Magnetic Materials in electric Vehicles: Towards an efficient and sustainable future

In the first half of 2023, the global sales of electric vehicles reached 6.2 million, an increase of 12.4% compared to the same period last year.This reflects the prosperity and rapid growth of the electric vehicle market.Behind this trend, it is not only due to the increasing awareness of environmental protection, but also due to the advancement of new energy vehicle technology.

In addition, magnetic materials play a vital role in core components such as electric motors and sensors of electric vehicles, and the improvement of their performance has also contributed to the prosperity of the electric vehicle market.

What are the magnetic materials in electric vehicles?

According to statistics, electric vehicle components usually have about 20,000 parts, including thousands of magnetic components.The magnetic materials used in electric vehicles are mainly divided into soft magnetic and hard magnetic materials, which differ mainly in their coercivity.

Hard magnetic materials are also known as permanent magnets, which refer to magnetic materials that are not easily demagnetized after being magnetized by an external magnetic field.Soft magnetic materials are magnetic materials that are easily demagnetized after being magnetized by an external magnetic field.Permanent magnet motors are the most important application of magnetic materials in electric vehicles.

Generally, in permanent magnet motors, soft magnetic materials are used to manufacture the stator winding, while hard magnetic materials are used to manufacture the rotor.

Compared with electrically excited motors, permanent magnet synchronous motors use permanent magnets to replace the excitation winding of the rotor, and can maintain the magnetic field without being energized.It adjusts speed by changing voltage or resistance, which not only uses less materials such as silicon steel sheets and copper, but also reduces current loss and core loss.Therefore, permanent magnet synchronous motors have the advantages of energy efficiency, superior speed regulation performance, small size, light weight, and simple structure, but the disadvantage is high cost, poor reliability in high-frequency vibration, and easy demagnetization when the temperature difference is large.

Hard magnetic materials: The permanent magnetic materials used in electric vehicles are mainly neodymium magnets and hard ferrite . In permanent magnets, neodymium magnets outperform hard ferrite in terms of residual magnetic induction strength, intrinsic coercivity, and maximum magnetic energy product. Each new energy vehicle requires approximately 2.5kg of neodymium magnet material, mainly used for driving motors, ABS, EPS, etc. This material has excellent performance and can significantly improve motor energy efficiency and reduce energy loss. In addition, car speakers and various sensors are also components of neodymium magnets used in electric vehicles.

Hard Magnetic Materials neodymium magnets
Neodymium magnets

Although the performance of hard ferrite is poor, its price is very cheap.It is widely used in micro-motors with low performance requirements and wide available space.

Hard ferrite magnets

Soft magnetic materials: In electric vehicles, silicon steel is one of the important materials for motor cores.  It can effectively reduce the core loss and hysteresis loss , improving the efficiency and performance of the motor.In addition to motors, silicon steel can also be applied to electric vehicle charging piles, battery management systems, body structural components, and so on.

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Silicon steel

The iron-based amorphous alloy and silicon steel are in a competitive relationship.  At high frequencies, the permeability of silicon steel decreases, resulting in higher core losses, while the permeability of amorphous alloy remains almost unchanged.Therefore, amorphous alloy has advantages in high-frequency drive motors, but its disadvantages include brittle texture, difficult processing, high cost, and high vibration noise at high frequencies.

Iron-based amorphous alloy

Soft ferrite is a semiconductor with low magnetic permeability and high resistivity, which is beneficial for reducing core losses and increasing the operating frequency of the core.Due to their relatively low losses at high frequencies, they are widely used in the cores of transformers and inductors for electric vehicles.

Soft ferrite magnets

Future trends

BYD Electric Vehicles

The primary trend in the future development of electric vehicles is lightweighting.In order to achieve the goal of lightweighting, in addition to using lighter aluminum alloy materials for the body structure, improvements to the motor are also necessary.

Generally, new energy vehicles require 1-2 drive motors and a number of micro motors.Currently, each electric vehicle is equipped with an average of more than 40 motors, and some high-end electric vehicles use up to more than 100 motors.The maximum magnetic energy product of neodymium magnets can reach 52MGOe, which is 10 times that of ferrite.If all motors are replaced with neodymium magnet motors, the total motor weight will be reduced by 40%, and the occupied volume will be reduced by more than 50%.

Secondly, intelligence is another important trend in the development of electric vehicles.Intelligent electric vehicles require a large number of sensors and controllers to improve safety and comfort, and magnetic materials play an important role in them.For example, Hall sensors require the use of magnetic materials to detect changes in magnetic fields.Hall sensors are a type of sensor that relies on the Hall effect to achieve physical quantity conversion.In electric vehicles, it can sense information such as vehicle speed and driving distance by measuring the magnetic field changes of tire profiles.At the same time, it can also monitor key parameters such as motor speed, torque, phase, as well as monitor battery power, charging and discharging status.

Magnetic materials have always played an important role in the development of electric vehicles.With the technological advancement and iterative upgrading of magnetic materials, they will make greater contributions to the lightweight and intelligentization of electric vehicles.

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