Amorphous Alloy Transformer Core: Low-Loss Magnetic Material Guide
Oct 13, 2025
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Key Takeaways
- Amorphous alloy cores cut transformer no-load loss to roughly one-third to one-fifth of conventional grain-oriented silicon steel, because the amorphous structure removes crystal-anisotropy hysteresis.
- No-load loss typically accounts for 60–80% of total loss in lightly loaded distribution transformers, so a low-loss core directly cuts annual energy cost.
- Amorphous strip is thin and brittle: winding must avoid sharp bending, and annealing after forming is mandatory to restore magnetic properties.
- Where cost per kVA and inrush behaviour matter, compare amorphous vs. silicon-steel cores on life-cycle energy cost, not first price.
What Is an Amorphous Alloy Transformer Core?
An amorphous alloy transformer core is the magnetic circuit component of a transformer built from ultra-thin amorphous soft-magnetic alloy strip (typically Fe-based, about 0.025–0.030 mm thick). The alloy is produced by rapid solidification: molten metal is cooled so fast that the atoms do not form a crystal lattice, leaving a disordered "glassy" structure. Because there is no crystal orientation, the magnetic domain rotation resistance is very low, and the hysteresis loss drops far below that of grain-oriented silicon steel.
In distribution transformers, no-load loss dominates total loss when the unit is lightly loaded. Because no-load loss runs 24 hours a day, a core that cuts it by 60–80% can repay its extra material cost within a few years of operation. This is why amorphous-core transformers are the standard choice for energy-efficiency-driven distribution projects worldwide.
Core Features of Amorphous Transformer Cores
| Feature | Description |
|---|---|
| Ultra-low hysteresis loss | No crystal anisotropy; hysteresis loss about 1/3–1/5 of high-grade silicon steel |
| Saturation flux density | ~1.56 T (Fe-based amorphous); slightly below silicon steel but adequate for medium/low-voltage transformers |
| Corrosion resistance | Natural oxide surface film; usually no additional protective coating needed |
| Thickness | ~0.025–0.030 mm strip, giving very low eddy-current loss |
| Fragility | Brittle in the as-cast state; handling and winding must avoid impact and tight bending |
Structure and Processing Requirements
Mainstream wound-core construction
The standard structure is a wound core: amorphous strip is continuously wound into a toroidal or rectangular closed loop, which minimizes air gaps (each gap adds magnetizing current and loss). Laminated constructions are also used in some designs, but lamination spacing must be tightly controlled to avoid stray-loss increase.
Processing key points
Amorphous strip is thin and brittle. Severe impact or bending during slitting, winding and handling must be avoided. After winding or laminating, the core requires a controlled annealing cycle to relieve internal stress; this restores low coercivity and high permeability and stabilizes the magnetic properties for service.
Applications
- Energy-efficient distribution transformers: replacing silicon-steel cores cuts no-load loss by hundreds to thousands of kWh per unit per year, meeting modern energy-efficiency regulations.
- Renewable energy: step-up transformers for PV and wind plants, and isolation transformers for battery energy storage systems, where low no-load loss improves plant economics.
- Special duty transformers: data-centre transformers and medical isolation transformers that run at low or no load for long periods, where low idle loss reduces long-term operating cost.
Amorphous vs. Silicon Steel Cores: What to Compare
| Item | Amorphous Core | Silicon Steel Core |
|---|---|---|
| No-load loss | Very low (key energy saving) | Higher |
| Load loss | Close to high-grade silicon steel | Mature, stable control |
| Cost | Higher material and process cost | Lower, widely available |
| Saturation & inrush | Lower Bs; higher inrush ratio; larger core volume | Higher Bs; smaller volume |
| Best fit | Lightly loaded distribution, renewables, special duty | General distribution, heavy load factor |
Amorphous ring Core specification
| Magnetic core size(mm) | Protective box size(mm) | Effective cross-sectional area Ae(mm2) | Magnetic path length Ie(mm) | Maximum DC overcurrent class (A) |
||||||
| id | od | ht | ID | OD | HT | |||||
| 14 | 19 | 6.5 | 12 | 22 | 8 | 11.86 | 51.81 | 20 | ||
| 14 | 20 | 10 | 12 | 22.3 | 11.4 | 29.68 | 52.29 | 40 | ||
| 16 | 21 | 10 | 15 | 24 | 12.3 | 24.85 | 57.41 | 60 | ||
| 16 | 23 | 8 | 15 | 24 | 9.7 | 20.44 | 61.23 | 60 | ||
| 16 | 23 | 10 | 15 | 24 | 12.3 | 34.62 | 59.92 | 60 | ||
| 17 | 22 | 10 | 15.3 | 24.4 | 12.3 | 24.86 | 60.59 | 60 | ||
| 17 | 21 | 8 | 15.3 | 24 | 9.7 | 25.56 | 60.67 | 60 | ||
| 17 | 23 | 8 | 15.3 | 24.4 | 9.7 | 26.89 | 61.34 | 60 | ||
| 18 | 23 | 10 | 16.4 | 24.4 | 12.3 | 29.78 | 60.38 | 70 | ||
| 18 | 24 | 9 | 16.4 | 25 | 11.2 | 34.78 | 60.89 | 70 | ||
| 18 | 25 | 10 | 16.4 | 25.9 | 12.3 | 37.97 | 64.56 | 70 | ||
| 19 | 24 | 9 | 17.3 | 25 | 11.2 | 40.39 | 65.32 | 80 | ||
| 19 | 25 | 10 | 17.3 | 26 | 12.3 | 39.42 | 62.31 | 80 | ||
| 19 | 26 | 10 | 17.3 | 27.3 | 12.3 | 48.32 | 69.56 | 80 | ||
| 20 | 25 | 10 | 18.5 | 26.3 | 12.3 | 39.29 | 70.32 | 90 | ||
| 20 | 28 | 10 | 18.5 | 29 | 12.3 | 45.76 | 73.88 | 90 | ||
| 20 | 32 | 10 | 18.5 | 32.3 | 12.3 | 58.91 | 78.75 | 90 | ||
| 21 | 29 | 10 | 18.2 | 31.3 | 12.3 | 39.65 | 77.19 | 100 | ||
| 21 | 26 | 8 | 18.3 | 27.4 | 9.7 | 46.54 | 78.32 | 100 | ||
| 21 | 28 | 10 | 18.3 | 30 | 12.3 | 50.39 | 77.45 | 100 | ||
| 22 | 28 | 10 | 20.5 | 30 | 12.3 | 49.32 | 79.89 | 120 | ||
| 22 | 32 | 10 | 20.5 | 33.4 | 12.3 | 43.58 | 73.43 | 120 | ||
| 23 | 32 | 10 | 21.3 | 33.4 | 12.3 | 44.56 | 74.56 | 120 | ||
FAQ
Q: How much lower is the no-load loss of an amorphous core compared with silicon steel?
A: Amorphous alloy cores typically reduce transformer no-load loss to about one-third to one-fifth of conventional grain-oriented silicon steel cores, because the amorphous structure has no crystal anisotropy and therefore lower hysteresis loss.
Q: Why is annealing necessary after winding an amorphous core?
A: Winding introduces internal stress into the brittle amorphous strip, which degrades magnetic properties. A controlled annealing cycle relieves this stress and restores low coercivity and high permeability.
Q: Do amorphous cores require special tank or oil design?
A: Not necessarily; the tank and oil system follow the same IEC 60076 rules as conventional transformers. The main design differences are core clamping (to avoid stress on the brittle strip) and core volume.
Send your transformer rating, voltage class and loss target. Our engineers will propose the core material and configuration, and supply measured no-load/load loss data per IEC 60076.
Email: sales@gneesteels.com｜ WhatsApp: +86-15824687445
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