The selection of magnetic materials for electric motors has become increasingly critical as industries demand higher efficiency, greater power density, and enhanced performance in compact packages.
With options ranging from traditional electrical steel to advanced alloys like Hiperco® and Hypocore®, understanding how material properties impact motor performance is essential for next-generation electric motors. Let's dive in.
Understanding Magnetic Material Requirements
In electric motors, soft magnetic alloys provide the medium for electromagnetic energy conversion, converting electrical input into mechanical output. Their selection is one of the most fundamental decisions in motor design.
These materials directly influence critical parameters through their inherent properties, including:
- Maximum torque and power output within size constraints
- Motor dimensions and weight for system integration
- Operational efficiency and heat generation
- Performance stability across varying conditions
- Manufacturing complexity and production costs
- Long-term reliability over the product lifecycle
Comparing Material Options
Let's examine how today's material options stack up, from conventional silicon steel to cutting-edge alloys that are reshaping motor design possibilities.
Silicon Steel (electrical steel)
Silicon steel, the most widely used magnetic material in conventional electric motors, offers an economical balance between cost and performance. Adding silicon to iron significantly increases electrical resistivity and reduces eddy current losses while maintaining reasonable saturation properties at a competitive price point.
Silicon steel typically comes in two primary varieties with distinct processing and performance characteristics:
- Non-oriented electrical steel: 2-3.5% silicon with uniform magnetic properties in all directions
- Grain-oriented electrical steel: 3-4.5% silicon with enhanced properties in one direction
While silicon steel offers good magnetic properties at a reasonable cost, it encounters significant limitations in demanding applications:
- Magnetic saturation limited to ~20 kilogauss
- Higher core losses compared to premium alternatives
- Diminishing performance at high frequencies
- Lower permeability characteristics
Hiperco® Alloys
Our Hiperco® family of iron-cobalt soft magnetic alloys represents the premium tier, offering exceptional magnetic performance for the most demanding applications. These specialized alloys combine carefully balanced compositions with sophisticated processing to achieve unmatched properties.
Hiperco® alloys provide several distinctive performance advantages that directly translate to enhanced motor capabilities:
- Highest magnetic saturation (up to 24 kilogauss) commercially available
- Superior permeability for maximum electromagnetic efficiency
- 25% higher magnetic induction than electrical steel
- 30% lower core losses
- Available in 0.1-0.5mm thicknesses
These enhanced material properties translate to substantial real-world performance benefits:
- 25% greater torque density
- 30% improvement in power density
- Up to 30% size reduction potential
- Enhanced thermal characteristics
- Extended motor lifespan
Hypocore® Alloys
Hypocore® represents a strategically positioned intermediate option between premium Hiperco® and conventional silicon steel. This low-cobalt alternative offers superior magnetic characteristics compared to standard electrical steel while maintaining a favorable cost structure for high-volume applications.
Key performance characteristics of Hypocore® include:
- Low coercivity, high permeability, increased electrical resistivity
- 3-4% higher magnetic induction than electrical steel
- 15-20% lower core losses
- Magnetic saturation of 21 kilogauss
- Optimized composition for electrical resistivity
Material Selection Framework
Selecting the optimal magnetic core material requires a systematic evaluation of application requirements against material properties, manufacturing considerations, and economic factors. The following framework offers a structured approach to material selection.
1. Performance Requirements Assessment
Begin the selection process by clearly defining what your motor needs to achieve. Account for these critical performance parameters:
- Required torque and power density within dimensional constraints
- Operating frequency range
- Efficiency targets and acceptable losses
- Size and weight limitations
- Thermal management capabilities
- Environmental conditions and service life
2. Frequency Considerations
The frequency at which your motor operates determines which materials will maintain efficiency and minimize losses. Here's how different frequency ranges align with material choices:
- Low-Frequency (50-60 Hz): Silicon steel may suffice for cost-sensitive applications
- Medium Frequency (400 – 800 Hz): Hiperco® offers substantial advantages and Hypocore® is an economical alternative with lower losses than silicon steel
- High-Frequency (>1kHz): Hiperco® with thin laminations delivers exceptional performance
3. Size and Weight Constraints
When every gram and millimeter counts, material selection becomes critical. Different industries and applications face varying levels of constraint, as shown below:
- Aerospace/eVTOL: Hiperco® enables critical size/weight reductions
- Automotive: Hypocore® balances performance and economics
- Industrial: Silicon steel is adequate where constraints are less restrictive
4. Thermal Management Considerations
The ability of a material to manage heat effectively directly affects motor reliability and performance. High-performance alloys (like Hiperco®) offer several thermal advantages, including the following:
- High-performance magnetic alloys generate substantially less heat through reduced core losses
- Advanced materials enable higher continuous power operation without excessive temperature rise
- Reduced thermal stress extends component life by minimizing thermal cycling
5. Economic Considerations
True material value extends beyond the initial purchase price to encompass the total cost of ownership, including all associated expenses. Consider these economic factors:
- Material acquisition costs, including raw materials and processing
- Manufacturing complexity and associated production costs
- Performance advantages that translate to operational benefits
- Lifetime operational savings through reduced energy consumption
- Warranty and maintenance implications affecting total cost of ownership
Application-Specific Material Selection
Different industries prioritize different performance characteristics based on their unique constraints and requirements. For example:
- Aerospace & eVTOL: Weight and size constraints make Hiperco® stand out, delivering 12-20% increased flight range, 20% higher payload capacity, and enhanced reliability for safety-critical systems.
- Electric Vehicles: Premium EVs use Hiperco® for maximum torque density, mid-range EVs benefit from Hypocore®'s balanced performance and cost, while commercial EVs may leverage enhanced materials for improved range.
- Industrial Applications: Where reliability matters most, advanced iron-cobalt materials like Hiperco® and Hypocore® reduce energy consumption, extend motor life, and enable smaller footprints, delivering substantial lifetime savings that justify higher initial costs.
Related Blog: Guide to Electric Motor Optimization: From Design to Testing
Manufacturing Considerations
Material selection decisions cannot be separated from manufacturing capabilities, as advanced magnetic materials require specialized processing expertise to realize their performance potential.
Traditional manufacturing methods encounter the following limitations when working with high-performance alloys:
- Dimensional changes during heat treatment
- Achieving tight tolerances requires expensive post-processing
- Conventional stacking methods compromise copper fill factors
- EDM cutting limits production volume and increases costs
Our integrated manufacturing approach overcomes these limitations through the following process optimizations:
- Precision strip hot rolling with dimensional stability controls
- Engineered heat treating and bonding processes
- Advanced lamination techniques ensuring consistent performance
- Automated stacking methods in controlled environments
- Comprehensive testing protocols at every production stage
Quality Assurance Framework
Maintaining consistent material performance requires comprehensive quality control throughout the production process. Our framework includes the following critical measures:
- Advanced material property verification throughout production
- Real-time dimensional monitoring systems
- Statistical process control for early deviation detection
- Complete production traceability
- Automated inspection systems
- Controlled environmental conditions during critical stages
Additionally, our AS9100 certification meets aerospace industry standards, ensuring consistent performance in applications where reliability is paramount.
The Path to Superior Performance
Selecting the right magnetic material directly impacts your electric motor's power density, efficiency, and overall performance. As applications become increasingly demanding, advanced materials like Hiperco® and Hypocore® alloys deliver the exceptional magnetic properties needed to meet these challenges while enabling smaller, lighter, and more efficient motor designs.
Want to learn more? Access our datasheets to learn how Hiperco® can optimize your electric motor performance. Contact Carpenter Electrification to discuss your specific application needs.