A practical material table and selection guide for silicon steel sheets used in motor stator cores, rotor cores, servo motors, industrial motors, compressor motors, high-speed motors and high-efficiency electric drive systems.
Silicon steel, also called electrical steel, is selected mainly by sheet thickness, core loss, magnetic flux density, coating type, punching quality and supply stability. The correct grade helps reduce iron loss, temperature rise, no-load current, vibration and efficiency risk.
Most motor cores use non-oriented electrical steel because the magnetic field rotates in the stator and rotor. Grade choice should be connected with electrical frequency, flux density, motor speed, stamping process and target efficiency.
Cost-effective non-oriented silicon steel for general industrial motors, pumps, fans and compressors.
Lower-loss electrical steel for higher efficiency motors, servo motors and compact motor cores.
Used when high electrical frequency requires stronger eddy current loss control.
Rotor-focused electrical steel for high-speed permanent magnet motors and IPM rotors.
Selected when lower magnetizing current or better magnetic response is important.
Mainly used in transformers, not typical rotating motor cores, because its magnetic properties are directional.
The values below are approximate reference ranges for early material screening. Different steel mills and standards may use different test conditions, so final design should use the confirmed datasheet and sample core test results.
| Material Grade / Family | Typical Thickness | Core Loss Direction | Typical B50 Direction | Typical Motor Use | Selection Notes |
|---|---|---|---|---|---|
| 50W1300 / 50A1300 | 0.50 mm | Higher loss, economical grade | Good magnetic induction for cost level | Small motors, low-cost fans, appliances, low-duty equipment | Use where cost is more important than premium efficiency. |
| 50W800 / 50A800 | 0.50 mm | Moderate loss | Good general magnetic performance | General motor stators and rotors, pumps and fans | Common economy-to-standard choice for industrial applications. |
| 50W600 / 50A600 | 0.50 mm | Better than economy grades | Balanced B50 and cost | Industrial motors, compressors, HVAC motors | Useful when efficiency requirement is higher but cost still matters. |
| 50W470 / 50A470 | 0.50 mm | Low-loss standard 0.50 mm grade | Good flux density for general motors | Higher-efficiency industrial motors, servo outer diameter limited designs | Common balance between performance, availability and stamping cost. |
| 50W400 / 50A400 | 0.50 mm | Lower loss premium 0.50 mm grade | Good magnetic loading | Premium efficiency motors and lower no-load loss designs | Check supply stability and price before production selection. |
| 35W440 / 35A440 | 0.35 mm | Lower eddy current loss than 0.50 mm grades | Good motor-grade B50 | Servo motors, compact motors, higher-speed industrial motors | Good first step when 0.50 mm material causes too much iron loss. |
| 35W360 / 35A360 | 0.35 mm | Low loss | Good efficiency balance | Servo motors, compressors, EV auxiliary motors | Often used for improved efficiency without moving to very thin gauges. |
| 35W300 / 35A300 | 0.35 mm | Lower loss premium 0.35 mm grade | Good magnetic performance | High-efficiency motors, permanent magnet motors, precision drives | More sensitive to punching quality, burr and coating damage. |
| 35W250 / 35A250 | 0.35 mm | Very low loss for 0.35 mm family | Good B50, grade-dependent | Premium servo motors and high-efficiency motor cores | Use when loss target is demanding and volume supports material cost. |
| 30W230 / 30A230 | 0.30 mm | Low loss at higher frequency | Depends on supplier grade | High-speed motors, compact drives, traction auxiliary motors | Requires careful stamping, lamination handling and stacking control. |
| 27W230 / 27A230 | 0.27 mm | Low eddy current loss | Good for high-frequency operation | High-speed PM motors, compressor motors, servo motors | Check tool wear, burr height, stacking cost and lead time. |
| 25W130 / 25W120 | 0.25 mm | Very low loss thin gauge direction | Supplier and grade dependent | High-efficiency traction, high-speed and high-frequency motor cores | Often needs premium process control and careful cost review. |
| 20W120 / 20W100 | 0.20 mm | Ultra-thin low-loss direction | Lower or grade-dependent B50 possible | Very high-speed motors, aerospace-type motors, special drives | High cost, difficult stamping, fragile handling and supply constraints. |
| M19 / M27 Family | Commonly 0.35-0.50 mm | Standard motor electrical steel family | Good general motor performance | North American design references, general motor cores | Do not assume exact equivalence with W/A grades without datasheet comparison. |
| High-Strength NOES | 0.25-0.50 mm | Moderate to low loss depending on grade | May trade magnetic performance for strength | IPM rotors, high-speed rotors, traction motor rotors | Review centrifugal stress, bridge strength, magnet pocket tolerance and loss. |
This matrix connects silicon steel grade selection with motor type, electrical frequency, efficiency target and manufacturing route.
| Motor / Core Application | Recommended Material Direction | Design Driver | Common Process | Inspection Focus |
|---|---|---|---|---|
| General Industrial Motor | 50W600, 50W470, M19 / M27 family | Cost, availability, stamping productivity, acceptable iron loss | Progressive stamping, interlock, welding or riveting | Burr height, stack height, coating resistance, slot geometry |
| Premium Efficiency Motor | 50W400, 35W360, 35W300 | Lower no-load loss and reduced temperature rise | Precision stamping, bonding or controlled interlock | Core loss, lamination short, coating damage, stacking factor |
| Servo Motor Stator | 35W300, 35W250, 30W230 | Dynamic response, compact size, low iron loss | Precision stamping, adhesive bonding, insulation control | Slot accuracy, burr, core loss, noise and vibration risk |
| High-Speed PM Motor | 30W230, 27W230, 25W130 or suitable high-strength grade | High electrical frequency, rotor stress, low eddy current loss | Fine stamping, bonding, rotor sleeve or shrink-fit assembly | Rotor strength, runout, balance, burr and pocket tolerance |
| IPM Rotor Core | High-strength NOES or low-loss rotor grade | Magnet pocket bridge strength, leakage flux, speed safety | Stamping, skewing, stacking, magnet insertion, sleeve retention | Bridge width, pocket tolerance, crack risk, lamination burr |
| Compressor Motor | 35W360, 35W300, 27W230 depending on speed | Efficiency, heat, acoustic noise, oil/refrigerant environment | High-volume stamping, automated stacking and assembly | Core loss repeatability, dimensional stability, burr and noise |
| Traction / EV Motor | 35W250, 30W230, 27W230, high-strength NOES | High efficiency, high speed, thermal margin and rotor safety | Precision stamping, bonding, stress review, balance control | Loss at actual frequency, stress, coating, stack factor, traceability |
A good silicon steel grade can still perform poorly if stamping, coating, stacking or assembly is not controlled. Material selection and process validation should move together.
Confirm frequency, speed, flux density, torque target, thermal limit and efficiency requirement.
Compare thickness, iron loss, B50, coating, strength, availability and price.
Check stamping burr, coating damage, stack method, bonding, welding or interlock influence.
Measure stack height, core loss, insulation resistance, dimensional tolerance and assembly fit.
Compare grades at the actual frequency and flux density. A 50 Hz catalog value may not represent high-speed motor behavior.
Thinner sheets reduce eddy current loss but increase material cost, stamping difficulty and stack assembly cost.
High B50 helps magnetic loading, but loss, temperature and rotor strength must still be balanced.
Coating must survive stamping and stacking. Interlaminar shorts increase loss and local heating.
Burrs affect slot fill, stack height, insulation damage, lamination shorting, noise and assembly tolerance.
Laser-cut prototype laminations may show different edge damage and loss compared with stamped production parts.
Non-oriented silicon steel has more balanced magnetic properties in different directions and is widely used in motors with rotating magnetic fields. Grain-oriented silicon steel is optimized along the rolling direction and is mainly used in transformers.
Not always. Lower loss usually improves efficiency, but the final choice must also consider B50, sheet thickness, stamping quality, mechanical strength, price, availability and actual operating frequency.
Thin sheets require more laminations for the same stack height, tighter stamping control, higher tooling care and more handling effort. They are chosen when lower eddy current loss justifies the cost.
Sometimes yes, but high-speed rotors may need high-strength electrical steel or a different grade because rotor bridges, magnet pockets and centrifugal stress create mechanical risks.