China's IF furnace industry is developing rapidly and the domestic equipments are close to the highest level in the world. A typical application is 1-tow-2 frequency conversion furnace, i.e. one rectifier with two inverter drives two same-sized electric furnaces, which can make a variable frequency power supply flexibly assigned to two electric furnaces, namely the high power allocated to the melting furnace, the remaining small power to the holding furnace, so as to realize "one furnace melting + one furnace insulating", make the electric system has the capability of continuous production of liquid iron. The following is the summary of the energy saving technology of the IF induction furnace.
Temperature control technology
IF melting furnace adopts CPU calculation program, using sophisticated software compiled by high-level language, the basic function is to constantly monitor IF power output, calculate the furnace capacity, also for continuous monitoring the environment temperature, cooling water temperature and flow, used to calculate the energy consumption of the furnace.
Constant power control technology
Series resonance power can adjust the working frequency of intermediate frequency power supply, realize the adjustment of the impedance. The change of the working frequency can avoid the direct change of the furnace impedance. When electric impedance is too low, the working frequency will be appropriately increased, in case it’s too high, the work frequency will be lowered. Through this adjustment, the furnace impedance will keep the same during the entire process, thus ensuring medium frequency power supply is always working under rated power.
Load matching study
Whether the load impedance matches properly will directly affect the rated power of the power supply. The design and calculation of induction coil (load) are very complicated, so it is not easy to design a satisfactory load coil. At present, many companies in China just ignore the secondary parameters, or make design from the experience of revising the formula, which has a big error.
High power factor and low harmonic
The new generation power supply must be high power factor with low harmonic. At present, the developed technologies include: multiple rectifier technology, fully controlled power tube plus matrix control or PWM control technology, series line, chopper technology and so on. That at the same time, leads to the development and production of harmonic filter and power factor compensation detuning device.
Energy conservation and emission reduction
The electrical efficiency of a well-designed medium frequency induction melting furnace can reach above 78%. As a result, under the existing technical approaches it is unlikely to get a big improvement of the melting efficiency for the induction furnace. To achieve substantial energy conservation and emission reduction, we need to work on sensors and furnace charge system, try to break through the existing framework and establish a new design model so as to increase the system efficiency of electricity to more than 90%.