Transformer Cores and Coils: A Comprehensive Guide

Transformer cores and coils are at the center of how electricity gets to where it’s needed, even if we don’t typically think about them. As a transformer product manager at Giga Energy, I’ve seen how the smallest details about these two elements can affect the way transformers function as a whole. From their individual design to how they work together, everything about transformer cores and coils is clearly reflected not only in what transformers can do but also in what they can handle and even how much they will cost.

In this article, I’ll share what I’ve learned about cores and coils, including the challenges of designing them to keep up with the growing demand for electricity and the push for renewable energy. 

Why are Transformer Cores and Coils so Important?

Transformer cores and coils are crucial parts of transformers because they are responsible for changing voltage levels to ensure electricity gets transferred efficiently and reliably. The design of the core and coils can minimize energy losses, such as heat, which can otherwise reduce the overall performance and lifespan of a transformer. For example, disc coils are good at handling heat, while layer coils offer better mechanical strength. The shape and structure of the core also affect how well current flows through it. 

The same goes for core and coil materials: whichever you choose affects how efficiently the transformer works and can even impact how much it costs to run. Common core materials like silicon steel and amorphous metals are often used because they have great magnetic properties. Silicon steel is strong and helps the core carry more magnetic energy without losing much, while amorphous metals are designed to cut down on energy losses. The two most common coil materials are aluminum and copper. While aluminum is more cost affective, it is less conductive than copper entailing more material to handle the same current, so while aluminum windings are cheaper, they take up more space. Copper, while more expensive than aluminum, is more conductive which means higher efficiency and smaller footprints.  

Lastly, different core and coil designs will also affect overall transformer costs. While materials that are more advanced or specially designed may cost more upfront, they can save money in the long run by cutting down on energy loss and the need for repairs. 

What are Transformer Cores?

Transformer cores are the part of the transformer that help guide magnetic fields from one coil to another, allowing electricity to be transferred efficiently. Without the core, much of the energy would be wasted making the transformer less efficient and more expensive to operate.

Early transformer cores were made from basic iron, which wasn’t very efficient. As electricity usage grew, engineers started using better materials like silicon steel. These improvements allowed transformers to transfer energy more efficiently, helping cities get reliable power. 

Today’s transformer cores are made from materials like silicon and amorphous steel. These materials reduce energy loss and make transformers more efficient. As the world shifts to renewable energy, transformer cores are continuously improving to meet growing energy needs while minimizing waste.

Materials Used in Transformer Cores

The materials used in transformer cores have a big impact on how well they work. Some materials are better at guiding magnetic fields and reducing energy loss than others. Let’s take a look at the most common materials used to make transformer cores and how they help improve performance.

Silicon Steel

Silicon steel is the most common material used for transformer cores. It is great at guiding magnetic fields with minimal energy loss. The steel’s silicon content makes it more efficient than regular steel, which is why it’s used in most high-performance transformers. Grain-oriented silicon steel is engineered to align its magnetic properties in specific directions. This alignment helps reduce energy loss, making it ideal for large transformers used in power grids.

Silicon steel has been a key factor in improving transformer efficiency, allowing for better electricity distribution with less waste.

Amorphous Metals

Amorphous metals, unlike traditional metals, have a random atomic structure. This helps them reduce energy loss during magnetization, making them highly efficient.

Amorphous metal cores are used in transformers that handle renewable energy, such as wind and solar power, because they help reduce energy loss and make these systems more efficient. They will likely become more popular in the near future in order for manufacturers to comply with the upcoming increase in the DOE’s efficiency standards in 2028.  

How Transformer Cores and Coils Work Together

Transformer cores and coils work together to transfer electrical energy. The core of a transformer creates a path for the magnetic field, and the coils carry the electrical current that creates that magnetic field. Together, they convert electricity from one voltage to another, which is vital for the safe distribution of power to homes, factories, and equipment. The core guides the magnetic field created by the primary coil, allowing energy to be efficiently transferred from the primary to the secondary coil. Without a properly designed core, energy would be wasted, making the transformer less effective.

Core Designs That Reduce Energy Loss

The design of transformer cores helps minimize energy loss. Two types of energy loss are particularly important: hysteresis loss and eddy current loss.

• Hysteresis loss happens when the magnetic material is magnetized and demagnetized, using energy each time. High-quality materials like grain-oriented silicon steel reduce this type of loss.
• Eddy current loss occurs when currents form inside the core material. These currents create heat and waste energy. Laminated cores help reduce eddy currents by breaking them up, improving overall efficiency.

Common Core Designs

There are a few common core design elements that help reduce energy loss:

• Shell cores: These cores encase the coils, providing strength and reducing magnetic leakage, which is helpful for high-power transformers.
• Toroidal cores: These cores have a donut shape and reduce energy loss and noise. They are often used in smaller, quieter transformers.
• Laminated cores: These cores are made of thin layers of metal stacked together. This design reduces eddy currents and improves efficiency.

Materials Used in Transformer Coils

The materials used for the coils in transformers are just as important as the materials used for the core. The two most common materials for coils are:

Copper

Copper is the best material for transformer coils because it has excellent conductivity (60% more conductive than aluminum), which means it lets electricity flow through it with minimal resistance. This helps reduce energy loss. It also means that less material is needed, which entails a smaller physical footprint. 

Aluminum

While copper is more efficient, aluminum is a cheaper and lighter option. It’s light weight, reliability, and low cost make it a great option for standard distribution transformers. How Transformer Coils Work

Transformer coils use electricity to create magnetic fields, which allow the transformer to increase or decrease voltage.

• Primary coil: The primary coil generates a magnetic field when current flows through it.
• Secondary coil: The secondary coil picks up the magnetic field and converts it into electrical voltage, either increasing or decreasing the voltage depending on the ratio of windings. If the secondary coil has fewer winding turns than the primary coil, it will lower the voltage (and correspondingly raise the current). This is how a step-down transformer works. If the secondary coil has more winding turns than the primary coil, it will increase the voltage (and correspondingly decrease the current). This is how a step-up transformer works.

For example, in a residential transformer, the primary coil takes the high voltage from the power grid, and the secondary coil steps it down to a safe level for homes.

Real-World Examples of Transformer Cores and Coils

Transformer cores and coils are used in a lot of different contexts, from powering homes to supporting industrial systems. Some real-life examples of this include: 

• Neighborhood transformers: These transformers use laminated cores and copper coils to step down the voltage from the grid to a safe level for homes.

Optimizing Transformer Performance

There are a lot of different ways to make transformers more efficient. Using the best materials, improving core designs, and managing heat are all ways to reduce energy loss and improve performance.

Reduced Core Losses

Using materials like silicon steel and amorphous metals reduces core losses, making transformers more efficient by guiding magnetic fields more accurately and with less energy waste.

Improved Cooling

Transformers generate heat, which will shorten the lifespan of the transformer. Cooling methods such as oil immersion or natural air circulation help keep temperatures under control and ensure the transformer runs smoothly. For sensitive applications such as data centers, advanced cooling measures such as forced air circulation may be used to enhance thermal dissipation. 

Better Manufacturing Techniques

Improved manufacturing techniques, like precision coil winding and octagonal-shaped cores, are helping make transformer components more efficient. This improves the overall performance of transformers, leading to less energy waste.

The Future of Transformer Cores

New materials and manufacturing methods continue to improve transformer efficiency. Some exciting new developments include:

• Nanocrystalline alloys: These materials are highly efficient and may help further reduce energy loss in transformer cores.
• Superconducting materials: In the future, superconducting materials could eliminate energy loss entirely, offering a new level of efficiency. However, these materials are highly cost prohibitive, so it’s unlikely we’ll see transformers made out of superconductors like silver anytime soon.

As transformer technology advances, it will become even more energy-efficient and environmentally friendly, helping meet the growing global demand for energy.

By using these new materials and methods, transformer cores will continue to improve in performance, which will also lead to better energy distribution and lower costs for consumers.

After leaving my electrician role behind and transitioning into the transformer industry, I've come to appreciate just how crucial cores and coils are to the efficiency and reliability of transformers. These components are at the heart of how transformers manage and transfer magnetic energy, making them essential for energy conversion in everything from small-scale applications to large infrastructure projects.

At Giga Energy, we're focused on optimizing these parts to meet your specific needs. If you’re looking to discuss how transformer cores and coils can improve your system’s performance, feel free to reach out.

‍Contact us today to talk about your upcoming energization dates & projects.