Can Synchronous Reluctance Motors End Our Dependence on Chinese Rare Earths?

Can Synchronous Reluctance Motors End Our Dependence on Chinese Rare Earths?

Synchronous Reluctance Motors: A Pathway to Reduce Rare Earth Dependence on China

Breaking Free from Rare Earth Constraints

The global electric vehicle and industrial motor industry faces a strategic vulnerability: heavy dependence on rare earth permanent magnets, predominantly controlled by China.

Synchronous reluctance motors (SynRMs) are emerging as a compelling alternative that could help manufacturers reduce their reliance on these critical materials while maintaining competitive performance.

China currently controls approximately 70% of global rare earth mining and over 90% of rare earth processing capacity.

The rare earth elements neodymium, dysprosium, and praseodymium are essential for manufacturing the powerful permanent magnets used in conventional electric motors.

This concentration of supply creates geopolitical risks and price volatility that manufacturers are increasingly seeking to avoid.

Synchronous reluctance motors operate on an entirely different principle. Instead of using permanent magnets to create magnetic fields, SynRMs utilize the magnetic reluctance of specially designed rotor structures.

The rotor contains layers of magnetic steel and air barriers arranged to create paths of varying magnetic resistance.

When the stator generates a rotating magnetic field, the rotor aligns itself with the path of least reluctance, producing torque without any permanent magnets.

Can Synchronous Reluctance Motors End Our Dependence on Chinese Rare Earths?

Technical Advantages and Market Adoption

Several major manufacturers have already committed to SynRM technology.

BMW’s fifth-generation electric drivetrain, introduced in models like the iX3 and i4, employs synchronous reluctance motors without rare earth magnets.
Renault has similarly invested in rare-earth-free motor technology for its electric vehicles.
Industrial motor manufacturer ABB has been a longtime advocate, offering SynRM solutions for industrial applications since 2011.
Japan Astemo announced on October 27 that it has developed a new rare earth-freeSynRM motor

The technology offers several strategic advantages beyond rare earth independence. SynRMs eliminate concerns about magnet demagnetization at high temperatures, a significant issue in permanent magnet motors.

They also provide better fault tolerance, as there are no magnets to create uncontrolled back-EMF during failures.

Manufacturing costs can be lower once production scales, as the rotor construction, while geometrically complex, uses only standard electrical steel.

However, challenges remain:

SynRMs typically require larger physical dimensions to achieve equivalent torque compared to permanent magnet motors, making packaging more difficult in space-constrained applications.
They also depend heavily on sophisticated control algorithms and power electronics to maintain efficiency.
The motor controller must continuously optimize current angles and magnitudes to achieve maximum torque per ampere, requiring more computational resources than simpler permanent magnet motor control.

Performance Characteristics and Future Outlook

Modern SynRMs achieve power densities approaching 85-90% of equivalent permanent magnet motors, a significant improvement from earlier generations. Efficiency at rated load typically reaches 93-96%, competitive with many permanent magnet designs. The technology performs particularly well in constant-torque applications and benefits from field-weakening capability that can extend the constant-power operating range.

The strategic importance of rare-earth-free motor technology continues to grow as electric vehicle production scales globally. Government initiatives in Europe and North America specifically encourage development of motors that reduce critical material dependencies. Research institutions are actively developing advanced rotor geometries, improved magnetic materials, and more efficient control strategies to further close the performance gap with permanent magnet motors.

While synchronous reluctance motors may not completely replace permanent magnet motors in all applications, they represent a viable alternative that can significantly reduce industry dependence on rare earth supply chains. As the technology matures and manufacturers optimize designs for specific use cases, SynRMs are likely to capture an increasing share of the electric motor market, particularly in applications where supply chain resilience is valued alongside pure performance metrics.

Detailed Comparison: Permanent Magnet Motors vs. Synchronous Reluctance Motors

Characteristic	Permanent Magnet Synchronous Motor (PMSM)	Synchronous Reluctance Motor (SynRM)
Magnetic Material	Requires rare earth magnets (NdFeB, SmCo)	No permanent magnets; uses electrical steel only
Rare Earth Dependence	High – dependent on neodymium, dysprosium	None – completely rare-earth-free
Supply Chain Risk	Significant geopolitical vulnerability	Reduced risk; materials widely available
Power Density	Excellent (100% baseline)	Good (85-90% of PMSM)
Torque Density	High – compact design possible	Moderate – requires larger volume for same torque
Efficiency at Rated Load	94-97%	93-96%
Efficiency at Partial Load	Excellent	Good to very good (controller-dependent)
Peak Efficiency Range	Broad operating range	Narrower, more dependent on control optimization
Rotor Construction	Simple – magnets mounted on/in rotor	Complex – multiple flux barriers and steel layers
Manufacturing Cost	Higher (expensive rare earth materials)	Potentially lower at scale (standard materials)
Manufacturing Complexity	Moderate (magnet handling challenges)	Higher (precise lamination geometries required)
Temperature Sensitivity	Magnets can demagnetize at high temperatures	Not temperature-sensitive (no magnets)
Maximum Operating Temperature	Limited by magnet grade (150-200°C typical)	Higher capability (limited by insulation only)
Control Complexity	Moderate – simpler field-oriented control	High – requires sophisticated optimization
Back-EMF at High Speed	High – can complicate control and safety	Lower – better fault tolerance
Field Weakening Capability	Limited by magnet flux	Good – purely controlled by stator current
Constant Power Speed Range	Moderate	Wide range possible
Acoustic Noise	Low to moderate	Moderate to high (torque ripple)
Torque Ripple	Low with proper design	Higher – requires careful design and control
Starting Torque	Excellent	Good (requires position sensing)
Overload Capability	Good	Good to excellent
Fault Tolerance	Lower – magnet flux always present	Higher – no uncontrolled fields
Recycling/End-of-Life	Complex – rare earth recovery needed	Simpler – standard steel recycling
Environmental Impact	Higher (rare earth mining impact)	Lower (no rare earth mining required)
Best Applications	High-performance EVs, compact drives, servo systems	Industrial drives, cost-sensitive EVs, high-temperature environments

This comparison demonstrates that while permanent magnet motors currently hold advantages in power density and compactness, synchronous reluctance motors offer a strategically important alternative that eliminates rare earth dependence while delivering competitive performance in many applications.

The choice between technologies increasingly depends on specific application requirements, supply chain priorities, and long-term strategic considerations rather than pure technical performance alone.