New energy vehicle drive motor and non-oriented silicon steel

The driving power of new energy vehicles, especially electric vehicles of class B and above, is generally above 180kW, and two or more sets of electric drive systems need to be equipped. As the proportion of high-end electric vehicles continues to increase, the installed capacity of new energy drive motors will further increase. With the advantages of high power density, low energy consumption, small size, and light weight, permanent magnet synchronous motors are the most widely used in new energy vehicles, accounting for 94.4% of the total installed capacity in 2021. Drive motor is one of the three core components of new energy vehicles, and its future development direction is high speed and high power. This requires the motor to reduce the volume, weight and iron loss of the motor as much as possible under the same power, but reducing the volume and weight of the motor will lead to a reduction in the torque of the motor, so the speed of the motor needs to be increased. For example, the speed of the Prius2015 motor is almost three times that of the Prius2004 motor, while the peak torque shows a decreasing trend. Through the cooperation of the high-speed motor and the gearbox, the high-speed low-torque input is transformed into a low-speed high-torque output, thereby achieving the purpose of driving new energy vehicles.

The high-speed and high-power drive motors also put forward higher requirements for motor materials, especially the stator and rotor cores made of laminated non-oriented silicon steel sheets, which not only directly determine the motor power, torque, iron consumption, temperature The upgrade also affects the cruising range of new energy vehicles. For example, the Nissan Leaf II, which was launched in Japan, North America, and Europe in 2018, has a battery capacity of only 40kWh, but a cruising range of up to 400km, which is the same as the Tesla Model S with a battery capacity of 60kWh. This is because Nissan Leaf II uses a permanent magnet synchronous motor as the drive motor, which is excited by permanent magnets and does not require excitation current, so there is no excitation loss, low loss, and high efficiency. In addition, the stator and rotor iron core of the Nissan Leaf II drive motor is made of laminated silicon steel sheets with a thickness of 0.25mm, which can reduce iron loss and further improve motor efficiency. The drive motor core of the 2016 BMW i3 is made of laminated silicon steel sheets with a thickness of 0.27mm. There are a large number of weight-reducing holes in the rotor core to reduce the weight of the motor and increase the power density of the motor. Therefore, in order to improve the efficiency and power density of the motor, the silicon steel sheet for the motor has been reduced from the traditional 0.35mm and 0.50mm to 0.25mm and 0.27mm. It is foreseeable that with the increase of motor speed, silicon steel with thinner specifications and lower iron loss will be gradually applied to new energy vehicle drive motors.

The cold-rolled non-oriented silicon steel sheet used to manufacture the stator and rotor cores of drive motors is the key soft magnetic material that determines the conversion of power and energy. The iron loss generated in the iron core is an important part of the motor loss, especially when the motor is running at a high speed, the proportion of iron loss to the total loss increases significantly. In the ultra-high frequency state, the eddy current loss alone accounts for 40%-70% of the total loss, so this requires silicon steel to have as low a high frequency iron loss as possible, which can improve the efficiency of the motor and increase the cruising range of new energy vehicles , It can also suppress the temperature rise and avoid the demagnetization of the permanent magnet; during the vehicle start and low-speed climbing stages, the motor needs to output a huge torque enough to drive the car to start, so it needs to have as high a magnetic induction as possible. In addition, the huge centrifugal force during high-speed operation and the strict design of the stator-rotor clearance also require the rotor material to have a higher yield strength. Therefore, new energy vehicle drive motors with high speed and high power density require the use of cold-rolled non-oriented silicon steel sheets with thinner specifications (≤0.35mm), lower high-frequency iron loss, higher magnetic induction, and high yield strength.

Due to the long process flow, narrow process window and difficult production of high-strength non-oriented silicon steel products for new energy vehicle drive motors, there are few enterprises with large-scale and stable production capacity in the world. At present, non-oriented silicon steel for new energy vehicle drive motors can be produced by Japanese JFE, Nippon Steel, and South Korea’s Posco in the world, while only a few companies in China, such as Baosteel, Shougang, and Taiyuan Iron and Steel, can mass-produce. With the rapid development of new energy vehicles, the global market demand for non-oriented silicon steel for drive motors of new energy vehicles is strong.

We cooperate with Baosteel to provide high quality non-oriented silicon steel, contact us for more information about non-oriented electrical steel.