Understanding Types of Transformer Winding and Their Applications

Common Types of Transformer Winding

At DAELIM Transformer, we use different transformer windings for different functions and configurations. 

Windings are arranged to produce a magnetomotive force (MMF), which the core transfers to other windings to achieve different voltage levels. 

Broadly, transformers are classified into two main types based on their core structure and winding arrangement:

• Core type transformer
• Shell type transformer

In our core type transformer, you’ll see the winding wrapped around the core. In contrast, with a shell type transformer, the core itself encases the winding.

Our winding design considers factors like current rating, short-circuit capacity, temperature limits, impedance, surge voltage, and transport requirements.

How About Transformer Winding Type For a Core Type Transformer?

Helical Winding

Helical winding comes in four forms, single, double, disc-helical, and multi-layer. We use helical winding in our low-voltage, high-capacity transformers. 

It is made up of rectangular conductor strips wrapped in helix form, positioned radially in parallel layers. 

Each turn spans the full radial depth of the winding. We use the utmost 16 parallel strips to make a conductor. 

Generally, we use four types of helix winding in our power transformers:

• Single Helix Winding: We orient single helical windings in an axial direction, following an inclined, screw-like path. Each winding has a single layer of turns, offering a streamlined design suited for low-voltage applications.
• Double Helix Winding: Double helical winding minimizes eddy current loss by reducing the number of parallel conductors. The design enhances transformer efficiency and reduces overall energy loss.

• Disc Helical Winding: We arrange strips in parallel and side by side along the radial direction to fully cover the winding’s radial depth.

• Multi-layer Helical Winding: We utilize this type of winding in our high-voltage transformers with ratings of 110 kV and above. We use multiple cylindrical layers, concentrically wound and we connected them in series.

Cylindrical Winding

For our low-voltage transformer with a power rating of 600-700 kVA and a current of 10-600 A, we use cylindrical winding.

We apply cylindrical windings in their multi-layer form. Rectangular conductors are used in a two-layered type to secure the lead-out ends. 

The layers of the windings are separated by oil ducts, allowing for effective cooling as oil circulates throughout the winding structure.

Continuous Disc & Disc Winding

We mainly apply disc winding in our power transformers as it facilitates a reliable transformer design. For the winding, we use discs or flat coils arranged in either series or parallel. 

We create the coils from rectangular conductor strips, wound in a spiral pattern outward from the center in a radial direction. 

One or more strip conductors are wound in parallel along the flat side, lending strength and durability to this winding style. 

Each disc is spaced by sectors attached to vertical strips, while additional spacers create radial and axial ducts. 

This design allows oil to circulate directly around each turn, facilitating efficient cooling and maintaining optimal transformer performance.

The advantage you get from disc and continuous disc winding is greater mechanical axial strength and affordability.

Crossover Winding

On many occasions, we apply this type of winding in the high-voltage winding of our small transformers.

We separate the layers of winding 0.5 to 1 mm and ensure the voltage is maintained at 800 and 1000.

Normally, the crossover type of winding has more strength compared to the cylindrical type of winding. Also, don't forget that crossover wind has lower impulse strength than cylindrical.  

You will also incur more labor costs when using a transformer with a crossover type of winding.

Types of Transformer Winding For Shell Type Transformer

Sandwich Type Winding

In sandwich windings, primary and secondary windings are arranged in alternating layers, basically “sandwiching” them together. 

The design enables the windings to share the magnetic field, enhancing transformer efficiency and reducing energy loss.

We ensure equal ampere-turns in each winding to balance the magnetomotive forces in the sections.

More resource: Why does transformer require a balanced winding?

Increasing the degree of subdivision reduces the overall reactance, resulting in improved electrical performance.

Benefits of Shell Type Winding in Transformers

• Enhanced Insulation: The core's structure provides superior insulation for windings, increasing safety, especially in high-voltage applications. 
• Reduced Leakage Flux: The core surrounding the windings confines magnetic flux, minimizing leakage flux and promoting higher efficiency.  
• Improved Mechanical Strength: A robust core structure offers strong support, reducing the risk of damage from external forces or short circuits.  
• Compact Design: The core-enclosing structure results in a more compact transformer, ideal for space-limited installations.  
• Better Heat Dissipation: The core helps spread heat, enhance cooling, and prolong the transformer's lifespan.
•  Higher Efficiency for Low to Medium Power: Particularly efficient in low to medium power applications due to reduced energy losses.  
• Better Short-Circuit Withstand Capability: Even distribution of magnetic forces in the shell design increases resistance to short circuits, improving fault tolerance.

Conclusion

In a nutshell, various types of transformer windings serve specific operational needs by optimizing efficiency, cooling, and mechanical strength. 

In core-type transformers, helical and cylindrical windings are often used to handle varying currents and maintain effective cooling for low to medium-voltage applications, while disc windings support high-capacity transformers with added durability.

Shell-type transformers use sandwich windings, where primary and secondary windings are layered to reduce energy loss and improve insulation. 

The design limits magnetic flux to minimize leakage and provides a compact, sturdy structure ideal for high-stress environments, making these transformers more efficient and reliable.

When choosing a transformer manufacturer and supplier, choose DAELIM Transformer for our certified solutions. Our services are UL/CUL, and CE certified. 

FAQs

1. What are the main types of windings in power transformers?

The main types of windings in power transformers include helical, disc, and cylindrical windings, with each type offering specific benefits for voltage, current capacity, and cooling.

2. What is winding in transformer?

Winding in a transformer is the coiled conductor that creates magnetic fields. The fields help transfer electrical energy from one winding to another, allowing voltage transformation.

3. What is the purpose of layer winding in transformer?

Layer winding refers to coils stacked in multiple layers to manage higher voltage and increase insulation, allowing safe operation in transformers that handle high voltages.