Use of Mathematic Model of Direct Frequency Converter-Asynchronous Motor (DFC-AM) System for the Assessment of Energy Characteristics of the Electric Drive

In the article, on the example of electric drives of the main mechanisms of excavators with a bucket capacity of up to 10m3, as well as an electric drive of the hydraulic distributor of an ultra-high pressure press, the issues of increasing the speed of the working element, if they are equipped with frequency-controlled electric drives, are considered. In the described structure direct frequency converter (DFC), assembled on the basis of reversible thyristor TC converters, is set to the current source mode. At the same time, the efficiency of electricity consumption is achieved by hardware, when the current assignment signals are formed using a microprocessor generator of sinusoidal signals, and an automatic coordinate control structure is introduced into the DFC-AD electric drive control system. It is possible to achieve high reliability of production mechanisms only by using fully controlled AC electric drives with wide adjustment capabilities and high dynamic performance. The efficiency of electric energy consumption of the electric drive by the DFC-AM system is analyzed at the base of the results of calculating the AM phase currents on a mathematical model of the electric drive and analyzing them with oscillograms of real currents taken on a laboratory bench. Expressions of coefficients are given, with the help of which it is possible to characterize the volumes of energy consumption from the network and to estimate the influence of distortions from DFC voltages during the operation of valve converters on the power supply network. The obtained mathematical expressions of coefficients, allowing to estimate the quality of energy consumption by AC electric drives, can be used for comparative analysis of various power circuits while studying DFC-AM systems as the generalized energy objects.