Magnetic materials in electric vehicles are essential for improving vehicles’ performance and efficiency. These materials have been used in various key components and systems.
Definition of Magnetic Materials
Magnetic materials are those that exhibit ferromagnetism or ferrimagnetism and have practical application value. A key difference between magnetic and other materials is that they respond sensitively to an external magnetic field.
Classification of Magnetic Materials
Magnetic materials can be classified into hard magnetic materials and soft magnetic materials based on their functionality.
Soft Magnetic Materials
Definition: Soft magnetic materials are easily magnetized under an external magnetic field and quickly lose their magnetism once the field is removed.
Characteristics: High magnetic permeability, low coercivity, and low residual magnetism.
Types: Silicon steel, iron-nickel alloys, soft magnetic ferrites.
Hard Magnetic Materials
Definition: Hard magnetic materials are those that, once magnetized under an external magnetic field, retain a strong magnetic field even after the removal of the magnetic field.
Characteristics: High coercivity, high residual magnetism, and long hysteresis loops.
Types: Neodymium iron boron (NdFeB) magnets, samarium cobalt alloys, hard magnetic ferrites.
Performance Evaluation for Magnetic Materials in Electric Vehicles
The performance of magnetic materials is measured by the following indicators:
Stability: Maximum magnetic energy product is the key parameter. Higher values indicate stronger magnetic fields and better ability of the material to maintain its magnetic properties.
Demagnetization Resistance: The key parameter is intrinsic coercivity. Higher values indicate better resistance to demagnetization and higher efficiency.
Temperature Resistance: The key parameters are intrinsic coercivity, maximum operating temperature, and Curie temperature. Higher values indicate better temperature resistance and greater stability of magnetic material properties.
Hard Magnetic Materials in Electric Vehicles
Neodymium Magnets
Neodymium iron boron (NdFeB) magnets, composed mainly of Nd2Fe14B, are known for their high residual magnetism and high coercivity. This material significantly enhances motor efficiency and reduces energy loss. Each electric vehicle typically requires about 2.5 kg of NdFeB magnets, which are mainly used in drive motors, ABS, EPS, and other components.
Core Applications (Motors): NdFeB magnets are used in the rotor of permanent magnet motors. These magnets are characterized by high magnetic energy product, high intrinsic coercivity, and high residual magnetism, making them widely applicable in improving electric vehicle performance.
Improved Driving Performance: As the core part of the motor, NdFeB magnets provide a strong magnetic field, enabling the motor to generate more torque and power output in a smaller size. This means that electric vehicles can accelerate faster and reach the same speed with more efficiency.
Greater Range: Due to the high magnetic energy product and residual magnetism, electric vehicles can achieve better energy efficiency with the same battery capacity, extending the vehicle’s range.
Lightweight Design: To improve energy efficiency and range, electric vehicles emphasize weight control. NdFeB magnets offer strong magnetic performance, which allows for higher power and torque density in motors while reducing the overall weight of the vehicle.
Soft Magnetic Materials in Electric Vehicles
Ferrite
Soft magnetic ferrites are ferrimagnetic oxides primarily composed of Fe2O3, manufactured using powder metallurgy. They are divided into several types, including Mn-Zn, Cu-Zn, and Ni-Zn ferrites, with Mn-Zn ferrites being the most widely used.
Soft magnetic ferrites, due to their excellent high-frequency electrical characteristics, relatively low cost, and ease of shaping, are widely used in electric vehicle applications such as OBC devices, EV charging equipment, HEV power system power conversion, DC-DC converters, and battery management systems.
Core Applications (DC-DC Converters): As the use of 42V automotive power systems increases, there is a growing demand for DC-DC converters to achieve voltage conversion. At the same time, assembling more electronic circuits in a limited space can lead to electromagnetic interference. To ensure the reliable operation of automotive electronic systems, high-conductivity soft magnetic ferrite cores are often used in automotive circuits to resist interference.
Silicon Steel
Silicon steel is an iron-silicon alloy made by adding a small amount of silicon (typically less than 4.5%) to pure iron. It possesses high magnetic permeability, low hysteresis loss, and low iron loss, making it an essential material in electric motors. As soft magnetic materials in electric vehicles, silicon steel helps reduce iron losses and hysteresis losses, thereby improving the efficiency and performance of motors. Silicon steel can also be applied in charging stations, battery management systems, and body structure components of electric vehicles.
Core Application (Motors): Due to constraints on vehicle space and battery capacity, the demand for high-performance magnetic materials in motors has increased. These materials are required to have high saturation flux density, high magnetic induction strength, low losses (especially low iron loss under mid-frequency conditions between 400-1,500 Hz), excellent mechanical properties, fatigue resistance, good machinability, and high cost-effectiveness. Cold-rolled non-oriented silicon steel is still widely used to meet these requirements.
Metallic Soft Magnetic Powder Cores
Metallic soft magnetic powder cores are made by compressing magnetic powder coated with an insulating medium. These materials combine the advantages of metal soft magnetic materials and soft magnetic ferrites. Due to the use of ferromagnetic particles in the powder, they have high saturation magnetic induction, while the insulating layer ensures higher electrical resistivity.
Core Applications (Charging Equipment): Metallic soft magnetic materials are mainly used in charging stations, on-board AC/DC chargers, and on-board DC/DC converters in the electric vehicle sector. The amount of metal soft magnetic powder cores varies across different types of electric vehicles.
For hybrid vehicles, which require significant step-up inductance, approximately 2.5 kg of metal soft magnetic materials are needed.
For 800V pure electric vehicles, which require a step-up module in the charging equipment, about 2 kg of metal soft magnetic materials are used.
For 400V pure electric vehicles, need only around 0.7 kg of metallic soft magnetic materials.
Extensively used in electric vehicle motors and other components, magnetic materials in electric vehicles play an increasingly important role in the development of the automotive industry.
Magnets Manufacturer
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