Did you know that 25-35% of energy losses in a transformer occur in the core itself? That’s a significant figure, especially when we rely on transformers to power everything from industrial machinery to everyday appliances. These losses not only impact performance but also lead to increased operational costs and thermal stress over time. Efficiency is everything when it comes to transformers and at the heart of an efficient transformer, lies its core. This core is meticulously engineered to optimize losses and the core material is a critical factor in this endeavor.
But what does that mean and why does it matter? This blog will tell you all about it.
What are laminations and why does the material used matter?
Transformer cores are made of laminations and rectangular cores are primarily made by stacking multiple thin layers of high-grade silicon steel. This multilayered structure is not uncalculated, it’s a deliberate design choice rooted in electromagnetic theory. By stacking sheets instead of using a solid core, there is a significant drop in energy loss due to eddy currents and improvement in the overall efficiency of the transformer.
The quality of this core material plays a crucial role in determining core performance. Higher-quality lamination material leads to lower core losses, improved magnetic permeability, and longer operational life. This is why the appropriate grade lamination material is especially vital in power transformers, distribution transformers, and high-frequency transformers used in critical infrastructure like power grids, renewable energy systems etc.
When it comes to transformer cores, not all materials are created equal. Silicon steel is the industry staple, available in two main types, Cold Rolled Grain Oriented (CRGO) and Cold Rolled Non-Oriented (CRNO). CRGO is the go-to choice for power and distribution transformers thanks to its grain structure, which channels magnetic flow more efficiently and reduces energy losses.
For designers chasing ultra-low core losses, amorphous alloys step in. They’re more expensive and a bit brittle, but their energy savings over time can be worth it. Taking things a step further, nanocrystalline cores offer exceptional magnetic performance, making them perfect for high-frequency and precision applications.
Not all transformers work at low frequencies though, in high-frequency devices like SMPS, ferrite cores shine. They’re lightweight, compact, and handle rapid magnetic switching with minimal eddy current losses, though they’re not suitable for high-power low-frequency work.
The right lamination material directly impacts efficiency, size, and frequency range, whether it’s powering an entire grid, a renewable energy system, or something as small as the charger in your hand. We’ll explore each of these materials in more detail as we continue through the blog.
Why are laminations important?
Laminations are crucial for minimizing eddy current losses. Eddy currents are unwanted, small loops of current induced in the transformer core due to changing magnetic fields. As a result of eddy currents, there is:
- Heat loss
- Lower efficiency
- Potential overheating
Without proper core design, the transformer is simply an energy-wasting heat machine.
Using laminations as the core material is the most effective way to cut down eddy current losses. Here’s how the transformer core lamination material helps:
- Using laminations to make a transformer’s core gives small gaps in between, which enhances the coil’s resistance. This resistance will decrease the total current and thus holds the eddy current losses.
- Laminations restrict the size of current loops, thereby reducing heat loss
- Overall, the transformer performs more efficiently
Usage of Silicon Steel
Statistics show that the transformer core market is a significant industry, valued at over $10 billion in 2024 and projected to grow. Within this market, silicon steel, particularly grain-oriented steel, remains the dominant material for manufacturing transformer cores. The cost of silicon steel can even account for a substantial part of a transformer’s total production cost, sometimes even ranging from 30% to 40%. It is important to note that silicon steel comes in two main forms which are differentiated by their grain structure. They are,
- CRGO (Cold-rolled Grain-oriented) Steel – this is the gold standard for power and distribution transformers. It has very low hysteresis loss (i.e. less energy wasted in each magnetic cycle) and high magnetic permeability (i.e. allows magnetic fields to pass through easily). This is primarily used in transformers where minimizing core loss is paramount.
- CRNO (Cold-rolled Non-grain-oriented) Steel – while not as efficient as CRGO, CRNO is more cost-effective and provides consistent magnetic performance in all directions making it suitable for applications where the magnetic flux changes direction, like in motors. The manufacturing process of CRNO is less complex than that of CRGO. There are also more producers of CRNO globally. This is typically available in thicker laminations in comparison to CRGO which serves as a reason for the higher core losses.
Beyond Silicon Steel: Other Transformer Core Lamination Materials
While silicon steel is used as much as it is, it’s not the only option available. Advancements in science have led to the development of other materials that offer unique advantages for specific applications. Here are some of the key materials used for transformer core lamination:
- Amorphous Alloys – Also known as metallic glass, these materials have a non-crystalline atomic structure which is different from the regular crystalline structure of silicon steel. This unique structure results in significantly lower hysteresis and eddy current losses, thereby making them highly energy-efficient. However, they are brittle and can be more difficult to work with than silicon steel.
- Nanocrystalline Cores – These are advanced iron-based alloys with a refined, nanoscale crystalline structure. They offer even better performance than amorphous alloys in high frequency applications exhibiting extremely low core losses and excellent magnetic properties.
- Ferrite Cores – These are ceramic compounds made from iron oxide and other metallic items. They are lightweight and offer very low losses at high frequencies. They are, however, more fragile and more expensive than silicon steel cores.
The table below shows a quick comparison of these key materials.
| Core Material | Key Advantage | Best suited for |
| CRGO Steel | Extremely low hysteresis loss, high permeability | Power and distribution transformers where efficiency is critical |
| CRNO Steel | Cost effective, consistent performance | Motors, generators and smaller transformers |
| Amorphous alloys | Significantly lower core losses than silicon steel | High frequency inductors and energy-efficient transformers |
| Nanocrystalline cores | Extremely low core losses at high frequencies | High frequency transformers and modern power electronics |
| Ferrite cores | Very low losses at very high frequencies. | High frequency RF transformers, SMPS, and EMI filters |
Conclusion
It’s not just about stacking metal sheets together, it’s about choosing the right material to build something reliable, long-lasting, and energy-efficient. By using the right lamination material, unnecessary energy loss due to eddy currents can be reduced and magnetic flow can be improved. That’s what smart engineering is all about: thoughtful design, purposeful choices, and performance that speaks for itself.
Ready to put this knowledge to work? Reach out to experts like us to ensure your projects are built to achieve the highest standards of performance and efficiency.