The intermediate frequency furnace is a power supply device that converts 50Hz AC power into intermediate frequency (300Hz to 100Hz) power, and then converts the three-phase AC power into DC power, and then converts the DC power into adjustable intermediate frequency current, which flows through capacitors and induction coils. Generate high-density magnetic force lines, cut off the metal material in the induction coil, use the principle of electromagnetic induction to generate a large eddy current of the metal material, heat the metal material, and smelt it.
The medium frequency induction furnace is a discrete system load. During the operation process, harmonic currents are introduced into the power grid, causing pulse current voltage on the characteristic impedance of the power grid, causing voltage fluctuations in the power grid, and affecting the quality of the power supply system and the operation safety of equipment. Since the commercial power supply of the intermediate frequency furnace becomes an intermediate frequency through the rectification frequency converter, the power grid will generate a large number of harmful high-order harmonics during operation, which is one of the largest high-order harmonic sources in the power grid load.
Five characteristics of intermediate frequency furnace
1. Save money
Faster heating, high productivity, less air oxidation carburization, saving raw materials and costs, and prolonging the service life of abrasive tools.
Because the principle of the intermediate frequency induction furnace is electromagnetic, the heat generated by the intermediate frequency induction furnace is generated by the steel itself. Ordinary workers can carry out the continuous work of the forging task within ten minutes after using the intermediate frequency induction furnace, without the need for furnace manufacturing. The workers started the furnace firing and sealing work in advance. Because this heating method heats up faster and has less oxidation, the oxidation ablation of intermediate frequency heating steel castings is only 0.5%, the oxidation ablation of gas furnace heating is 2%, and the raw coal furnace exceeds 3%. The intermediate frequency heating process saves Raw materials, compared with raw coal furnaces, one ton of steel castings saves 20-50KG less stainless steel plates. Its raw material utilization rate can reach 95%. Because the heating is uniform and the temperature difference between the core surface is small, the service life of the forging die is greatly increased during forging. The forging roughness is lower than 50um, and the processing technology is energy-saving. The intermediate frequency heating can save energy by 31.5%-54.3% compared with oil heating, and the gas heating Energy saving 5%-40%. The heating quality is good, the scrap rate can be reduced by 1.5%, the output rate can be increased by 10%-30%, and the service life of the abrasive tool can be extended by 10%-15%.
2. Environmental protection points
Excellent office environment, improve the office environment of employees and corporate brand image, zero pollution, energy-saving.
Compared with coal stoves, induction heating furnaces can no longer be smoked by coal stoves under extreme heat, which can meet the regulations of the Environmental Protection Agency. In addition, it can shape the external brand image of the company and forge the industry development trend of the manufacturing industry. Induction heating is the heating of electric furnace energy from room temperature to 100°C, the power consumption is less than 30°C, and the consumption of forgings is less than 30°C. Partition method of forging consumption
3. Heating fruit
Uniform heating, small temperature difference between core and surface, high temperature control accuracy
Induction heating generates heat in the steel itself, so the heating is even and the temperature difference between the core and the surface is small. The application of temperature control system can correctly control the temperature, improve product quality and pass rate.
4. Rate
The intermediate frequency furnace heats up faster, the melting furnace iron only uses electromagnetic energy not exceeding 500 degrees, and the melting is more complete and rapid.
5. Safety performance
The remote monitoring system of intermediate frequency electric furnace is selected, which is suitable for industrial production environment. Strong anti-interference ability and high safety factor. There is no wire connected between the operating device and the controlled device, that is, remote control. For all complicated operations, press the keys of the remote control from a distance. After receiving the instructions, the intermediate frequency electric furnace can complete the corresponding operations step by step according to a good process. Because the electric furnace is a high-voltage electrical appliance, it is not only safer, but also can avoid damage to the electric furnace due to panic caused by operating errors.
Why does the intermediate frequency furnace generate harmonics
Harmonics will seriously endanger the safe operation of the power grid. For example, harmonic current will cause additional high-frequency vortex iron loss in the transformer, which will cause the transformer to overheat, reduce the output volume of the transformer, increase the noise of the transformer, and seriously endanger the service life of the transformer. The sticking effect of harmonic currents reduces the constant cross-section of the conductor and increases the loss of the line. Harmonic voltage affects the normal operation of other electrical equipment on the grid, causing operational errors in automatic control equipment and inaccurate measurement verification. Harmonic voltage and current affect the normal operation of peripheral communication equipment; transient overvoltage and transient overvoltage caused by harmonics damage the insulation layer of machinery and equipment, resulting in three-phase short-circuit faults and damage to transformers; harmonic voltage and The amount of current will cause partial series resonance and parallel resonance in the public power grid, resulting in major accidents. In the whole process of inverter power supply, the first DC stabilized power supply is a square wave switching power supply, which is equivalent to the accumulation of sine waves with many high-order pulse currents. Although the post-stage circuit needs a filter, the harmonics cannot be completely filtered out, which is the cause of harmonics.
Harmonic power of intermediate frequency furnace
The output power of the intermediate frequency induction furnace is different, and the relative harmonics are also different:
1. The natural power of the high-power intermediate frequency furnace is between 0.8 and 0.85, the reactive power demand is large, and the harmonic content is high.
2. The natural power of the low-power intermediate frequency furnace is between 0.88 and 0.92, and the reactive power demand is small, but the harmonic content is very high.
3. The net side harmonics of the intermediate frequency furnace are mainly 5th, 7th and 11th.
Harmonic control method of intermediate frequency furnace
Single-tuned filters of 5, 7, 11 and 13 times have been designed. Before filter compensation, the power factor of the customer’s intermediate frequency induction furnace melting link is 0.91. After the filter compensation equipment is put into operation, the maximum compensation is 0.98 capacitive. After the filter compensation equipment is put into operation, the total operating voltage distortion rate (total harmonic distortion value) is 2.02%. According to the power quality standard GB/GB/T 14549-1993, the working voltage harmonic (10KV) value is lower than 4.0%. After performing filters on the 5th, 7th, 11th and 13th harmonic currents, the filter rate is about 82∽84%, which exceeds the control value of our company’s industry standard. Compensation filter effect is good.
Post time: Apr-13-2023