Series and Parallel Connections: Induction heating power supply inverters mainly consist of parallel inverters and series inverters. A series inverter output can be equivalent to a low-impedance voltage source. When two voltage sources are connected in parallel, differences or fluctuations in their amplitude, phase, and frequency will lead to large circulating currents, resulting in severe current unevenness in the inverter devices. Therefore, parallel inverters face difficulties in parallel expansion. In contrast, for parallel inverters, the large DC reactor at the inverter input can act as a current buffer between the parallel inverters, allowing sufficient time for the AG/DG or DG/DG links at the input to correct DC current deviations, achieving multi-unit parallel expansion. The use of parallel inverter structures for transistorized ultra-high frequency and high-frequency current applications is largely due to the ease of modularization and large-capacity scaling of parallel inverters.
The loads of induction heating power supplies are diverse, and the power inverter and load are an organic whole. Generally, a matching transformer is used to connect the power supply and the load inductor. Matching transformers for high-frequency and ultra-high-frequency power supplies are undergoing further optimization and improvement in terms of magnetic materials and winding structures. Simultaneously, from a circuit topology perspective, three passive components can replace two passive components, eliminating the need for a transformer and achieving efficient and low-cost matching.
Induction heating power supplies using thyristors, transistors, and vacuum tubes can all be produced domestically. Thyristor power supplies have been produced and used for many years. IGBT power supplies are increasingly adopted by users due to their greater advantages. IGBT power supplies offer high efficiency and low voltage, but are more expensive and are gradually replacing vacuum tube high-frequency power supplies. Portable small high-frequency power supplies are widely used domestically due to their low price and convenience, and have even entered the international market.