Recently, we received some inquiries from customers about dry-type transformers and oil-immersed transformers.

As you may know, dry-type transformers are generally more expensive compared to oil-immersed transformers. But why? What’s the difference between them?

Let Catherine explain it to you today!

Installation Location

Dry-type transformers are preferred for indoor locations such as basements, floors, and rooftops, especially in areas with high human population density oil-immersed transformers are typically used in substations.

Application

Box-type transformers are generally used for indoor applications, while oil-immersed transformers are commonly used for outdoor temporary power supply.

Space Considerations

The choice between dry-type and oil-immersed transformers depends on the available space. oil-immersed transformers are suitable for larger spaces, while dry-type transformers are preferred in compact spaces.

Climate: oil-immersed transformers are more suitable for humid and hot environments. If dry-type transformers are used in such conditions, they must be equipped with forced air-cooling systems.

Appearance

Dry-type transformers have visible cores and coils, while oil-immersed transformers are enclosed and only the outer shell is visible.

Connection

Dry-type transformers mostly use silicone rubber bushings, while oil-immersed transformers often use porcelain bushings.

Capacity and Voltage

Dry-type transformers are mainly used for distribution purposes, with capacities up to 1600 KVA and voltages below 10 KV. oil-immersed transformers can handle all capacities and voltage levels, including high voltage such as 1000 KV.

Insulation and Cooling

Dry-type transformers use resin insulation and rely on natural or forced-air cooling, while oil-immersed transformers use insulating oil for insulation and heat dissipation through radiators or cooling fins.

Suitable Locations

Dry-type transformers are commonly used in fireproof and explosion-proof environments, often in large and high-rise buildings. On the other hand, oil-immersed transformers are typically installed outdoors with provisions for an "incident oil pit" in case of leaks or spills.

Load-Bearing Capacity

Dry-type transformers should operate within their rated capacity, while oil-immersed transformers have better overload capacity.

Cost

Dry-type transformers are generally more costly compared to oil-immersed transformers of the same capacity.

If you want to know more about transformer cores, especially hope to purchase some good transformer cores in China. Contact SHUNGE! We will be very glad to help!

 

Transformers use various types of cores, with the most common ones being E-type and C-type cores. What are the differences between these two types of cores? And in which applications are they commonly used? Today, SHUNGE will tell you all about it.

E-type and EI-type cores are widely used in the industry. One of their main advantages is that the primary and secondary windings can share the same core, resulting in a higher window utilization factor. The core also provides protection for the windings, making them less susceptible to mechanical damage. Additionally, E-type cores have a larger heat dissipation area and reduce magnetic field dispersion.

However, E-type cores also have some drawbacks. They tend to have larger magnetic resistance due to the presence of larger air gaps in the magnetic path, which reduces the overall performance of the magnetic circuit. Furthermore, E-type cores are prone to issues such as higher copper wire usage, greater leakage inductance, and susceptibility to external magnetic field interference.

 

C-type cores are manufactured by winding cold-rolled silicon steel strips, which are then subjected to heat treatment and impregnation processes to form closed cores. These closed cores are then split to create two C-type cores. The windings are then encapsulated within the cores, and a pair of C-type cores are assembled and secured together to form the transformer.

C-type cores can have very small air gaps, and they offer advantages such as smaller size, lighter weight, and higher material utilization.

So, how can we identify the type of transformer core used in a power supply?

1. Identification based on appearance:

E-type cores have a shell-like structure, with a core that wraps around the coils. They are commonly made of high-quality silicon steel sheets such as D41 and D42. C-type cores, on the other hand, are made of cold-rolled silicon steel strips and have a core-type structure.

2. Identification based on the number of winding terminals:

Power transformers often have two windings, a primary and a secondary, resulting in four terminal connections. Some power transformers may have an additional shielding layer between the primary and secondary windings for AC noise and interference suppression. In such cases, the shielding layer is grounded. Therefore, power transformers typically have at least four terminal connections.

3. Identification based on the stacking method of silicon steel sheets:

In E-type power transformers, the silicon steel sheets are interleaved, with no air gaps between the E-shaped and I-shaped sheets. The entire core fits together tightly. In contrast, audio input/output transformers have certain gaps between their E-shaped sheets, which serves as a distinguishing feature from power transformers. C-type transformers are generally used as power transformers.

Shunge Steel, founded in 2008 and headquartered in Lecong, Foshan, produces cores with features such as low iron loss, high magnetic permeability, and high saturation induction. Our cores find applications in various fields, including signal communication, power drive, traction, renewable resources, charging station power control, high-precision measurement and control, new energy vehicle battery management, power control, welding, and new energy vehicle motor control.

If you have any core requirements, please feel free to contact us.

Transformer cores are commonly made of silicon steel sheets. Silicon steel, a type of carbon with silicon content ranging from 0.8 to 4.8%, strong magnetic properties. silicon steel sheets for transformer cores allows for higher magnetic induction, leading to reduced size.

In practical, transformers work under current conditions, resulting in losses in both the resistance and the core. These losses consist of two components: hysteresis loss and eddy current loss.

hysteresis loss and eddy current loss

Hysteresis loss occurs due to the magnetic hysteresis phenomenon in the core material during the magnetization process. Silicon steel has a narrow hysteresis loop, which minimizes hysteresis loss and reduces heat generation in the core.

Why do we process silicon steel into laminated sheets instead of using a solid block? The answer lies in minimizing another type of iron loss called "eddy current loss." When alternating current flows through the winding, it generates a varying magnetic flux in the core. This changing flux induces eddy currents within the core material, resulting in heat generation. To minimize eddy current loss, transformer cores are made by stacking insulated laminations of silicon steel, creating a compact and efficient pathway for eddy currents with reduced cross-sectional area. Additionally, the silicon content in the steel increases its resistivity, further mitigating eddy current effects.

Typically, transformer cores are constructed using cold-rolled silicon steel sheets with a thickness of 0.2 to 0.5mm. These sheets are cut into elongated shapes and then stacked in a "E-shaped" or "C-shaped" configuration, depending on the specific needs. Thinner laminations and narrower interleaved sections result in better eddy current suppression, decreased temperature rise, and material cost savings.