The Ultimate Guide To Core Type Transformer
Transformers have a ton of configurations that need consideration to ensure that you find the best one for your needs. Among these designs, core construction is essential to the transformer's magnetic flux, voltage and current handling capabilities, and overall efficiency.
Daelim mainly produces core-type transformers. Daelim has a professional technical team, overseas marketing team, and local after-sales service team. No matter which country you are from, or which international standard design, power transformer, substation transformer, pad mounted transformer, 1 phase or 3 phase, Daelim transformer factory can fully satisfy. And it has advantages in delivery time and quality.
Different transformers use two main types of core construction: shell core design (shell type) and closed core design (core type). This FAQs guide will focus on the latter, as we discuss some of the most important questions and points people tend to ask about a core type transformer.
What is a core type transformer?
The structure in which the transformer core is surrounded by windings is called a core transformer. Because of its relatively easy assembly of windings and insulation, and simple structure, electrical transformers often use core type structures.
Learn more about Core Type Transformer
What is shell-type transformer?
The structure in which the transformer winding is surrounded by an iron core is called a shell-type transformer. Suitable for low voltage and low power transformers.
What are the Types of Transformer Core?
As mentioned earlier, a transformer has two types of core configurations: shell core design and closed core design, otherwise known as shell type and core type, respectively. The key distinction between these transformer core types lies in the placement of the cores and windings. Therefore, let's discuss them separately to understand the difference further.
In a shell-type transformer, the cores are placed outside the windings, while in a core-type transformer, the cores are, while in the latter, the cores wrap around the windings. The main benefit of a core type transformer is that it offers better mechanical stability than a shell type transformer.
There are four methods of connecting to the transformer's primary and secondary windings to make them appear symmetrical. Conventional magnetic circuit configurations, along with frequent wave combinations, will have a significant influence on transformer and power system performance.
Learn more: How Much You Know For The Different Types Of Transformers?
What material is used as a core of a transformer?
The iron core constitutes the magnetic circuit of the transformer. The transformer core material is mainly 0.35-0.45mm silicon steel sheet. The transformer core is composed of laminations--many thin strips of grain-oriented silicon steel. These laminations are electrically isolated from each other by thin coatings of insulating material. Even though these two parts are not physically touching, they are still connected by a magnetic force, which helps reduce the transformer's energy losses.
Because silicon steel is a super-permeable material, stronger electromagnetic induction can be generated in the current coil. Used as a transformer core material can reduce the size of the transformer, and the hysteresis loss and eddy current loss are small, reducing the heat generation of the transformer, and prolonging the service life of the transformer.
Whether it is a core-type transformer or a shell-type transformer, the most commonly used core material is silicon steel sheet.
Read more: How Do I Choose A 1500kva Transformer In 2023?
Core type transformer construction
The iron core of the core type transformer is generally placed vertically, the cross-section of the iron core is a graded cylindrical shape, and the winding surrounds the core column, so it is called the core type. There are many specifications of iron chips, and the requirements for binding and clamping are relatively high, but the matching cylindrical windings are easy to manufacture and have good stability when short-circuited.
Core type transformer construction mainly has the following two types:
Single phase core type transformer
There are two main types of single phase core type transformers: single-phase double-leg structure and single-phase single-leg side-yoke structure.
Single-phase double-leg transfromer
In the core type transformer of this structure, the iron core column and the iron pole have the same cross-section, and are stacked in an overlapping manner in the same vertical plane. Windings can be placed on the two iron core columns, and the windings on the two iron core columns can be connected in series or in parallel.
It has a simple and compact structure, less process equipment, but a large stacking workload. Suitable for small and medium-sized single-phase transformers. For example: single phase pole mounted transformer and single phase pad mounted transformer produced by Daelim, both belong to single-phase double-leg structure. The maximum voltage is 34.5kV, and the capacity is usually below 333kVA.
Single-phase single-leg side yoke
The core-type transformer with this structure has a core column in the middle and side yokes on both sides. The cross-section of the yoke is half of the cross-section of the core column. It is also called the center column core, and the additional loss is small. Compared with the single-phase double-column iron core structure, the width of the iron sheet can be reduced by half, so the height of the transformer can be reduced.
The winding is installed on the middle iron core column, but the voltage-regulating winding and the excitation winding can also be installed on the side yoke, but the stacking workload is relatively large, and it is suitable for large single-phase transformers and some special transformers.
Three phase core type transformer
Three phase core type transformer mainly has two types: three-phase three-leg structure and three-phase five-leg structure
Three-phase three-leg structure transformer
This structure has one more core leg than the single-phase two-leg type. The cross-section of the iron core leg and the iron yoke is the same, the magnetic flux in the three iron core legs is almost the same, and the phase difference between them is 120 degrees.
Each of the three-leg windings is a group of leads. It is a typical structure of a transformer and is the most widely used at present. It is widely used in large, medium, and small 3-phase transformers or some special transformers.
In this 3 phase core type transformer structure, the iron yoke has a rectangular yoke in addition to the commonly used circular yoke and D-shaped yoke. This kind of iron core yoke can reduce the overall height of the transformer, reduce the amount of silicon steel sheets, reduce the volume of the oil tank, reduce the cost of the transformer, and at the same time ensure that the transportation side of the transformer does not exceed the maximum specified by the national standard item road transport limit.
You may enjoy: 2500 kVA Pad Mounted Transformer
Three-phase five-leg structure transformer
This structure has an iron core column in the middle, side yokes on both sides, and the cross-section of the yoke is half of the cross-sectional area of the iron core column. Set the windings on the middle three core legs only.
Compared with the three-phase three-leg core structure, it can meet the requirement of reducing the core height of large transformers, so that the transformer can be transported smoothly, and also increases the manufacturing cost of the transformer. It is suitable for large three-phase transformers and some special transformers.
The 3 phase pad mounted transformer and skid mounted transformer provided by Daaelim, which connection group is YNyn0, are all 3 phase five-leg structures.
Application of Core Type Transformer
The application of core type transformer is very broad. Core type transformers have good mechanical properties, high reliability, small size, and low maintenance costs, so they are widely used in power transmission and distribution, industry, commerce, residential, renewable energy, battery energy storage, data centers, and oil and gas exploration.
Reading more: Different Transformer Types and Their Applications
Core type transformer winding
There are three types of core-type transformer winding: single winding, two-winding, and three winding
Single-winding transformer
s are also called autotransformers, and the primary and secondary windings are directly connected in series on the same winding.
Two-winding transformer
A two-winding transformer has two windings on the iron core, namely the primary winding and the secondary winding. There are many dual-winding Core type transformers on the market. Common pad mounted transformers and single phase overhead transformers for distribution lines are core type double winding transformers.
Three-winding transformer
Usually for transformers power rating above 5600kVA, it is possible to use three-winding transformers. Used to connect three different voltages, such a transformer is called a three-winding transformer. For example, in the power system, three-winding transformers are used between 230kV, 115kV, and 34.5kV.
Diagram of Core Type Transformer
The figure below shows the typical construction of a core-type transformer. As you can see, the primary and secondary windings are placed around the central laminated core. The figure also illustrates the different parts of a transformer.
Through this illustration, you can also see the motion of the flux. The magnetic flux first passes through the primary winding and then through the secondary winding in a counterclockwise direction.
Reading on: Let's know more about the construction of a three-phase transformer
Why is Iron Core Used in Transformer
Iron is the most popular choice for the magnetic core of all the materials used in transformers. This is because iron has a relatively high permeability which allows it to amplify the strength of the magnetic field. The strong magnetic field will then induce a voltage in the secondary winding.
The changing magnetic field triggers a changing potential difference in the secondary coil, producing an alternating current in the external circuit in the process. As a result, the iron core helps to transform the voltage from the primary winding to the secondary winding more effectively and efficiently.
In addition, iron is also relatively inexpensive and easy to obtain, which makes it the ideal choice for use in transformers. At the same time, iron also has a relatively high melting point which helps improve the safety of transformers in the event of overheating.
Read my article on The Ultimate Guide To 20 MVA Transformer
Advantages of Core Type Transformer
Core type transformers offer several interesting perks and advantages, such as:
Excellent Mechanical Ability
Core type transformers use cylindrical coils wound up over a symmetrical core. This results in a more balanced construction, which helps to reduce the mechanical stress on the transformer. As a result, core-type transformers can better withstand external forces and vibrations, making them ideal for use in industrial and commercial settings.
Prevents Iron Losses and Condensed Flux Leakage
The lamination in a core type transformer overlaps to create a "laminated core." This construction helps to prevent iron losses and condensed flux leakage, which can cause transformers to overheat. In addition, the overlapping configuration also ensures an accurate core thickness.
Efficient for High-Frequency Currents
The main function of a transformer is to convert high-frequency alternating current (AC) into direct current (DC). Since core-type transformers utilize several steel laminations, the eddy current losses are contained and reduced. As a result, core-type transformers are more efficient for high-frequency currents.
In addition, core-type transformers are protected by a non-conduction insulation material between their layers. This configuration further reinforces the transformer against the effects of high-frequency currents. While these laminations are more expensive and difficult to produce, their ability to make the transformer more efficient for high-frequency currents makes them well worth the investment.
Improved Cooling
The three-phase core type transformer features a greater surface area which helps to improve cooling. In addition, the increased surface area helps to dissipate the heat generated by the transformer more effectively, helping to improve its overall performance and longevity.
Try for free: The ultimate guide to ONAN transformers
Dissipates Heat More
Transformers are prone to overheat, which can cause extensive damage to the unit. The core type transformer's increased surface area helps to dissipate the heat generated by the transformer more effectively, helping to improve its overall performance and longevity.
In addition, the core type transformer winding is also better protected against overheating. The windings are located inside the transformer, where they are less likely to be exposed to external heat sources. This helps to improve the transformer's cooling ability further and prevent overheating.
Disadvantages of Core Type Transformer
Despite the many advantages of core-type transformers, there are a few disadvantages to consider as well, such as:
More Expensive
One of the main disadvantages of core-type transformers is that they are more expensive to produce. In addition, the increased surface area and the number of layers in a core type transformer make it more difficult and costly to manufacture.
However, the improved efficiency and performance of core-type transformers typically make them worth the extra cost. In addition, the increased durability of core-type transformers often means that they have a longer lifespan, which can help to offset the initial higher cost.
Frequent maintenance
Iron core transformers are usually used outdoors. If it is a special environment such as high altitude and corrosion-prone areas, it needs to have higher requirements on the shell, temperature rise, and insulation. During extreme weather conditions, its internal components, especially those made of metal, may be lowered. Regular maintenance and even replacement of parts are required.
Keep reading: Analysis of electric transformer noise problem
Can Be Noisy
Core type transformers and other dry transformers tend to be noisy as they produce audible noise emissions from the transformer's cooling fans. While the noise level can vary depending on the size and capacity of the transformer, it is something to keep in mind if noise is a concern.
Despite these disadvantages, core-type transformers still offer many advantages that make them popular for many applications. Core-type transformers can provide superior performance and durability when used in the right setting.
Distinguish Between Core Type and Shell Type Transformer
It's important to note that there is another type of transformer on the market, known as the shell type transformer. While both transformers serve the same purpose, you should be aware of a few key distinctions between the two types.
The main difference between the two types of transformers is their construction. Core type transformers are constructed with an overlapping arrangement of laminations, while shell type transformers are composed of a single piece of steel.
As a result, core-type transformers are more efficient for high-frequency currents, while a shell-type transformer design is more suitable for low-frequency transformers. In addition, the lamination in a core-type transformer helps to prevent iron losses and condensed flux leakage, which can cause transformers to overheat.
On the other hand, shell-type transformers are less expensive to produce and are easier to assemble. In addition, shell-type transformers typically have a smaller footprint, making them more suitable for use in limited spaces.
Another key distinction between the two types of transformers is their size. Due to their construction, core-type transformers are typically larger and heavier than shell-type transformers. As a result, core-type transformers are more difficult to transport and install. On the other hand, a shell-type transformer is more compact and lightweight, making it easier to install and transport.
Click here to check Daelim International Transformer Projects.
Core Type of Shell Type—Which is Better?
When it comes to choosing which transformer core design is better, it highly depends on your needs and applications. For example, if you require a transformer for high-frequency current, then a core-type transformer would be the best option. However, if you're looking for a more compact transformer and easier to install, then a shell-type transformer would be a better choice.
When choosing between a core type or shell type transformer, it's important to consider the transformer's intended use and application. This will help you determine which type of transformer would be the best option for your needs.
At the end of the day, it's important to consult with a transformer expert to determine which type of transformer would best fit your specific application. At Daelim, we have a team of transformer experts who would be happy to help you choose the type of transformer for your needs. Contact us today to learn more.
Read more about losses: The Ultimate Guide To Losses In Transformer
Related Products
Related Article
14.4kV and 35kV Pad Mounted Transformer, Honduras
We exported 300kva, 750kva, 1500kva and 2500kva radial and loop feed transformers to Honduras this year. There were totally 24 units and we will update the pictures after installation.
Selecting the Finest Transformer Producers Worldwide
Transformer companies are responsible for ensuring that your large electrical appliances and infrastructure continue to function as generally intended. In this post, I'll go over everything you need to know to track down a trustworthy transformer producer across the globe.
Cryptocurrency Mining Power Transformer Solution
DAELIM Brand substation transformer is running in Venezuela