1. During the material formation process, amorphous alloys are subjected to rapid cooling and stress generation during core winding. Amorphous alloy core materials are highly sensitive to mechanical stress, including tensile and bending stresses, which can adversely affect their magnetic properties. To achieve optimal loss characteristics, amorphous alloy cores must undergo annealing under specific magnetic field conditions after forming. The annealing process is complex and requires stringent controls.
2. Since the loss of amorphous alloy cores increases with pressure, structural design considerations must include suitable and effective measures to manage stress during annealing.
3. After annealing, amorphous alloy core materials become brittle and prone to chipping. This necessitates special process measures during production.
4. Amorphous alloy core sheets are extremely thin, with a thickness of only 0.025 mm—less than one-tenth that of commonly used silicon steel sheets. Additionally, the stacking factor of amorphous alloy cores is relatively low, at approximately 0.86.
5. The saturation magnetic flux density of amorphous alloys is relatively low (about 1.5 T), resulting in a lower rated magnetic flux density (1.3–1.4 T) compared to cold-rolled silicon steel sheets (1.6–1.7 T). This imposes certain limitations on product design.
6. Structural Forms of Amorphous Alloy Cores:
Single-phase amorphous alloy core transformers typically use a "frame" structure.
Three-phase amorphous alloy core transformers consist of four frames combined into a five-column structure.
An eight-frame stacked structure is commonly adopted for transformers with capacities of 500 kVA or higher.
Performance of Amorphous Alloy Transformers
No-Load Loss
The iron-based amorphous alloy material used in cores lacks a crystalline structure, resulting in low magnetization power and high electrical resistivity, thereby minimizing eddy current losses. Consequently, the no-load loss and no-load current of amorphous alloy transformers are significantly low—approximately 35% of the no-load loss of S11-type distribution transformers. This makes them ideal for rural areas, towns, schools, and street lighting with fluctuating power demands.
Concerns about increased no-load loss during operation are unnecessary, as the Curie temperature (415°C) and crystallization temperature (550°C) of amorphous alloys are sufficiently high to ensure stability during manufacturing, annealing, normal operation, and short-circuit thermal conditions.
Winding Connection Group
For three-phase transformers, the four-frame, five-column structure ensures independent magnetic circuits for each phase. Magnetic flux in each frame comprises fundamental wave flux and third harmonic flux, with the third harmonic flux canceling out due to opposing phase alignment within a single winding. Consequently, there is no third harmonic voltage component in the induced secondary voltage.
The high-voltage winding typically adopts a delta (D) connection, beneficial for eliminating single-phase ground faults and optimizing transformer capacity utilization. The connection group is usually D,yn11.
Short-Circuit Resistance
High and low-voltage windings are specially wound and supported on independent structures, secured with laminated wood to minimize stress on the core. This reduces radial deformation of coils during sudden short circuits, enhancing the transformer's ability to withstand mechanical stress and ensuring excellent short-circuit resistance.
Noise Levels
Noise in transformers arises mainly from the magnetostrictive properties of core materials, which are influenced by core size and magnetic flux density. Although amorphous alloys exhibit higher magnetostriction at the same flux density compared to cold-rolled silicon steel sheets, their lower saturation flux density (approximately 1.5 T vs. 2.03 T) results in similar actual magnetostriction levels under rated conditions. Proper design and manufacturing techniques can ensure noise levels comparable to silicon steel core transformers despite the larger mass and effective cross-sectional area (40% greater) of amorphous alloy cores.
Economic and Environmental Benefits
Amorphous alloy transformers offer significant energy-saving potential due to their low no-load loss, reducing transformer-related grid losses. Economic analysis comparing SH15-type amorphous alloy distribution transformers with S9-type conventional transformers shows that the initial investment difference is recovered through energy savings within three years, followed by long-term benefits for users.
Nationwide adoption of amorphous alloy transformers in China, where annual transformer demand is approximately 100 million kVA, could save over 20 billion kWh of electricity and reduce annual energy costs by nearly 10 billion RMB. Additionally, this would result in substantial environmental benefits, including reduced CO₂ and SO₂ emissions and minimized non-recyclable waste. From a long-term perspective, promoting amorphous alloy transformers significantly contributes to energy conservation and environmental protection, making it a highly recommended technology.