The intermediate frequency furnace will generate a large number of harmonics during use. The harmonics will not only cause local parallel resonance and series resonance of the power, but also amplify the content of the harmonics and burn out the capacitor compensation equipment and other equipment. In addition, the pulse current will also cause faults in relay protection devices and automatic devices, which may lead to confusion in the measurement and verification of electromagnetic energy.
Power grid harmonic pollution is very serious. For the outside of the power system, harmonics will cause serious interference to communication equipment and electronic equipment, and harmonics are quite harmful to intermediate frequency furnace equipment. Therefore, improving the power quality of the intermediate frequency furnace has become an important part of the response.
The intermediate frequency furnace is a typical discrete power engineering load, which will generate a large number of advanced harmonics during the working process, also known as intermediate frequency furnace harmonics. Its harmonic weight is mainly 5, 7, 11 and 13 times. The existence of a large number of high-order harmonics will seriously endanger the safety and smooth operation of the power engineering and capacitance compensation equipment of the same busway. The six-phase transformer can offset the fifth and seventh harmonics generated by the intermediate frequency furnace, but if no corresponding suppression measures are taken, the system will amplify the harmonics, affect the stable operation of the transformer, and even cause the transformer to overheat and damage.
Therefore, when compensating for the harmonics of the intermediate frequency induction furnace, attention must be paid to the elimination of harmonics, so as to prevent the compensation equipment from amplifying the high-order harmonics. When the intermediate frequency load capacity is large, it is easy to cause tripping accidents at the high voltage end of the substation and harmonic interference of enterprises along the line. As the load changes, the average power factor of the general furnace cannot meet our company’s standard, and it will be fined every month.
Understand the hazards of high-frequency furnaces in the use of harmonic control, how to ensure the normal operation and service life of equipment, and improve efficiency.
First, Brief description of environmental protection and energy saving of parallel and series intermediate frequency induction furnace power supply circuits:
1. Compared with the series or parallel circuit, the current of the load circuit is reduced from 10 times to 12 times. It can save 3% of operating power consumption.
2. The series circuit does not require a large-capacity filter reactor, which can save 1% of power consumption.
3. Each induction melting furnace is independently powered by a group of inverters, and there is no need to install a high-current furnace switch for switching, thus saving 1% of power consumption.
4. For the series inverter power supply, there is no power concave part in the working power characteristic curve, that is, part of the power loss, so the melting time is significantly reduced, the output is improved, the power is saved, and the environmental protection and energy saving are 7%.
Second, the generation and harm of intermediate frequency furnace harmonics:
1. Parallel intermediate frequency electric furnace power supply system is the largest harmonic source in the power system. Generally speaking, the 6-pulse intermediate frequency electric furnace mainly produces 6 and 7 characteristic harmonics, while the 12-pulse inverter mainly produces 5, 11 and 13 characteristic harmonics. Typically, 6 pulses are used for small converter units and 12 pulses are used for large converter units. The high-voltage side of the two furnace transformers adopts phase-shifting measures such as extended delta or zigzag connection, and uses secondary double-sided star-angle connection to form a 24-pulse intermediate frequency power supply to reduce the impact of harmonics on the power grid.
2. The medium frequency induction furnace will generate a lot of harmonics during use, which will cause very serious harmonic pollution to the power grid. Harmonics reduce the transmission and utilization of electromagnetic energy, make electrical equipment overheat, cause vibration and noise, embrittle the insulation layer, shorten the service life, and even cause failure or burns. Harmonics will cause local series resonance or parallel resonance in the power supply system, which will increase the harmonic content and cause capacitor compensation equipment and other equipment to burn out.
When reactive power compensation cannot be used, a reactive power penalty will occur, resulting in an increase in electricity bills. Pulse current can also cause faults in relay protection devices and automatic devices, which may lead to confusion in the measurement and verification of electromagnetic energy. For the outside of the power supply system, the pulse current will have a serious impact on communication equipment and electronic products, so improving the power quality of the intermediate frequency induction furnace has become a top priority.
Post time: Apr-12-2023