Grain-oriented silicon steel / Power transformers
Application · Power transformers
CRGO Steel for Power Transformers
Power transformer cores run for decades under near-continuous load, so no-load loss compounds into a real lifetime cost. We supply Hi-B and laser-scribed grain-oriented steel at 0.23–0.30mm, engineered for the lowest core loss and highest permeability in large power cores — built to meet the efficiency levels called for under IEC 60076-1, DOE 10 CFR Part 431, EU Ecodesign Tier 2 and China’s GB 20052.
Why no-load loss matters here
Loss you pay for every hour, for decades
A distribution transformer cycles with demand; a power transformer often runs near-continuously for 25–40 years. No-load (core) loss is present the entire time the unit is energised, regardless of load — so a small difference in W/kg compounds into a large lifetime energy cost.
This is why utilities and large industrial buyers rarely evaluate transformer bids on purchase price alone. Many specifications apply capitalized loss evaluation — assigning a dollar-per-watt penalty (commonly called “A” and “B” factors under IEEE C57.120 and similar utility practice) to no-load and load losses, then adding that penalty to the purchase price to get a true lifetime cost. Under this method, a transformer with a higher sticker price but lower core loss frequently wins the bid, because the core loss saving over 25+ years outweighs the price difference many times over.
Regulatory efficiency mandates reinforce the same logic. IEC 60076-1 defines the loss and efficiency framework most international specs reference; DOE 10 CFR Part 431 sets minimum efficiency levels for power transformers sold in the US; the EU’s Ecodesign Regulation (EU) 548/2014 Tier 2 does the same for the European market; and China’s GB 20052 sets minimum efficiency grades domestically. All four push core material selection toward Hi-B and laser-scribed CRGO, since Standard CRGO alone often can’t clear the newer efficiency thresholds on large units.
What we recommend
Efficiency standards that shape specs
Four frameworks buyers spec against
Whichever market you’re building for, one of these usually sets the efficiency floor your core steel needs to clear.
IEC
IEC 60076-1
The international baseline for transformer losses and efficiency, referenced by most non-US, non-EU specs worldwide.
US
DOE 10 CFR Part 431
US federal minimum efficiency levels for distribution and power transformers — Hi-B is common on units sized to clear it comfortably.
EU
Ecodesign (EU) 548/2014 Tier 2
The EU’s current efficiency tier for power transformers, tightened from Tier 1 — pushes core selection toward lower-loss grades.
CN
GB 20052
China’s minimum allowable energy efficiency standard for transformers, with grade tiers similar in spirit to DOE and Ecodesign.
Recommended grades
Grain-oriented lines for power cores
Power transformers most often specify Hi-B; Standard CRGO remains an option where cost outweighs the last fraction of loss.
Hi-B & Laser-Scribed
Domain-refined for the lowest loss and highest permeability — the default choice for large power cores.
- Thickness0.23 mm
- Core loss P1.7/50≤ 0.85 W/kg
- Induction B8≥ 1.92 T
Standard CRGO
Conventional grain-oriented grades for power cores where budget outweighs marginal loss gains.
- Thickness0.27–0.35 mm
- Core loss P1.7/50≤ 0.90 W/kg
- Induction B8≥ 1.88 T
Grain-Oriented Hub
Compare all three CRGO lines side by side before you commit to a grade.
- Thickness range0.10–0.35 mm
- StandardsGB · EN · JIS · AISI
- Grade equivalentsCross-referenced
In the field
CRGO in the power transformer core
From coil to wound core — what our Hi-B and Standard CRGO looks like on the way into a transformer.
Technical requirements
What power transformer specs typically call for
| Core loss (no-load loss) | Lowest available — Hi-B grades ≤ 0.85–0.90 W/kg at 1.7T/50Hz |
|---|---|
| Magnetic induction B8 | ≥ 1.90 T preferred for Hi-B, ≥ 1.88 T for Standard CRGO |
| Thickness | 0.23mm most common for large power cores; 0.27–0.30mm for mid-size units |
| Surface insulation | C5 or EP-2 glass-film coating, per GB/T 2521 or EN 10107 |
| Stacking factor | ≥ 0.965 (0.23mm) — affects effective core cross-section |
| Mill certification | Mill test certificate with every order, ISO 9001 / IATF 16949 |
Sizing a mid-size unit instead? See Distribution Transformers for the more cost-balanced spec — view distribution transformer steel →
How we work
From enquiry to your dock
A simple path from spec to delivery, built for overseas buyers.
Send your rating
Transformer kVA rating and target no-load loss, or a drawing.
Quote in 24h
Grade recommendation, pricing and availability within one business day.
Free samples
Test core loss and stampability, usually within a week.
Production & QC
Rolled, slit and tested to grade, with a mill certificate.
Export delivery
Moisture-proof packing and ocean freight to your port.
FAQ
CRGO for power transformers
Why do power transformers need Hi-B grades specifically?
Power transformers run near-continuously for decades, so no-load (core) loss is present around the clock regardless of load. Hi-B and laser-scribed grades cut that loss by 5–10% versus Standard CRGO, which compounds into significant energy savings over the transformer’s service life — often justifying the higher material cost.
What is “capitalized loss evaluation” and why does it matter for my grade choice?
Many utility and industrial buyers don’t award transformer bids on price alone. They apply a dollar-per-watt penalty to no-load and load losses (often called “A” and “B” factors) and add that to the purchase price to get a true lifetime cost. A transformer built with lower-loss Hi-B core steel often wins this comparison even at a higher upfront price, because the accumulated loss saving over 25+ years outweighs the difference.
What thickness should I use for a large power transformer core?
0.23mm is the most common choice for large power cores, since thinner laminations reduce eddy-current loss. 0.27–0.30mm is used on mid-size units where the loss penalty is more tolerable and cost matters more.
Can you match the grade on my existing transformer’s core steel?
Yes — send us the grade code or a datasheet from your current supplier and we’ll cross-reference it to our GB, EN, JIS or AISI equivalent and confirm the match.
What’s the lead time for Hi-B CRGO in bulk?
Quotes come within 24 hours. Common Hi-B widths often ship from stock in days; large or non-standard orders typically take a few weeks — tell us your volume and timeline and we’ll confirm.
Do you provide test data with each coil?
Yes — every order ships with a mill test certificate confirming core loss, induction and thickness, produced under ISO 9001 and IATF 16949.
Why buyers choose Zhongxin
Mill-grade CRGO, export-ready service
Wuxi Zhongxin Special Steel Co., Ltd. is a Chinese manufacturer and exporter of grain-oriented silicon steel, serving power transformer makers across Europe, the Americas, Asia and beyond.
Send your transformer rating — get a grade recommendation
kVA rating, target no-load loss, or a drawing — we’ll recommend a grade and quote in 24 hours.