Method of Cylindrical Linear Induction Motor Equivalent Circuit Parameters Determination and Performance Calculation Algorithm

Abstract

Cylindrical linear induction motors (LIM) are currently used in many industrial applications. Task of modeling of electrical machine is of great importance for optimization of processes of design and manufacture of engines with optimal technical characteristics. Traditional approach of construction of mathematical models of asynchronous machines based on classical theory of electrical machines, in comparison with methods of field theory and numerical methods, is much simpler. Structurally cylindrical LIM are distinguished by the absence of transverse edge effects, which contributes to the use of the methods of the classical theory of electrical machines for construction of their mathematical models. In this paper proposes an analytical method of calculation of parameters of equivalent circuit and operating characteristics of cylindrical LIM. In work engine was studied, movable part of which is made in the form of solid steel bar with a copper coating. Equivalent circuits of linear induction motors of various designs (one-sided, two-sided, cruciform, cylindrical) are considered, and assessment of the possibility of their application for research motor is made. Work of cylindrical LIM on industrial mechanisms is characterized by relatively small value of working stroke. For such engines, it is difficult to carry out standard tests, in particular idle stroke test, in order to obtain data for calculation of parameters of the equivalent circuit. The paper proposes a method of experimental determination of parameters of the equivalent circuit. Stator active resistance is measured at direct current, and stator reactance is measured using out-of-rotor method. The remaining parameters of equivalent circuit are calculated according to short circuit experience and engine work mode without load (is taken as an idle stroke experience). It is shown that exact G-shaped equivalent circuit, when calculation of parameters of which active and reactive components of correction factor and active resistance of magnetization branch are taken into account, provides acceptable accuracy in determination of values of equivalent circuit parameters. Algorithm of calculation of work characteristics of cylindrical LAM based on equivalent circuit data is presented. Comparison of calculated and experimental data showed satisfactory results, error is not more than 7%. A new model for decomposition of the total power losses, which includes four components is proposed. Each of the components of the proposed model has a certain physical meaning due to the nature of electromagnetic processes in a three-phase four-wire system. Definitions to describe each of the proposed components are formulated. It is shown that each of supplementary components of the total loss power is proportional to the minimum possible loss power and to the square of the RMS value of the power, which is caused by its occurrence in three-phase four-wire power supply system, and it is inversely proportional to the mean square of the net power loss. The synthesized Matlab-model for verification of the four-component structure of power losses showed a high degree of its adequacy. The proposed model allows us to rethink the description of power losses in three-phase AC circuits and can be used in specialized measuring instruments for electrical networks monitoring. Using the information obtained in the monitoring process, it is possible to plan technical measures to reduce losses of electrical energy in the power supply system, as well as to estimate the capital costs of these measures.