The transformer core (also known as the magnetic core) is the central magnetic circuit component of a transformer. Its material selection directly affects the transformer's efficiency, losses, and applicable scenarios. Based on operating frequency, power requirements, and cost factors, core materials can be categorized into the following types:   1. Traditional Silicon Steel Sheets (Fe-Si Alloy):​​ Composition: Cold-rolled steel sheets with silicon content ranging from 0.8% to 4.8% , typically with a thickness of  0.35mm or thinner​. Characteristics: High saturation magnetic induction (Bs≈1.6–1.7T), suitable for high-power scenarios at power frequencies (50/60 Hz). Laminated stacking: Insulating coatings are applied between layers to reduce eddy current losses. However, losses increase significantly at high frequencies​. Applications: Primarily used in power transformers and motor cores for low-frequency, high-power electrical equipment.   2. Ferrite Core​ Composition: Manganese-zinc (MnZn) or nickel-zinc (NiZn) ferrite, classified as sintered magnetic metal oxides. Characteristics: High resistivity: Significantly reduces eddy current losses at high frequencies, suitable for a ​frequency range of 1 kHz——1 MHz​ . Low saturation flux density (Bs ≈<0.5T), weak DC bias capability, and prone to magnetic saturation. Applications: Widely used in electronic devices such as switch-mode power supplies (SMPS)​, ​high-frequency transformers, and inductors.   3. Metal Magnetic Powder Cores Types: Iron powder cores Iron-silicon-aluminum powder cores (FeSiAl) High-flux powder cores (HighFlux) Molybdenum permalloy powder cores (MPP) . Characteristics: Strong anti-saturation capability: Reduces eddy currents through insulation-coated dispersed magnetic particles, making it suitable for DC superposition scenarios . Medium permeability (μe≈10—125) with a frequency range of 10 kHz - 100 kHz​ . Applications: Widely used in medium-to-high-frequency power devices such as: ​PFC inductors (Power Factor Correction) ​Filter inductors.   4. Novel Alloy Materials​ Amorphous Alloys​ Composition: Iron-based (e.g., Fe₈₀B₁₀Si₁₀) or cobalt-based amorphous ribbons, characterized by disordered atomic arrangement​ . ​Advantages: ​Ultra-low core losses (only 1/5 of silicon steel), enabling significant energy savings . Limitation: Significant magnetostriction (resulting in higher operating noise) . ​Applications: Energy-efficient distribution transformers.   Nanocrystalline Alloys​ ​Structure: ​Nano-scale crystalline grains (<50 nm) embedded in an amorphous matrix . ​Advantages: ​High permeability & low losses (superior to ferrites at 50 kHz) . ​Strong harmonic resistance and excellent thermal stability (operating range: -40–120°C) . ​Applications: ​High-frequency transformers and PV inverters​ . ​EV electric drive systems (e.g., integrated OBC/DC-DC modules）   Key Factors in Material Selection​ ​Operating Frequency​ ​Low Frequency (≤1 kHz) : ​Silicon Steel or Amorphous Alloys (e.g., Fe₈₀B₁₀Si₁₀). High Frequency (>10 kHz) : ​Ferrite Cores (MnZn/NiZn) or Nanocrystalline Alloys.   Loss Requirements​ ​Lowest Core Loss: ​Amorphous/Nanocrystalline Alloys. High-Frequency Loss Optimization: ​Ferrites.   Cost and Process ​Cost-Effectiveness & Maturity: ​Silicon Steel. High Initial Cost with Long-Term ROI: ​Amorphous/Nanocrystalline Alloys.​  

The motor lamination's punch size is given by the design. The following discusses the factors that affect quality in manufacturing when the design remains unchanged. 1. Loss and magnetic permeability of silicon steel sheets The specific loss properties of silicon steel sheets from different manufacturers and different batch numbers from the same manufacturer are not exactly the same. Although there are standard prescribed values, they fluctuate within a certain range. If the amplitude of the fluctuation is relatively large, or the material of the silicon steel sheet itself does not meet the requirements, then the use of such silicon steel sheets on the motor will greatly affect the performance of the motor, especially for medium and large motors, where iron loss accounts for 10% of the loss. The larger the proportion, the more obvious the impact on performance (mainly temperature rise and power factor). This is a hidden danger that is difficult to detect from the electromagnetic design. 2. Silicon steel sheet mold is out of tolerance Silicon steel sheet molds, such as slot punching dies and release molds, have a gap between the punch and the die that gradually increases during use. Some manufacturers are still dealing with production when the mold is out of tolerance, and the consequences are: the punching burrs are significantly increased. If the burr is large, the iron loss and no-load current will increase, causing the temperature rise of the motor to increase, the power factor to decrease, and the efficiency to decrease. 3. Insulation between silicon steel sheets The insulation between silicon steel sheets can suppress the eddy current in the iron core, thereby reducing the resulting eddy current loss (it is included in the iron loss). The insulating layer between chips is formed in the following three ways: (1) Inter-chip insulation composed of the paint film of the cold-rolled silicon steel sheets; (2) The motor manufacturer applies insulating paint on the punched sheets without paint film; (3) The motor manufacturer oxidizes the punched sheets to form an insulating layer .