us to conclude that the proposed block diagram makes it possible for the user to easily select the method of interest for modernization of the ship power plant operation with its further detailed study. There are uniqueness and novelty of the block diagram associated with the use of new topical methods for improving the diesel engine.