CRGO vs CRNGO: choosing electrical steel for transformers and motors
How grain orientation changes magnetic behaviour, why transformer cores and rotating machines use different types — and which details to include when you ask for a quotation.
In this article 8 sections
Every transformer and every electric motor relies on a magnetic core, and almost every one of those cores is built from thin sheets of electrical steel. Two families dominate: grain-oriented steel (CRGO, or simply GO) and non-grain-oriented steel (CRNGO, or NGO). They look alike on a coil — but they are engineered for very different magnetic jobs.
This guide explains the difference in plain language, shows how manufacturers describe performance, and lists the details that make a quotation request precise. It is written for procurement teams and engineers who need to specify the right material without wading through a full technical manual.
Key takeaways
- GO is optimised for magnetic flux in one direction — the rolling direction — which suits transformer cores.
- NGO behaves similarly in every direction, which suits the rotating fields in motors and generators.
- For GO, buyers compare maximum core loss and minimum magnetic induction at a stated thickness.
01What makes steel “electrical”
Electrical steel is iron alloyed with silicon and rolled into thin, insulated sheet. The silicon raises the steel’s electrical resistivity, and the thin gauge plus an insulating coating on every sheet keep circulating currents small. Both matter because a magnetic core is magnetised and demagnetised many times every second when it carries alternating current.
Each of those cycles costs a little energy, released as heat. Engineers call this core loss (or iron loss), and it has two main parts:
- Hysteresis loss — the energy needed to repeatedly re-align the steel’s magnetic domains.
- Eddy-current loss — small currents induced inside the sheet itself. Thinner sheets and higher resistivity reduce them.
The other headline property is how easily the steel can be magnetised — its magnetic induction (flux density) at a given field strength. A higher induction lets a designer reach the working flux with less current and, often, a smaller core.
02Grain-oriented electrical steel CRGO / GO
Steel is made of tiny crystals, or grains. In grain-oriented steel, a carefully controlled sequence of rolling and annealing steps lines most of those crystals up so that their easiest direction of magnetisation runs along the rolling direction of the strip. The result is very low core loss and high induction — but only when the flux follows that direction.
That is exactly what happens in a transformer core: the strips are cut and stacked so that the flux travels along the limbs and yokes, parallel to the rolling direction. This is why GO steel is the standard core material for power and distribution transformers.
The supplied manufacturer manual groups GO steel into three types, each identified by a letter in the grade code:
Type classification as described in the Baosteel grain-oriented electrical steel technical manual.
03Non-grain-oriented electrical steel CRNGO / NGO
In non-grain-oriented steel the crystals are deliberately left without a preferred direction, so the magnetic properties are much the same whichever way the flux runs through the sheet. It cannot match GO steel along the rolling direction — but it does not have a “weak” direction either.
That matters in rotating machines. In a motor or generator, the magnetic field rotates with the rotor, so the stator and rotor laminations are magnetised in every direction in turn. NGO steel is therefore the usual choice for motors, generators, compressors and many small transformers and chokes where the flux path is not a simple straight line.
NGO steel is commonly supplied fully processed (magnetic properties developed at the mill, ready to punch) or semi-processed (the user anneals the laminations after punching). Which one you need depends on your own production route.
NGO grade data is not yet published on this site. See the CRNGO page for the specification structure.
Flux that runs in one direction favours grain-oriented steel. Flux that rotates calls for non-grain-oriented steel.
04Side by side
A qualitative comparison of the two families. Exact values always depend on the grade, thickness and test standard.
| Aspect | Grain-oriented · CRGO / GO | Non-grain-oriented · CRNGO / NGO |
|---|---|---|
| Grain structure | Aligned with the rolling direction | No preferred direction |
| Magnetic behaviour | Best along the rolling direction | Similar in all directions |
| Flux path | Fixed, along the strip | Rotating or changing direction |
| Typical equipment | Power & distribution transformers, reactors | Motors, generators, compressors |
| Values buyers compare | Max core loss P1.7/50 · min induction B8 | Core loss & polarisation per the applicable standard |
| Typical supply form | Coil or slit coil, insulated | Coil or slit coil, insulated |
05Reading the numbers
Grain-oriented grades are compared on two headline values, both measured under defined test conditions:
P1.7/50- Core loss, in W/kg, at a peak flux density of 1.7 T and a frequency of 50 Hz. A grade’s figure is the maximum guaranteed by the manufacturer — lower is better.
B8- Magnetic flux density, in tesla (T), reached at a field strength of 800 A/m. The figure is a minimum — higher is better.
Manufacturers encode these values in the grade name. In the supplied manual, B27R090 reads as: manufacturer prefix B, thickness 0.27 mm, type R (domain-refined high induction), and maximum core loss 0.90 W/kg at P1.7/50.
Sample grades · GO electrical steel
Thickness, core loss & induction
| Grade | Type | Thickness mm | Max core loss P1.7/50 W/kg | Min induction B8 T |
|---|---|---|---|---|
| B27G120 | GConventional | 0.27 | 1.20 | 1.80 |
| B30G120 | GConventional | 0.30 | 1.20 | 1.80 |
| B27P095 | PHigh induction | 0.27 | 0.95 | 1.88 |
| B30P105 | PHigh induction | 0.30 | 1.05 | 1.88 |
| B23R080 | RDomain-refined HI | 0.23 | 0.80 | 1.87 |
| B27R090 | RDomain-refined HI | 0.27 | 0.90 | 1.87 |
Two patterns stand out in the sample: at the same thickness, the high-induction and domain-refined types show lower maximum loss and higher minimum induction than the conventional type; and within a type, thinner material shows lower loss, because eddy currents are smaller in a thinner sheet. The standard thicknesses listed in the manual are 0.23, 0.27, 0.30 and 0.35 mm.
06Choosing by application
The starting point is always the equipment and the design engineer’s loss and induction targets. As a general orientation:
If you are unsure which family or grade fits, send the application and your design targets with the enquiry — the grade can be agreed per enquiry.
07What to put in your RFQ
A complete request avoids back-and-forth and makes quotations comparable. For electrical steel, include:
- TypeGO (CRGO) or NGO (CRNGO)
- Grade or targetsA grade code, or max core loss and min induction
- StandardThe standard the grade should be tested to
- Thickness × widthIn mm, plus whether slitting is needed
- Coil ID & weightInside diameter and maximum coil weight
- CoatingInsulating coating type, if specified
- QuantityTonnes, and whether split shipments are possible
- Destination & documentsPort or city, and documents required with shipment
08Sources & attribution
Baosteel — Grain-oriented electrical steel technical manual. Source of the type classification (G / P / R), sample grade values, standard thicknesses, test basis and application fields quoted above. Values are reproduced as reference data and must be approved before publication.
General explanations in this article are educational and do not form a product specification. Grades actually offered, and their guaranteed values, are confirmed per enquiry.
