High power factor, low harmonics. When the induction heating power supply has the best power factor, it can reach 0.95 , and it is often operated between 0.85 and 0.9 . In addition, there are inevitable harmonics, which constitute a certain pollution to the power grid. The greater the power supply, the more prominent this problem. The new generation of power supplies must be high power factor, low harmonic power supplies. The technologies developed now include: multiple rectification technology, full control power tube plus matrix control or PWM control technology, series circuit, chopping technology, etc. At the same time, it also gave birth to the development and production of harmonic elimination device for power supply harmonics and power factor compensation.