Amorphous Core Transformers: How They Reduce No-Load Losses by 70%
No-load loss is the electricity a transformer consumes 24/7, even when it's not carrying any load. It's the cost you pay just for having the transformer energized. For distribution transformers, this loss can account for a significant portion of total losses over the unit's life.
What causes no-load loss
No-load loss is mainly hysteresis loss and eddy current loss in the core. When the core is magnetized and demagnetized every cycle, the magnetic domains resist and generate heat. Eddy currents circulate within the core laminations and also generate heat. Better core material means lower loss.
CRGO vs Amorphous: the material difference
Conventional transformer cores use cold-rolled grain-oriented (CRGO) electrical steel. The grains are oriented in the rolling direction to improve magnetic properties, but the material still has a crystalline structure that resists magnetization.
Amorphous metal is different. It's made by rapidly cooling molten alloy at about one million degrees per second, so the atoms don't have time to form a crystal structure. The result is a non-crystalline, or amorphous, atomic arrangement. Because there are no grain boundaries, magnetization is much easier - and losses drop sharply.
Table 1: Core Material Comparison
| Item | CRGO Electrical Steel | Amorphous Metal Core |
| No-load loss | Baseline | 30–40% of CRGO (60–70% lower) |
| Core structure | Crystalline, grain-oriented | Non-crystalline, amorphous |
| Thickness | 0.18–0.35 mm | 0.02–0.03 mm |
| Upfront cost | Medium | Higher |
| Mechanical strength | Robust, tolerates vibration | Sensitive to mechanical stress |
| Best application | Large power transformers, heavy-load stations | Distribution transformers, high-tariff regions |
How the 70% reduction is achieved
The loss reduction comes from three things:
1.No grain boundaries. In CRGO, magnetic domains have to overcome grain boundaries to align. In amorphous metal, there are no grains, so alignment is easier.
2.Extremely thin ribbon. Amorphous ribbon is 0.02–0.03 mm thick, compared to 0.18–0.35 mm for CRGO. Thinner material means lower eddy current loss.
3.Higher resistivity. Amorphous alloy has higher electrical resistivity than CRGO, which further suppresses eddy currents.
Table 2: Loss Comparison at Different Capacity Levels
| Transformer Capacity | CRGO No-load Loss (W) | Amorphous No-load Loss (W) | Reduction |
| 100 kVA | 200 | 60 | 70% |
| 315 kVA | 480 | 144 | 70% |
| 630 kVA | 810 | 243 | 70% |
| 1000 kVA | 1150 | 345 | 70% |
| 2000 kVA | 2000 | 600 | 70% |
Note: Values are typical, actual values vary by design and standard.
Table 3: 10-Year Energy Saving Comparison (1000 kVA, 0.10 USD/kWh)
| Item | CRGO Transformer | Amorphous Transformer |
| No-load loss | 1150 W | 345 W |
| Annual no-load energy | 10,074 kWh | 3,022 kWh |
| Annual no-load cost | $1,007 | $302 |
| 10-year no-load cost | $10,070 | $3,020 |
| 10-year saving | - | $7,050 |
| Price premium | - | ~$2,000–3,000 |
| Payback period | - | ~3–4 years |
When amorphous makes sense
Amorphous core transformers cost more upfront. The premium is typically 10–20% higher than a comparable CRGO unit. Whether it's worth it depends on:
1.Electricity price. The higher the tariff, the faster the payback.
2.Load profile. If the transformer runs at low load most of the time, no-load loss dominates, and amorphous wins.
3.Duty cycle. For 24/7 distribution duty, amorphous is usually the better choice. For large power transformers that run near full load, CRGO with optimized design may still be more cost-effective.
Table 4: Total Owning Cost Comparison - 1000 kVA, 10 Years
| Item | CRGO Transformer | Amorphous Transformer |
| Purchase price | $18,000 | $20,500 |
| 10-year no-load loss cost | $10,070 | $3,020 |
| 10-year load loss cost | $12,000 | $12,000 |
| Maintenance (10 years) | $3,000 | $2,500 |
| Total 10-year cost | $43,070 | $38,020 |
| Difference | - | $5,050 cheaper |
Note: Illustrative figures for comparison.
Manufacturing challenges
Amorphous cores are not easy to work with. The ribbon is very thin and brittle. It can't be cut or stacked like CRGO laminations. Core construction involves winding the ribbon into a rectangular shape, then annealing and impregnating it. Handling damage is a real risk - a small crack can increase losses.
This is why not every factory makes amorphous transformers. It takes specialized equipment, trained operators, and strict process control.
What this means for buyers
If you're buying distribution transformers for a project with high electricity costs or continuous duty, amorphous cores deserve a close look. The premium pays back in a few years, and the savings continue for the remaining 20–25 years of the transformer's life.
Ask your supplier for the actual no-load loss value, not just the efficiency class. And check that the core isn't damaged during transport.
If you're comparing amorphous vs CRGO for your project, send us your load profile and electricity tariff. We'll help you run the numbers.
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References
1.IEC 60076-20:2017, Power transformers – Part 20: Energy efficiency of power transformers and reactors. International Electrotechnical Commission.
2.IEEE Std C57.12.01-2021, IEEE Standard for General Requirements for Dry-Type Distribution and Power Transformers. Institute of Electrical and Electronics Engineers.
3.U.S. Department of Energy. (2024). Energy Conservation Standards for Distribution Transformers, Final Rule.
4.EU Commission Regulation (EU) 2019/1781, Ecodesign requirements for power transformers.
5.GB/T 25446-2010, Amorphous alloy dry-type power transformers. Standardization Administration of China.
6.Hitachi Energy. Amorphous Metal Core Transformers: Technology and Lifecycle Cost Analysis. Technical Report.
7.ABB Transformer Handbook, 4th Edition. Chapter: Core materials and loss calculation.
8.CIGRÉ Working Group A2.21, Dry-Type Transformers: Design, Application and Service Experience, CIGRÉ Technical Brochure 447, 2010.