Comparison of no-load loss characteristics of amorphous alloy transformers and discussion on energy efficiency improvement

1. Background and significance of transformer energy saving

During the energy transmission process of the power system, the power loss generated by the transformer itself cannot be ignored. According to statistics, the total loss of distribution transformers accounts for about 30% of the entire power grid loss. The loss of the transformer is mainly divided into no-load loss (Iron Loss/No-load Loss) and load loss (Copper Loss/Load Loss).

Among them, the no-load loss is caused by the hysteresis loss and eddy current loss of the iron core material. As long as the transformer is charged, regardless of whether it is loaded or not, this part of the loss will continue to exist. Therefore, reducing no-load losses is the most effective means to achieve long-term, all-weather energy conservation of transformers. Amorphous alloy materials have natural physical advantages in reducing hysteresis loss due to their unique atomic arrangement structure.

2. Energy-saving mechanism of amorphous alloy transformer

Amorphous Alloy is a metallic glass material in which the atoms are arranged in long-range disorder and short-range order. It is prepared using ultra-quenching technology (cooling speed up to 10⁶ K/s). The molten metal is sprayed onto a high-speed rotating cooling roller and instantly solidifies into a thin strip with a thickness of only about 0.03 mm.

This special structure gives amorphous alloys three major physical advantages:

1. Extremely high resistivity: about 3 times that of oriented silicon steel sheets, significantly suppressing eddy current losses;

2. The hysteresis loop is extremely narrow: the coercive force is low, the magnetic permeability is high, and the energy loss during the magnetization process is small;

3. No grain boundaries: Eliminates the resistance to movement of magnetic domain walls of traditional crystal materials.

It is these microscopic characteristics that make the core loss of amorphous alloy only 20% to 30% of that of traditional oriented silicon steel sheets.

3. Comparative analysis of no-load loss characteristics

3.1 Comparison of loss values

Taking a typical 10 kV distribution transformer as an example (according to GB 20052-2020 "Energy Efficiency Limits and Energy Efficiency Levels of Power Transformers"):

It can be seen that the no-load loss advantage of amorphous alloy transformers becomes more and more obvious as the capacity increases.

3.2 Comparison of load characteristics

Conclusion: Amorphous alloy transformers are particularly suitable for scenarios with large load factor fluctuations, long-term light loads or low loads at night, such as residential areas, commercial buildings, new energy power stations, etc.

3.3 Life cycle cost (LCC) analysis

Although the initial purchase cost of amorphous alloy transformers is about 15% to 25% higher than that of S13 silicon steel transformers, based on its typical 20-year operation cycle:

• Annual operating time: 8760 h
• No-load loss difference: about 150 W
• Annual power saving: about 1300 kWh
• 20-year electricity saving income: calculated at 0.6 yuan/kWh, about 15,000 to 20,000 yuan

The investment payback period is generally 4 to 7 years, after which it enters the net income stage. The lower the load factor, the shorter the payback period.

4. Realistic bottlenecks in improving energy efficiency of amorphous alloy transformers

Although amorphous alloy transformers have obvious advantages, they still face the following challenges in the process of large-scale promotion and further tapping of potential:

1. Mechanical stress sensitivity (annealing brittleness):

Amorphous alloy strip is extremely thin and hard, making it very sensitive to mechanical stress. During the core lamination, shearing, coil winding, and assembly processes, once internal stress is generated, its disordered structure will be destroyed, resulting in a sharp increase in loss (possibly doubling). This is the biggest pain point in the manufacturing process.

2. Noise problem:

The magnetostriction coefficient of amorphous alloy is larger than that of silicon steel sheet. Under the action of alternating magnetic field, the iron core vibrates at a greater amplitude, resulting in the operating noise of the transformer usually being 5-10 dB(A) higher than that of a silicon steel sheet transformer of the same capacity.

3. Material cost and recycling system:

The price of amorphous alloy strips is much higher than that of silicon steel sheets, resulting in a higher initial purchase cost of transformers. In addition, the industrial chain for recycling and reusing scraps of amorphous alloys is not yet complete, which increases the life cycle cost.

4. Short circuit resistance:

Amorphous alloy iron cores cannot withstand huge electric power through high-strength binding like silicon steel sheets, and usually require special support structures to ensure mechanical stability during short circuits.

5. Discussion on paths to improve energy efficiency

5.1 Material level: developing a new generation of amorphous and composite strips

• High saturation magnetic density amorphous alloy: through composition optimization (such as adding Cu, Nb and other elements), the saturation magnetic density is increased to more than 1.5 T and the core volume is reduced;
• Nanocrystalline alloy application: Using Finemet-like nanocrystalline materials (such as FeCuNbSiB) to make the core, the loss can be reduced by 20% compared with conventional amorphous, and the noise and temperature rise characteristics are better, suitable for high-end scenarios;
• Amorphous/silicon steel composite core: Use amorphous strips in low-loss areas of the core and silicon steel sheets in high-magnetic-flux-density areas to achieve a compromise between performance and cost.

5.2 Design level: structural innovation and accurate simulation

• Three-dimensional magnetic circuit optimization design: Use electromagnetic simulation software such as ANSYS Maxwell and JMAG to perform parameterized optimization of the core joint structure and window height and window ratio to reduce local saturation and additional losses;
• Three-dimensional wound core structure: Compared with the flat laminated type, the wound core has no seams and continuous magnetic circuits. The no-load loss can be reduced by 10% to 15%, and the noise is significantly improved;
• Intelligent temperature control and cooling system design: optimize oil channel layout and heat sink configuration, control temperature rise, and indirectly reduce load loss.

5.3 Manufacturing process level: refinement and automation

• Core annealing process upgrade: Precision annealing in a protective atmosphere (precise control of temperature, time, and cooling rate) is used to eliminate internal stress and restore magnetic properties, which can reduce the loss by another 5% to 8%;
• Robot automatic cutting and stacking: reduce strip damage and assembly deviations caused by manual operations, and improve consistency;
• Low-loss lead structure and fuel tank shielding design: reduce stray losses and structural component heating.

5.4 Operation and maintenance level: digital empowerment

• Online loss monitoring system: equipped with intelligent sensors to collect voltage, current, and temperature data in real time, calculate real-time loss based on the big data platform, and detect abnormalities in time;
• Dynamic load matching and reactive power optimization: Combined with power load prediction, rationally arrange transformer switching and parallel operation strategies to ensure long-term operation within the economic range;
• Preventive maintenance: regular oil chromatography analysis and core ground current detection to prevent deterioration of losses caused by hidden defects.

5.5 Policy and standards level: improving energy efficiency ecology

• Promote the integration of energy efficiency standards with international standards (such as benchmarking IEEE C57, IEC 60076) and raise the entry threshold;
• Improve the energy-saving transformer subsidy mechanism and green procurement catalog to shorten the user investment payback period;
• Establish a carbon footprint accounting system for the entire life cycle of transformers, and include no-load losses into carbon emissions trading considerations.

6. Conclusion

Relying on the ultra-low hysteresis loss brought by its glassy physical structure, amorphous alloy transformers have irreplaceable strategic value in reducing no-load losses in distribution networks. Quantitative comparison shows that its no-load loss can be reduced by more than 60% compared with traditional silicon steel transformers, and is especially suitable for light-load, intermittent or long-term energized operation scenarios.

In the future, to further unleash the energy efficiency potential of amorphous alloy transformers, their sensitivity to mechanical stress and noise problems must be overcome. By promoting three-dimensional wound core technology, optimizing annealing processes, introducing nanocrystalline composite materials, and establishing a full life cycle cost management system, amorphous alloy transformers will play a more critical role in the construction of new power systems and provide solid hardware support to achieve the goal of "carbon peaking and carbon neutrality."