What are the differences between thyristor and IGBT modules used in intermediate frequency power supplies?

Simply put, a thyristor (KGPS) is a semi-controlled device; it conducts when a positive voltage is applied and a gate voltage is applied simultaneously, and turns off when the voltage is reversed. An IGBT, on the other hand, is a fully controlled device; its on/off state can be controlled solely by its gate.

Thyristors have very low switching speeds, while IGBT have very high switching speeds. IGBTs can be controlled by pulse width modulation (PWM), while thyristors cannot. They can only be used for phase-shift triggering.

1. Thyristor intermediate frequency power supplies, also known as KGPS, have the advantages of mature technology, reliable quality, and low price. The disadvantages are that their electrical efficiency is 10%~20% lower than that of IGBT intermediate frequency power supplies. Additionally, the harmonics in the rectifier section can affect the user's power grid system, and in severe cases, can damage other equipment within the grid.

2. IGBT intermediate frequency power supplies: These power supplies have a relatively short development cycle in China. Their advantages include high electrical efficiency, generally exceeding 90%, resulting in 10%~20% energy savings compared to thyristor power supplies, with minimal impact on the power grid. The disadvantage is that their production cost is higher than thyristors, leading to a higher price. However, considering the long-term energy savings, purchasing an IGBT power supply is quite worthwhile, as the annual electricity savings can easily buy one or two more such units. With the increasing maturity of domestic component production, it is believed that cost reductions will be achieved in the near future. Figure 1 shows the Japanese-imported IGBT module used in Nastar electric furnaces.

3. In terms of size, KGPS (thyristor-controlled silicon controlled rectifier) intermediate frequency power supplies are larger than IGBT intermediate frequency power supplies. Most IGBT devices operate at frequencies above 10kHz, while thyristor devices operate at frequencies below 10kHz.

4. Thyristor-controlled (KGPS) intermediate frequency power supplies have lower frequencies but can achieve higher power outputs. IGBT intermediate frequency power supplies, due to their higher frequencies, generally have lower power outputs. Therefore, their use is limited in certain fields.

Technology is constantly evolving, and nothing is absolute. Currently, there are attempts to develop high-power heating devices using IGBT power supplies. It seems there are induction heating devices with IGBT power supplies reaching 1000kW and frequencies of 50kHz.