Every EV traction motor is a stack of 0.35–0.50 mm laminations punched from non-oriented electrical steel — and the stack only performs as well as the strip's core loss, coating and burr control allow.
The rotor and stator of an EV motor are stacks of thin laminations because a solid iron block would heat itself into uselessness with eddy currents. Non-oriented electrical steel is the material built for that job: low enough core loss to stay cool at 10,000+ rpm, isotropic enough to magnetize in every direction the rotating field demands, and thin enough that the lamination stack packs maximum flux per unit volume.
The workhorse NO grade for traction motors: 0.50 mm, core loss ≤ 4.70 W/kg at 50 Hz / 1.5 T. Balanced cost and loss for mainstream passenger-car drive motors.
Default for most EV traction stators and rotors.Lower loss at the same gauge, or thinner gauge at similar loss. As motor speeds and inverter frequencies climb, the thinner and lower-loss grades pay back in range and thermal margin.
Choose 350/300-class when efficiency targets exceed the baseline.Grain-oriented (GO) steel is superb in one rolling direction but poor across it. A motor field rotates, so the core needs equal magnetics in all directions — that is precisely what the NO designation guarantees.
NO steel is the only family that fits a rotating field.Indicative values for traction motor programs; the final spec is agreed at RFQ against your motor design and target efficiency class.
| Parameter | Typical value | Why it matters |
|---|---|---|
| Strip thickness | 0.35 – 0.50 mm | Thinner laminations cut eddy-current loss at high inverter frequencies |
| Core loss (50WW470) | ≤ 4.70 W/kg @ 50 Hz / 1.5 T | Iron loss = heat = range loss; the grade's defining guarantee |
| Punch burr | ≤ 0.02 mm | Burrs short laminations together and raise eddy loss in the stack |
| Interlamination resistance | ≥ 5 Ω·cm² (coating performance) | Insulating coating keeps eddy currents inside each lamination |
| Magnetic isotropy | Equivalent B in all in-plane directions | Rotating field sees equal permeability on every axis |
| Stacking factor | High, via uniform gauge + thin coating | More steel per unit stack volume = more flux = more torque density |
| Surface / coating | Insulating coating, intact through slitting | Coating damage at the slit edge becomes interlamination shorts |
| Width / coil form | Slit to lamination-press width | Stator and rotor blanks index off exact strip width |
Core loss, coating and magnetics are confirmed on the MTC per heat. Interlamination resistance is a coating-system property; the ≥ 5 Ω·cm² figure is a practical production threshold — confirm the governing requirement with your motor spec.
All supplied with coating, slit to width. Choose by motor speed, efficiency target and cost envelope.
| Grade | Thickness | Core loss class | Typical use in the EV |
|---|---|---|---|
| 50WW470 | 0.50 mm | ≤ 4.70 W/kg | Mainstream passenger-car traction stators and rotors |
| 50WW350 | 0.50 mm | ≤ 3.50 W/kg class | Higher-efficiency motors, longer-range packs |
| 35WW300 | 0.35 mm | ≤ 3.00 W/kg class | High-speed motors, premium efficiency targets |
| 50WW400 | 0.50 mm | ≤ 4.00 W/kg class | Cost-efficient middle band for hybrid drives |
| B50A470 (Baosteel equivalent) | 0.50 mm | 470-class | Same material family under the Baosteel designation |
Core loss values are the grade's guarantee class per the Chinese GB/T 2521-2 style designation; exact guaranteed values follow the latest revision of the governing standard and are confirmed per heat on the MTC.
Lamination production looks simple — punch, stack, done — until the motor test bench disagrees. These are the failure modes and what we control on the strip.
Punch burr on the tooth edge bridges the coating and raises eddy loss. Fix: consistent gauge and surface let the die hold a sharp edge — burr ≤ 0.02 mm is the target we design the slit edge and flatness for.
A damaged slit edge becomes an interlamination short at the stack periphery. Fix: burr-managed slitting with coating-integrity checks on the delivered width.
Gauge scatter changes the stack height and the motor's flux path. Fix: precision-rolled electrical steel with a tight, documented thickness tolerance.
Shear stress at the punched edge degrades permeability locally. Fix: clean tooling and soft strip condition — plus stress-relief annealing on your side where the design allows it.
The motor core is one line in a wider EV bill of materials. Match your component below and confirm at RFQ.
50WW470 / 50WW350 / 35WW300 for stator and rotor laminations — the core of this page. Electrical steel family →
For motor frames, end plates and rotor shafts, precision strip and fine blanking steel carry the mechanical load. Fine blanking range →
For sensor rings and magnetic yokes where saturation flux matters more than loss. Electrical family →
A typical 150 kW traction motor stator, described the way it runs.
The stator is a stack of about 400 laminations, each a 200 mm ring with 48 slots, punched from 0.35 mm 35WW300 strip for a high-speed motor. The coil arrives slit to 210 mm width; a high-speed press punches one lamination per stroke, stacking them with a rotation between layers to spread tolerance, then the stack is welded or bonded and the winding goes in. On the test bench the motor is measured for iron loss at rated speed and flux — and the number has to match the design simulation.
The gap between simulation and bench is where strip quality shows up: burr that shorts the stack, coating that failed at the slit edge, gauge scatter that changed the stack height. Each one quietly raises the loss number the customer pays for in range. Our job is to deliver the strip so the stack performs like the datasheet: core loss guaranteed, coating intact, gauge uniform, edges clean. That is the entire product, and the MTC documents every line of it.
If your motor sits in the 0.35–0.50 mm NO envelope, send the lamination drawing and we confirm grade, loss class, coating and a trial-coil plan.
Related reading: core loss in NO electrical steel — what the datasheet number really means, and why punching burr costs you efficiency in the stack.
These grade families share material, processing or application territory with the topic on this page.
Invar / Kovar / Elinvar / Nichrome precision alloys for electromagnetic, thermal-bimetal and resistance applications.
Send the lamination drawing, thickness, loss class and quantity. Our engineers reply within one working day with grade match, coating confirmation and a trial-coil option.