Method of Relative Magnitudes for Calculating Magnetic Fluxes in Electrical Machine
Oleg A. Zakharzhevskii
Introduction: The article presents the study results of the model of an asynchronous electric motor carried out by the author within the framework of the Priorities Research Program “Research and development in the priority areas of development of Russia’s scientific and technical complex for 2014–2020”.
Materials and Methods: A model of an idealized asynchronous machine (with sinusoidal distribution of magnetic induction in air gap) is used in vector control systems. It is impossible to create windings for this machine. The basis of the new calculation approach was the Conductivity of Teeth Contours Method, developed at the Electrical Machines Chair of the Moscow Power Engineering Institute (MPEI). Unlike this method, the author used not absolute values, but relative magnitudes of magnetic fluxes. This solution fundamentally improved the method’s capabilities. The relative magnitudes of the magnetic fluxes of the teeth contours do not required the additional consideration for exact structure of magnetic field of tooth and adjacent slots. These structures are identical for all the teeth of the machine and differ only in magnitude. The purpose of the calculations was not traditional harmonic analysis of magnetic induction distribution in air gap of machine, but a refinement of the equations of electric machine model. The vector control researchers used only the cos(θ) function as a value of mutual magnetic coupling coefficient between the windings.
Results: The author has developed a way to take into account the design of the windings of a real machine by using imaginary measuring winding with the same winding design as a real phase winding. The imaginary winding can be placed in the position of any machine windings. The calculation of the relative magnetic fluxes of this winding helped to estimate the real values of the magnetic coupling coefficients between the windings, and find the correction functions for the model of an idealized machine. Modeling in the MATLAB showed that the refinement model of the idealized machine makes the electromagnetic processes similar to the processes of the real machine.
Discussion and Conclusions: The use of the proposed correction functions does not require the alteration of the vector control systems. The correction functions make the Park’s and Clark’s transformations more exact. The model of machine becomes more accurate and the processes taking place inside it coincide with real machine processes. The control of the electric machine becomes more precise.
Keywords: magnetic fluxes, calculating magnetic fluxes, electric machine, Clark’s and Park’s transformations, method of relative magnitudes
For citation: Zakharzhevskii O. A. Method of Relative Magnitudes for Calculating Magnetic Fluxes in Electrical Machine. Vestnik Mordovskogo universiteta = Mordovia University Bulletin. 2018; 28(1):62–76. DOI: 10.15507/0236-2910.028.201801.062-076
Acknowledgements: The author thanks colleagues from the Institute of Electronics and Lighting Engineering of the National Research Mordovia State University for benevolence to the unusual author's approaches used for the study of an asynchronous machine. The author expresses a special gratitude to V. V. Afonin for participating in the research as far as possible and for his help in MATLAB modeling.
This work is licensed under a Creative Commons Attribution 4.0 License.