Application of Frequency Control Techniques for Hot Tensile Testing in Induction Heating

Abstract

This paper proposes the frequency control technique using a half-bridge resonance inverter for hot tensile testing in induction heating. The technique involves power regulation, high frequency pulse, frequency adjustment, and pulse generator controller based on the dsPIC33FJ16GS404 chip IC. Significantly, the inverter is controlled by two sections. Throughout the heating cycle, the first controller retains the inverter's operating frequency slightly above the resonant frequency, while the second keeps the phase angle of the current and voltage output in check to control the output power at a level suitable for changes in the tensile parameter workpieces. As a result, the inverter improves the efficiency of the prototype, which has 1.5 kW input power. Furthermore, it can heat three different sizes of steel workpieces for hot tensile testing, with diameters of approximately 3, 5, and 10 mm and lengths of approximately 50 and 70 mm, respectively.