How to optimize the core design of current transformers?
Sep 03, 2025| I. Material Optimization
1. Application of High-Permeability Materials
Using nanocrystalline alloys (1J85) or high-grade silicon steel (such as 30ZH120), magnetic permeabilities can reach 10⁴-10⁵, reducing excitation current errors.
Core Loss Control: Core loss after lamination of high-quality silicon steel sheets is ≤1.2W/kg (50Hz/1.5T).
2. Anti-Saturation Design
Avoid adding steel to the core (which reduces effective permeability). Air gap design (gap length 0.1-0.3mm) is preferred.
Multi-core series construction disperses magnetic flux density and improves DC component immunity.
II. Structural Improvement
1. Lamination Process Optimization
Silicon steel sheets are stacked at a 45° angle along the magnetic flux lines, reducing eddy current losses by over 40%. Lamination thickness is controlled between 0.23-0.35mm, with interlayer insulation resistance ≥ 10⁶Ω·cm
2. Magnetic Circuit Symmetry
Using a toroidal core or C-shaped symmetrical structure reduces leakage flux by 30%-50%.
Evenly distribute the windings to avoid localized excessive flux density (recommended flux density ≤1.2T).
III. Process Control
1. Annealing
Vacuum annealing (750-850°C) eliminates internal stress and increases permeability by 15%-20%.
2. Compensation Technology
Turns Compensation: Increase the secondary winding's turns by 0.1%-0.5% to control the ratio error within ±0.1%.
Magnetic Shunt Compensation: Shunts are provided in the non-operating area of the core to reduce angular error to within 5°C.
IV. Standard Compliance
The design must meet the accuracy class (e.g., Class 0.2S) and temperature rise limit (≤65K) requirements of GB1208-2006.
IEC 60046-1 for high-frequency applications requires verification. Frequency response characteristics of 60044-1 (0.1Hz-10kHz)
