There are three kinds of induction furnace commonly used: 1. Medium frequency generator set, 2. Silicon controlled static inverter, 3. Frequency multiplier
There are two types of medium frequency generator set: horizontal and vertical. The frequency of the output current of the medium frequency generator set does not change with the load. It has the advantages of strong overload capacity, reliable operation and convenient installation and maintenance. However, compared with the static frequency converter, it has the disadvantages of large noise, large vibration, large material consumption, bulky volume and low electrical efficiency (80-85%). The main circuit consists of inductor, capacitor, intermediate frequency generator and high (low) voltage switch. The medium frequency generator set consists of generator and motor. The working voltage of motor is divided into high voltage (6000V or 10000v) and low voltage (380V). High pressure is used for large capacity furnace and low pressure is used for small capacity furnace. All motors are squirrel cage asynchronous motors. The generator is driven by the motor and generates medium frequency current to supply the induction furnace.
In the circuit of SCR static inverter, the transformer depressurizes the three-phase power supply and supplies it to the inverter. In the inverter, the three-phase bridge semi controlled full wave rectifier is used first, and then the reactor is used for filtering to obtain the DC power supply. The DC power supply is transformed into the medium frequency power supply with variable frequency by the single-phase bridge inverter and supplied to the induction furnace.