Many people assume that increasing the silicon percentage in transformer steel automatically leads to better transformer performance. In reality, the situation is far more nuanced. The silicon content alone is not the decisive factor. Instead, what shapes the performance of a transformer core is:

• Whether the material is grain oriented silicon steel (GO steel) or non-oriented electrical steel, and

• How well the material is processed during core fabrication.

Even if two cores use the same grade of transformer steel, their final performance can differ dramatically when heat treatment or winding techniques vary. In some cases, improperly processed cores may require five times the magnetizing current to reach the same magnetic flux density as a properly treated one.
Key indicators such as magnetizing current, core loss, and saturation characteristics remain the most reliable ways to judge transformer core quality.

Do Spliced Silicon Steel Strips Always Reduce Toroidal Transformer Quality?

Not necessarily. It’s true that each splice in a toroidal core—usually wound from CRGO steel—creates a potential leakage point. For this reason, keeping the number of joints below two or three is ideal.

All splice positions should also be chemically cleaned before assembly to ensure stable magnetic performance.
However, when it comes to high-end audio transformers or Hi-Fi applications, manufacturers generally prefer unspliced silicon steel transformer cores to guarantee minimal leakage and the highest consistency.

Understanding the Silicon Steel Materials Used in Transformer Cores

Silicon steel is chosen for transformer steel applications because it exhibits low loss under alternating magnetic fields. The main categories include:

1. Hot-Rolled Electrical Steel

Used mostly in general EI transformers. Grades such as D41, D42, D43, and D301 are common.

2. Cold-Rolled Electrical Steel (CRGO / CRNGO)

Cold-rolled steel offers better magnetic permeability and lower core loss and includes:

• Grain Oriented Silicon Steel (CRGO steel) for power transformers, toroidal cores, and C-cores

• Non-Grain Oriented Steel for motors and rotating machines

For EI transformers, steel sheets are punched into 0.35–0.5 mm laminations, heat treated, and installed. Toroidal and C-core transformers, by contrast, are typically wound from cold-rolled grain oriented silicon steel, followed by additional heat treatment and coating.

Why Does Leakage Inductance Occur in Transformers?

Leakage inductance comes from magnetic flux that doesn’t pass through both primary and secondary coils. These stray flux lines travel through the air along their own magnetic paths.
To reduce leakage inductance, manufacturers increase the coupling between the two windings.

Industry guidelines suggest that:

• A normal high-quality transformer should have leakage inductance less than 1/100 of the primary inductance,

• Hi-Fi tube amplifier output transformers should meet a stricter requirement of less than 1/500.

Looking for Reliable Transformer Core Steel?

Choose MOOPEC for Professional Support

If you need high-performance grain oriented silicon steel, CRGO transformer steel, or precision-processed transformer core materials, MOOPEC provides dependable and flexible supply solutions:

• High-permeability GO steel with stable magnetic properties

• Custom slitting, small-batch supply, and quick sampling

• Consistent quality for EI laminations, toroidal cores, and C-cores

• Technical guidance for transformer core design and material selection

👉 Enhance efficiency, reduce loss, and achieve stable transformer performance with MOOPEC’s transformer steel expertise