THE AUTOTRANSFORMER METHOD OF CONNECTING THE INDUCTOR TO THE THYRISTOR CONVERTER

Abstract

The issue of the correct coordination of the inverter parameters with the load parameters in order to obtain the highest output power of the converter at the necessary margin of its stability is considered. In order to avoid impermiassibly high temperature drops in the radial direction of the workpieces, the specific power of inductors is limited, as a result of which it is expedient to perform them for a voltage of 500 ... 750 V and higher. In addition, high-frequency furnace capacitors for compensating the reactive power of the load are produced with a rated voltage from 375 to 1000 V, so the connection of the inductor to the inverter with a reduced output voltage has to be carried out according to the autotransformer circuit. In order to simplify the calculations, it is assumed that the power factor along the length of the inductor has a certain constant averaged value and does not depend on the distribution of the temperature field along the inductor. Based on this assumption, the dependence of the active resistance of the load on the number of turns of the inductor can be presented as a linear function for various transformation ratios. When matching the parameters of the inverter with the parameters of the load circuit, it is necessary not only to ensure full compensation, but also to select the value of the equivalent active resistance of the circuit in such a way that the inverter give the most power, and at the same time, the time provided for restoring the controllability of the thyristors must remain within acceptable limits. Therefore, the estimation of the value of the equivalent active resistance of the load circuit at various transformation ratios is necessary.