How To Choose Silicon Steel Core Thickness

Classification of Silicon Steel (Electrical Steel) by Full Thickness Specifications
Silicon steel is divided into two major categories: cold-rolled grain-oriented silicon steel (CRGO) (the mainstream choice for transformer and current transformer cores) and cold-rolled non-grain-oriented silicon steel (NO) (for motors and EI-shaped laminated cores). The following table summarizes the full range of thicknesses and application-specific selection criteria based on common use cases.
I. Cold-Rolled Grain-Oriented Silicon Steel (CRGO) (Toroidal Transformers, Instrument Transformers)

1. Ultra-Thin High-Frequency Specifications (High-Frequency Power Supplies, High-Frequency Instrument Transformers)
   0.05 mm, 0.08 mm, 0.10 mm
   Features: Extremely low high-frequency eddy current losses; suitable for medium- and high-frequency inverter cores operating at 200 Hz and above; relatively high cost
2. Mainstream Mass-Production Specifications for Power Frequency (Standard for 50 Hz power frequency large toroidal cores; used in 90% of toroidal cores on the market)
   0.23 mm (Grades 23Q90, 23ZH85): High-end model with ultra-low losses; the top choice for energy-saving power distribution transformers and precision current transformers
   0.27 mm (Grades 27Q110, 27ZH105): Best-value option, widely used in high-power toroidal power transformers
   0.30 mm (Grades 30Q120, 30ZH120): Standard general-purpose grade, most commonly used in industrial power supplies and standard isolation transformers
   0.35 mm (Grade 35Q135): Lowest-cost grain-oriented silicon steel, used in high-power low-voltage distribution transformers and reactors
   II. Cold-Rolled Non-Grain-Oriented Silicon Steel (NO) (Motors, EI-type laminated cores, small power-frequency power supplies)
   Ultra-thin medium-frequency grades (new energy motors, high-frequency inductors)
   0.15 mm, 0.20 mm, 0.25 mm
   Standard Thicknesses for Mass Production
   0.35 mm: Inverter motors, small reactors, high-frequency switching power supply cores
   0.50 mm (most common): Household motors, EI transformers, ballasts, standard for small power-frequency power supplies
   0.65 mm: General-purpose small motors, low-end small silicon steel stamped parts
   III. Thickness Selection Logic
   50 Hz Power-Frequency High-Power Large-Ring Cores
   Preferred: 0.23 / 0.27 / 0.30 mm; choose 0.23 for energy efficiency, 0.27 for standard mass production, and 0.30 for cost control
   High-frequency inverters, photovoltaic systems, and charging station inductor cores
   Select thinner gauges: 0.08–0.20 mm to suppress high-frequency eddy current heating
   Large-volume power distribution transformer cores
   Commonly used: 0.30 mm and 0.35 mm grain-oriented silicon steel
   IV. Additional Tips
   The thinner the silicon steel, the lower the eddy current losses and the better the high-frequency performance; however, the unit price of the material is higher, and winding and processing are more difficult. For high-power applications at power frequency, there is no need to blindly use ultra-thin materials; 0.27/0.30 mm represents the industry’s optimal balance.