Furnance Transformer
The furnace transformer, also known as the smelting transformer, is a special power transformer mainly used for smelting metals such as steel. It can withstand ultra-large current loads and endure repeated high mechanical and thermal stresses caused by electric arcs. Typically, the primary voltage of the electric furnace transformer does not exceed 72.5 kV. The transformer can handle currents ranging from several thousand to tens of thousands of amperes. Generally, it has a large capacity and comes in two designs: split type and integrated type. The electric furnace transformer uses carbon rods as electrodes and is commonly employed in the electric furnace smelting of special steel, white corundum, electrolytic aluminum, and other materials.
Benefits of Furnance Transformer
High efficiency
Furnace transformers exhibit high efficiency, effectively converting high voltage to the required low voltage, thereby reducing energy consumption.
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Precise control
Furnace transformers feature precise voltage control capabilities, providing stable voltage output according to furnace heating requirements.
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High reliability
Designed and manufactured with specialization, furnace transformers offer high reliability and durability, capable of long-term stable operation.
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Perfect product system
Furnace transformers are applicable to various types of furnaces, including induction furnaces, arc furnaces, and resistance furnaces, with a wide range of applications.
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High safety
Equipped with multiple safety protection devices, furnace transformers effectively prevent overload, short circuit, and other electrical faults, ensuring the safety of equipment and personnel.
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The working of the furnace includes charging the electrode, meltdown period and refining. The light and heavy scrap in the large basket is preheated with the help of the exhaust gas. For speeding up the slag formation, the burnt lime and spar are added to The charging of furnace takes place by swinging off the roof of the furnace.
According to your needs, the hot metal charging all takes place. Then next comes the meltdown period. The electrodes are moved down into the scrap in this period. Them the arc is produced between the electrode and metal by considering the protection aspect, low voltage is selected for this. After the arc is shielded by electrodes, the voltage is increased for speeding up the melting period.
During this process, carbon, silicon and manganese get oxidized. The lower current is needed for the larger production. The heat is lost and it is also less. The process of melting down can be fast by deep bathing of the electrodes.
The process of refining starts at the time of melting. Removal of sulfur is not essential for the single oxidizing slag practice. Only phosphorous removal is needed in this. But in the practice of double slag, both the removable of oxidizing slag is done. Next, with the use of ferromanganese and aluminium or ferrosilicon, this gets deoxidized.
Types of Furnace Transformer
In many industrial applications arc furnace is used for example in the steel industry they are used to smelting scrap iron and for refining steel. They are also used for other applications such as smelting glass and ceramics, manufacturing and refining of many materials. Electric arc furnace can be either AC or DC and the power ratings of these transformers are 20 – 200MVA. Reactors are used to smoothen the fluctuations, either in the same tank or in a separate unit.
Ac arc furnace transformer can be used for long arc and short arc operations. These types of electric arc furnace transformers are used for many different furnace processes and applications. These types of transformers are used for steel furnaces, ladle furnaces and smelting of other materials steel arc furnace does its operation under severe conditions. With regard to frequent over-voltages and over-currents generated by the short circuits in the furnace and the operation of the HV circuit breaker. They have cyclic loading but in case of other applications loading is continuous at high utilization.
DC furnace transformer needs to withstand the stresses of furnace operation and it also needs to withstand other stresses which are related to the rectifier operation. This transformer behaves as a rectifier transformer for furnace operation. The HV side needs to be protected from frequent switching over-voltages. Most large DC furnaces are made for steel production. The use of the thyristor rectifier for the conversion to DC normally reduces the requirement for on-load voltage regulation of the furnace transformer. The step voltage is larger than the AC voltage, and a no-load tap changer is adequate in many applications.
The Role Of Furnace Transformers In Industrial Process
A furnace transformer is a specially designed transformer which is used in industrial furnaces to provide the necessary voltage to generate heat and melt metal components and other associated applications. They are designed to handle extremely high temperatures and heavy loads which applies to any furnace-related operation. Here are some of its key roles in any industrial process:
Voltage transmission: The main function of this transformer is to step up or step- down voltage levels as per the furnace requirement. The voltage level at which it operates is much higher than other transformer variants, making it durable and resistant to extreme heat.
Power distribution: Once the required voltage level is achieved from the power source, it facilitates the distribution of power to different sectors of the manufacturing plant, such as electric arc, induction furnace, and other heavy machinery. It ensures a stable power supply to all connected devices, optimising output and minimising downtime.
Load management: Industrial furnaces are designed to manage heavy loads during operations. It regulates the flow of electricity to meet the specific demands of the furnace without causing overload or any other form of instability in the electrical setup.
Voltage regulation: The voltage level needs to be maintained within a specific range for the furnace to operate optimally. Any form of fluctuation or anomaly is quickly adjusted, ensuring a steady and controlled supply of power throughout the operation.
Safety measures: Furnace transformers come with an array of safety features such as overload protection, short-circuit inhibitors, temperature monitoring, etc. These mechanisms protect the transformer and the connected furnace devices from any form of electrical fault.
Efficiency: Efficient transformation of voltages and management of electrical faults ensure the device runs optimally, conserving energy and reducing costs. It helps in reducing power losses, improves system stability, and improves the overall lifespan of all concerned devices in the electrical system.
Automation: With improved AI and telematics, modern-age transformers are also being integrated with automated systems that help in conducting various tasks remotely. This includes remote monitoring, diagnostics, operations, and analytics to name a few.
While the main purpose of a furnace transformer is clearly defined, its overall role in any industrial role can be moulded to the needs of the specific industry. It is of utmost importance to consider all the technical specifications that come into play to finalise the right furnace transformer which can contribute towards overall productivity.
Design Features of Furnance Transformers
Voltage taps and core design
Electric furnace transformers typically include multiple taps to adjust the secondary voltage. Due to the high current and few effective turns in the low-voltage winding, taps are often set in the high-voltage winding. The high-voltage winding requires more turns to provide the necessary voltage range at the secondary.
The core flux density varies with each tap due to different primary turns for each secondary voltage. The largest secondary voltage determines the core size, while the smallest secondary voltage influences the total number of primary turns. Consequently, the secondary voltage range significantly impacts the transformer’s weight and cost.
Reactance characteristics
The range of secondary voltage affects the reactance of the transformer. In a well-designed transformer, the reactance should vary inversely with the square of the secondary voltage. Typically, the reactance should not exceed 15%. A larger tap range may complicate the coil arrangement, while a smaller tap range results in a more compact transformer.
Coil arrangement
Coils should be arranged to ensure that the primary tap positions equally affect the reactance of each multi-coil in the low-voltage winding. A common approach is to wind each high-voltage coil fully and connect all coils in parallel in multiple groups. Taps are taken from the center of each winding, and corresponding taps are connected in multiple ways and switched quickly by a voltage regulator.
Transformer construction
The transformer tank, cover, and coil clamping structures are generally made of steel. Given the high current requirements, care must be taken in arranging busbars and leads to avoid loss concentration and heating of surrounding magnetic materials due to leakage flux. Busbars should be subdivided according to coil arrangement and staggered to ensure opposing current polarities in adjacent busbars.
Three-phase connections
Most large arc furnaces use a three-phase power supply, and it is common practice to employ a three-phase transformer with a delta connection for the low-voltage winding. Traditionally, a delta connection inside the transformer was used, but this often led to excessive losses. Nowadays, staggered busbars are passed through the transformer cover, and the delta connection is outside the transformer. Suppose the distance to the electric furnace is significant. In that case, busbars should be placed close to the furnace after leaving the transformer to minimize losses and avoid heating of nearby magnetic materials.
Cooling systems
Water-cooled transformers are preferred for large electric furnaces due to cost and space savings, and because there is often an ample supply of cooling water available for both the furnace electrode rack and the transformer. If the water quality is questionable, naturally cooled transformers are used instead.
Dust protection
Electric furnace transformers are often installed in dusty environments. To prevent dust ingress, transformers must be well-sealed. Properly designed stuffing boxes around each busbar can effectively prevent debris from entering the transformer.
Reactance requirements
A key characteristic of arc furnaces is that the arc resistance decreases as the current increases, which can cause instability unless a sufficient constant impedance is connected in series with the supply voltage. For large arc furnaces, the inherent reactance of the transformer is usually adequate. For smaller arc furnaces, additional reactance may be necessary, either by designing the transformer with higher reactance or by adding a separate reactor in series. The transformer’s inherent reactance should not exceed 10% to 15%, and this value is fixed once selected. If a separate reactor is used, it should include taps to allow for adjustment of reactance as needed.
During the storage, transportation or operation and maintenance of transformer insulating oil, if the oil quality is poor or there are too many impurities or moisture, the insulation strength will be reduced. When the insulation strength is reduced to a certain value, the transformer will be short circuited and cause electric spark, arc or risk temperature. Therefore, the oil quality of the transformer shall be checked regularly during operation, and the unqualified oil shall be replaced in time.
In order to avoid the aging damage of the iron core insulation layer of the electric furnace transformer: the aging of the iron core insulation layer or the damage of the fastening bolt sleeve will lead to large eddy current in the iron core, thus causing eddy current. Long time heating of iron core will lead to insulation aging. To avoid accidental damage to insulation during maintenance: when checking and repairing the hanging core of transformer, please pay attention to the maintenance of coil or insulating sleeve. If scratch damage is found, please dispose of it in time.
The poor touch of the internal connector of the coil, the connection point between the coils, the contact leading to the upper and lower pressure side bushing and the open fulcrum of the tapping will lead to partial overheating, insulation damage and short circuit or short circuit. Open circuit. The high-temperature arc generated at this moment will divide the insulating oil, produce a large amount of gas and add pressure to the transformer. When the pressure exceeds the maintenance setting of the gas circuit breaker without tripping, an explosion will occur.
Assuming that the furnace transformer coil or load is short circuited, the transformer will bear a considerable short-circuit current. Assuming that the maintenance system has shortcomings or the maintenance setting is too large, the transformer may be burned. Therefore, the device should be installed for reliable short-circuit maintenance. Adhere to good grounding: for the low-voltage system connected to zero in operation and maintenance, the neutral point on the low-voltage side of the transformer shall be directly grounded. When the three-phase load is unbalanced, the current will appear on the zero line. When the current is too large and the touch resistance is large, the high temperature will appear at the grounding address and light the surrounding combustible materials.
The partial discharge of the transformer is small, and together, it has high electrical strength under the same insulation scale. Even if it is lit by an open fire, it will extinguish itself. It does not contain any toxins and will not release harmful gases even after combustion. The combustion flue gas temperature is not high and the transparency is high. In addition, it will not cause damage to personnel, equipment and environment during manufacturing, transportation, storage and operation.
Certifications
Our Factory
Yawei Group has more than 180 engineering and technical person , more than 1200 employees, covering an area of 240,000 square meters.
We have strong production capacity and built a highly efficient marketing team. The products include 110kvpage-3-5220kv and 500kv ultra-high voltage transformers, 35kv and below dry-type transformers, oil immersed transformers, amorphous metal transformer, wind and solar storage new energy transformers, prefabricated substation and special transformers such as reactors, electric furnace transformers, rectifier transformers,mining transformers, split transformers and phase shifting transformers of various specifications. In order to assure the implementation of the advanced design and manufactural technology,some key equipments, moulds and tools had been replaced and improved with the latest technologies to meet the requirements of product quality.
FAQ
Jiangsu Yawei Transformer Co.,Ltd. is one of the most professional furnance transformer manufacturers and suppliers in China, specialized in providing high quality customized service. We warmly welcome you to buy high-grade furnance transformer made in China here from our factory.
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