AC-AC pulse converter for the induction heating applications

As is known, the most useful power sources for induction heaters are semiconductor converters. The operating frequency range, which is used for induction heating, is about 0.5-50 kHz. In each specific case the operating frequency depends on the volume of the heated block and on the character of the technological process. Initially, since the electrical machine frequency converters have been used for such induction heaters, the form of the load voltage (current) was actually a sine wave. After the introduction of electronic frequency converters the sine wave form traditionally was conserved, in spite of the fact that modern power electronic converters permit the production of various forms of output voltage and current, including the pulse form. In these cases useful effects can be obtained both in the power supply and in the technological process. However, comparative research of the temperature distribution in a material heated by the sine wave current or by the pulse current shows that the pulse current is more suitable for the heating process. In addition, the pulse current converter for such heating, proposed in this paper, is simpler and has the following advantages: it has a close to unit power factor, soft commutation of the controlled switches, and wide range of output power. It also ensures the simplicity and reliability of a control system.