Reducing power losses in axisymmetric electromechanical converters

Purpose - The aim of the paper is to find the effective methods of power loss reduction in axisymmetric electromagnetic devices and improve their dynamic parameters. As an example the linear tubular motor is considered. Design/methodology/approach - The elaborated algorithm has been applied to analyze the dynamic operation of axisymmetric electromagnetic devices, especially tubular linear induction motors. The mathematical model of transients includes: the equation of electromagnetic field, the equations of electric circuits and the equation of motion. The model is based on the finite element method. For the time-stepping, the Cranck-Nicholson scheme is applied. In order to include non-linearity, the Newton-Raphson process is adopted. Findings - In order to reduce the influence of eddy currents, it is suggested that the solid core should be equipped with one or several radial slots. In such a case, the radial component of eddy currents occurs near the slot and disturbs the axial symmetry of the system. However, when the width of the slot is small, the fields generated by the radial component of eddy currents on both sides of the slot practically cancel one another and the system can still be considered axisymmetric. Another solution given in the paper consists of replacing the cylindrical core with a system of flat laminated segments. In such a case, saturation of the ferromagnetic parts is greater than in the case of classical axisymmetric core. Originality/value - In the paper, new quasi-2D axisymmetrical field-circuit methodology for electromagnetic device dynamics analysis has been elaborated. Proposed constructional solutions enable one to reduce the power losses in the primary core by half and total losses by 30 percent.