35kV Oil-immersed Electric Furnace Transformer

35kV Oil-immersed Electric Furnace Transformer

35kV Oil-immersed furnace transformers designed to provide power for various electric furnaces. Industrial electric furnace transformers can be roughly divided into three categories: resistance furnace transformers, electric arc furnace transformers, and induction furnace transformers.

Structural features

1. Iron core

The core of the shell-type electric furnace transformer is a frame structure with all bevel joints. Its core width is narrow, heat dissipation conditions are good, and the structure is simple.

2. Winding

The winding of the shell type electric furnace transformer is a rectangle with the same cross-sectional shape as the core column. The low-voltage winding is made of a whole copper plate, with good heat dissipation conditions, and has a welded structure; the high-voltage winding has a pie structure. The winding arrangement is always staggered. The high-voltage line segments and low-voltage line segments in each group should have equal magnetic potential, and their radial dimensions should be basically equal. Theoretically, place the low-voltage line segments at both ends because the insulation distance to the core is small. However, in order to make the short-circuit impedance of the transformer smaller, multiple magnetic flux leakage groups are needed to meet the requirements. Placing low-voltage line segments at both ends will limit the number of magnetic leakage groups, so high-voltage line segments are sometimes placed at both ends. During the voltage regulation process, in order to make the line segment configuration symmetrical and ensure the balance of the magnetic potential, multiple voltage regulation line segments are usually connected in parallel to ensure that the impedance of each magnetic flux leakage group is equal and the current of each low-voltage line segment is also equal.

3. Cooling method

Shell-type electric furnace transformers generally adopt forced oil-guided circulation, forced water cooling or forced oil-guided circulation, and forced air cooling. Since a partition can be easily set between the oil tank and the body of the shell-type transformer, the cooled transformer oil is forced to flow through the coils, the oil flow is uniform, the temperature difference between each part is small, and the heat dissipation effect is good, which can reduce the hottest point temperature by about 5°C and increase the additional overload capacity of the transformer.

4. Oil tank

Since the windings of the shell-type transformer are completely shielded by the core, the possibility of damage by external forces is small, so an oil tank of suitable shape can be used according to the shape of the body, thereby greatly reducing the size and weight of the transformer.

Advantages

1. Small mechanical force and good strength

Theoretical calculations show that the radial electromagnetic force of shell-type transformers is very small. Although the axial electromagnetic force is relatively large, it can be significantly reduced when there are more leakage magnetic groups. The windings of shell-type transformers are completely surrounded by insulating parts, and the iron core surrounds them. The iron core and the oil tank are clamped with wooden struts, and the entire body is firmly fixed. The short-circuit force is directly transmitted to the oil tank through the insulating parts and the iron core. Unlike the core-type structure, the winding support surface is small, so the mechanical strength of the shell-type transformer is high.

2. The winding has strong impact resistance

Because the shell-type transformer winding has fewer coils and large radial dimensions, the capacitance between coils is large, but the capacitance to the ground is small. Therefore, when the impulse voltage acts on the shell-type transformer, the starting voltage is basically linearly distributed, and the voltage gradient is greatly reduced. At the same time, due to the large inherent capacitance of the shell-type transformer, the oscillation time of the winding voltage is prolonged, and the transient voltage has decayed before the winding reaches the amplitude. Therefore, the shell-type transformer winding has a good performance in withstanding overvoltage shocks.

3. Low impedance

Each phase of the shell-type transformer can be divided into several leakage magnetic groups, and the radial size of the coil is large, the impedance can be designed to be 2%-3%, and its mechanical force and load loss are also small. Since the reactive power of the transformer is greatly reduced, the power factor of the electric furnace naturally increases.

4. Phase-splitting voltage regulation has no effect on the magnetic circuit

Since the three-phase magnetic flux of phase-splitting voltage regulation is asymmetric, the core-type transformer must use a five-column iron core. However, in the iron core of the shell-type transformer, each phase already has an independent magnetic circuit, and the asymmetry of the magnetic circuit does not affect the design of the iron core.

5. Short leads and easy impedance balance

The line end leads and tapping lines are led out as short as possible on the upper part of the winding, and the low-voltage winding leads can be of the same length, thereby eliminating the impedance imbalance of the low-voltage leads and reducing the power transfer during furnace operation.

6. Low loss

In engineering, the proportion of additional loss in load loss reflects the technical performance and economic performance of the transformer to a certain extent. The additional loss of the shell transformer is smaller than that of the core transformer of the same specification.

Technical Specifications

Note:

1. Due to the continuous updates of products, there may be some changes in the outline dimension and weight in the table. Please refer to the outline dimension diagram provided when placing an order.

2. Customized production can be carried out according to the customer's drawings and technical parameters.

Why choose BEYONDT?

1. We are an experienced manufacturer. We have 16 years of industry experience, from R&D to production.

2. We are a manufacturer that values quality and service. We always believe that quality and service are the life and soul of an enterprise.

3. We have the ability to provide customers with the best customized services, because our production lines and personnels are fully equipped.