Selecting the optimal magnet for electric motors directly impacts efficiency (up to 98% in premium designs), manufacturing costs (magnets account for 25-50% of motor material costs), and operational lifespan. With industries like EVs and industrial automation demanding higher power density, understanding these four magnetic properties is essential for engineers and designers.

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1. Remanence (Br): The Power Driver

Remanence (Br) measures residual magnetic flux density after magnetization, expressed in Tesla (T). Higher Br values enable:

• Compact designs: A 1.4T NdFeB magnet produces 40% more flux than a 0.4T ferrite magnet, reducing motor size.

• Higher torque: EV motors using N52-grade NdFeB (Br=1.48T) achieve 15% faster acceleration vs. ferrite alternatives.
  Trade-off: High-Br materials like neodymium are sensitive to demagnetization at >150°C.
  

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2. Energy Product (BHmax): Efficiency Multiplier

The energy product (kJ/m³ or MGOe) defines stored magnetic energy. Compare common materials:

• Ferrite (3–5 MGOe): Low-cost but requires 5x more volume than NdFeB.

• NdFeB (35–52 MGOe): Enables 90% weight reduction in drone motors.

• Samarium Cobalt (25–32 MGOe): Ideal for aerospace (stable at 300°C).

Case Study: A 10kW industrial pump motor switched from ferrite to NdFeB, cutting magnet weight from 4.2kg to 0.8kg while maintaining output.

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3. Intrinsic Coercivity (Hcj): Demagnetization Defense

Coercivity (kA/m) indicates resistance to external fields. Critical in applications like:

• EV inverters: High-frequency PWM signals create reverse fields up to 300kA/m.

• Wind turbines: Lightning strikes generate destructive magnetic pulses.

Rule: Select Hcj values 20–30% above the system’s maximum reverse field. For example, NdFeB grades like 48H (Hcj=1,120kA/m) outperform standard N42 (Hcj=955kA/m) in harsh conditions.

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4. Curie Temperature (Tc): Thermal Limits

The Curie point determines irreversible magnetic loss. Key thresholds:

Material	Tc (°C)	Safe Operating Temp (°C)
Ferrite	450	≤180
NdFeB	310	≤150
SmCo	800	≤300

Failure Example: A CNC machine motor using NdFeB reached 170°C due to poor cooling, causing 12% flux loss and $8,200/year in downtime.

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Material Selection Guide

Parameter	Ferrite	NdFeB	SmCo
Cost ($/kg)	3–5	50–100	120–200
Corrosion Resistance	High	Low*	High
Temp Stability	Good	Poor	Best
*NdFeB requires nickel/ epoxy coating.

Application-Based Recommendations:

• Budget Motors: Ferrite + increased stator slots.

• High-Speed Motors: SmCo for <0.1% flux loss at 250°C.

• Consumer Electronics: Coated NdFeB for miniaturization.

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Avoid These 3 Common Mistakes

1. Ignoring Dynamic Demagnetization: Test magnets under load (not just static Br).

2. Overlooking Machining Costs: Sintered NdFeB adds $20–50/kg for precision shaping.

3. Miscalculating Air Gaps: A 0.5mm error reduces flux by 9–15%.

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Need Custom Solutions?

Contact TECOMAG’s engineering team for:
✅ Free material analysis
✅ Demagnetization curve modeling
✅ ISO-certified prototyping
sales01@tecomag.net | info@tecomag.net