Neodymium Vs. SmCo Magnets For Hybrid Vehicles

Electric cars dominated by permanent magnets

　　The electrification of vehicles is a growing market for rare earth magnets. It is estimated that the consumption of rare earth magnets in transportation will increase from 7,000 tons in 2015 to 17,000 tons in 2020. Government directives to reduce pollution and high gasoline prices are pushing users to buy more environmentally friendly vehicles. Permanent magnet motors are currently the first choice for high-performance automotive applications. The rotor's balanced magnetic field and lower stator current requirements, coupled with very powerful position control, can improve motor efficiency. Two common choices in electric vehicle applications are neodymium magnets and sa cobalt magnets, each of which has its advantages.

　　SMCO VS. NEO: Which one performs better?

　　Temperature considerations

　　The decision between SmCo and Neo magnets usually depends on temperature. The high temperature of the vehicle transmission system requires magnets that can resist demagnetization. In most cases, this requires the use of sa cobalt magnets. The thermal demagnetization of SmCo magnets is lower than that of traditional neodymium-based magnets. (Consider that the reversible temperature coefficient of SmCo is 0.035%/C°, and neodymium is 0.10%/C°.)

　　The figure below shows the relationship between the residual magnetic flux density (Br) and temperature of different magnet materials and grades. Even if a neodymium magnet has a high residual magnetic flux density at room temperature, it will quickly cross the SmCo wire.

　　The four-pole motor is designed to operate in the engine compartment of a vehicle, and the ambient temperature of the engine compartment can be in any temperature range between -40°C and 125°C. This may cause the internal temperature of the machine to exceed 180°C. Must be designed within this temperature range will lead to a large performance difference in the performance of the magnet. In other words, for the same input current, a machine running at room temperature will have more torque than a machine running at 180°C.

　　Compared with neodymium magnets, sa cobalt magnets have a smaller demagnetization value, so their operating characteristics are much flatter over the entire temperature range. Temperature stability leads to stable output performance of the four-pole motor.

　　Neodymium 38EH magnet mar cobalt R35E magnet

　　Average torque at 20°C 2.3Nm 2.14Nm

　　Average torque at 180°C 1.86Nm 1.99Nm

　　Cost considerations

　　Neodymium iron boron (NdFeB) magnetic material has a high content of s, which is an extremely rare and expensive rare earth element. On the other hand, cobalt is easier to obtain and therefore more cost-effective.

　　Final decision

　　Despite its limitations, neodymium magnets are still the highest energy product of any material today and can be found in a variety of applications. When deciding whether to use Neo magnets or SmCo magnets, please carefully consider the maximum temperature of the application, the required magnetic output at the typical use temperature, and the total cost of the system.