Magnetic Materials for Electric Transportation

The performance of high-power motors used in marine applications relies on appropriate magnet selection

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Originally published in Electric & Hybrid Marine Technology.

Electric transportation poses pressing design and manufacturing challenges – one of which is its high-power requirements. The electrification of all transportation would require more power than a standard electrical grid could provide on top of current demands. Permanent magnet motors have increasingly become the motor of choice in various applications as they benefit from superior energy efficiency and power-to-weight ratio. The efficiency of these motors is especially advantageous in battery-powered systems. The automotive and marine industries have embraced these motors in powertrains due to their impressive power density, efficiency and compact size. Their brushless design offers improved reliability and longevity over traditional induction motor designs.

Material choices

When considering materials for high-performance PM applications, neodymium iron boron (NdFeB) and samarium cobalt (SmCo) are widely used due to their high magnetic strength. However, they differ in several key aspects that can influence their suitability for various applications.

NdFeB magnets exhibit higher magnetic flux than SmCo magnets, which means they can deliver more magnetic force. This makes such magnets suitable for applications that require higher torque output with lighter weights, such as electric vehicles and wind turbines. However, NdFeB magnets have a lower resistance to high temperatures and are more prone to corrosion, which may require additional thermal management or protective coating in certain applications.

On the other hand, SmCo magnets offer superior temperature stability and corrosion resistance. For example, Arnold Magnetic Technologies’ Recoma 35E SmCo magnet materials, the most power-dense samarium cobalt magnet available, are engineered for the most demanding environments including high speed (in excess of 100,000 rpm), high temperature (150-250° C) and highly corrosive environments.

Unlike neodymium (Nd) magnets, which need high levels of rare dysprosium (Dy) to function at moderate temperatures, SmCo magnets use materials that are more widely available and are stable at temperatures well above the Curie point of NdFeB. This makes SmCo pricing more stable and less prone to rare earth market changes.

When there are supply concerns, it’s crucial to source domestically when possible. Companies such as Arnold Magnetic Technologies offer a broad-based source of supply for samarium cobalt magnets’ materials, including samarium cobalt made in the USA. Plus, Arnold’s recent partnership with Cyclic Materials provides another supply source for these critical resources. Arnold and Cyclic Materials are creating the world’s first circular supply chain for rare earth materials through reclamation.

In applications where high power density is a must, efficiency must be maximized. Precision-rolled thin metals, L-type laminated magnets and more help customers achieve higher efficient and power gains in their motor and transformer designs. Arnold has played a pivotal role in the electrification of transportation since the invention of the electric train. Today the company works with its customers to pioneer electric propulsion systems for space, air, watercraft, motorsport vehicles and heavy equipment.

About Arnold Magnetic Technologies

Based in Rochester, NY with an operating history of more than 125 years, Arnold is a leading global manufacturer of engineered solutions for a wide range of specialty applications and end-markets, including aerospace and defense, general industrial, motorsport, oil and gas, medical, and energy. From its Technology Center and manufacturing facilities located in the United States, the United Kingdom, Switzerland, and China, the company produces engineered magnetic assemblies in addition to high-performance permanent magnets, precision foil products, and highly loaded composites that are mission critical in motors, generators, sensors, and other systems and components. Based on its long-term relationships, the company has built a diverse and blue-chip customer base totaling more than 2,000 clients worldwide. For more information on Arnold, visit   

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