Проблемы электродинамических усилий в индукционных нагревателях

Abstract

Problems are considered related to electrodynamic forces in the powerful induction heaters of industrial and medium frequency. The methods are given for calculating the forces acting on the heated blanks, inductive coils, and magnetic cores. One of the methods is based on the calculation of the total ponderomotive force acting on the current-carrying conductors and ferromagnetic bodies. To implement these methods, general-purpose computer-aided engineering software based on the finite element method and suitable for building electrothermal models is required. Building of such models is a rather laborious process, and the calculations take a significant amount of time, which does not allow the required number of calculations to be carried out within a reasonable time. Other methods are based on the calculation of the partial derivative of reactive power by the required coordinate. Thus, the corresponding projection of the force on the given axis is calculated. In combination with the subject-oriented 2DELTA coupled electrothermal software, this approach allows to perform the required number of calculations with a suitable for practice of induction heating design accuracy and with significantly less time. Comparative analysis was carried out related to the safety of some types of industrial induction installations used for heating various metals. The technological processes of induction heating of copper, aluminum and some steel grades are considered. The main parameters influencing the negative impact of electrodynamic forces are shown. In particular, when analyzing the axial component of such a force, it was established that the force of friction of the heated ingots against the guides has a significant negative effect. In the case of heating of ferromagnetic ingots, the direction and magnitude of the electrodynamic force are also influenced by the thermal regime. The methods are proposed for solving the problems of ensuring electromechanical safety in the design and tests of induction installations.