Electric & Hybrid Vehicle Technology - July 2021
EV motor performance (Carpenter Electrification)
2021-07-21 03:46:49
The next generation of torque-dense electric motors will be driven by high-induction soft magnetic materials and new lamination and stacks technology
Enhanced power and torque densities are critical for high-performance electric motors and generators. EV designers must carefully consider size and weight constraints for their impact on operation. Recent advancements in electrification sectors such as electric vehicles, aircraft, drones, robots, and other size and weight sensitive applications further highlight the need for improved system performance.
The emergence of WBG power electronics such as silicon carbide (SiC) and gallium nitiride (GaN) is expanding the options for powertrain designs. New motor drives using these technologies are extremely efficient at high frequencies, enabling significantly higher power density. However, the higher switching frequencies can have a negative effect upon stator and rotor performance. These effects can be mitigated through the selection of optimal material and stack construction.
For high-speed motor applications, thinner, soft magnetic laminations in stator and rotor stacks help achieve higher continuous motor power because lamination materials exhibit lower core losses due to lower eddy current contributions. As motor speed increases, it becomes critical to choose the best combination of alloy and lamination thicknesses to keep iron losses low and achieve the highest possible continuous power density, along with high torque responses.
As highlighted, choosing the optimal material selection is the key first step. Hiperco has the highest magnetic saturation (24 kilogauss) of any commercially available soft magnetic alloy. In addition to the high induction, it has high permeability and low core losses.
Using Hiperco-based motor stacks has been shown to increase motor performance by reducing motor size while increasing power and running cooler — up to 25% higher torque, 30% power density increase, and 3% greater efficiency when it is implemented as a drop-in solution in current motor designs.
Once the optimal material is determined, EV motor designers must then consider optimal thickness. Most alloys are available in a selection of standard thicknesses to support various frequencies, and thicknesses can be customized for specific applications.
As operational frequency increases, thinner laminations become more effective due to the decrease in eddy current contributions, even though the hysteresis losses increase.
The magnetic and mechanical properties of alloys such as Hiperco can be modified by varying process parameters to improve core loss behavior. Through expert processing, the range of optimal operational frequency for a lamination thickness can be modified. This is particularly important, as using the right lamination thickness must be carried out carefully so that both performance and overall cost are taken under consideration.
The optimal approach and material properties are a function of the motor design and application. These choices are particularly critical for motors operating at high frequencies. Partnering with a soft magnetics alloy expert that can help with defining mechanical and magnetic properties, lamination thickness, and stack processing is critical to ensures that cutting-edge EV motor designs live up to their potential on the road, in the air, and on the job.
Carpenter Electrification has been providing soft magnetic motor solutions for more than 50 years. From tooling and stamping to annealing, insulation, bonding, and quality testing, Carpenter Electrification offers a simplified supply chain and short lead times for prototypes and mass production of high-performance motors.
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To learn more about Carpenter Electrification, visit: www.magupdate.co.uk/PEHV
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