Class: 3D Wound Core
The 3D wound core is wound by either silicon steel or amorphous alloy strip to form three identical rectangular core frames of which core leg cross section is nearly semi-circular. After joining the frames together, the top-view is of equilateral triangle.
1. Curve Slitting
A curve core material strip cut by self-developed slitting machine can result in high sectional filling factor up to 97.5~98.5%.
Result: Smaller diameter, less core and winding material consumption due to higher filling factor
2. Core Winding
Make three identical core frames of good integrity with special core winding machine. And join them together to have equilateral triangle core, viewed from the top.
（1）No horizontal air gap perpendicular to magnetic circuit.
（2）The flow direction of the flux is the same as that of the high conductivity direction (1,0,0) of silicon steel.
Result: Greatly reduced no-load loss, no-load current and sound level
3. Core Annealing
Four corners of a core frame will be deformed during core winding process, resulting in a great stress and more than 60% additional loss. They can be eliminated by core annealing.
Result: Totally recover silicon steel magnetic performance
Comparison with EI Core
1. Low Loss: More Energy-saving
Comparing with EI core transformer, the average no-load current of 3D wound core oil immersed transformer is reduced by 80%; and the average no-load current of 3D wound core oil immersed transformer is reduced by 60%.
2. Strong Ability to Withstand Short-circuit, Even Temperature Field: Safer
Cross-section of winding of 3D wound core transformer is circular, subjected to symmetrical force in three phases. Therefore, it has strong ability to withstand short-circuit.
Circuit, as well as even oil (air) duct, equilateral triangular arrangement of three-phase windings, low hot-spot temperature rise
3. Low Sound Level and Periphery Electromagnetic Field Strength: More Environmental-friendly
Low Sound Level: In comparison with EI core, its sound level can be reduced by 10dB-25dB, which is nearly muted.
Low Periphery Electromagnetic Field Strength: Greatly reduced electromagnetic stray field around the transformer, its magnetic flux leakage is only half of EI core's.