Rotor / stator stacks enable up to 50% more torque for electric motors

June 03, 2013 // By Christoph Hammerschmidt
Smaller, more powerful electric motors are one of the most important design goals of power trains in future electric vehicles. Materials expert company Vacuumschmelze GmbH (VAC) has developed several iron-cobalt alloys that enable designers to increase the torque of their motors by 20 to 50% at the same size. Besides the improvements in materials properties, VAC also succeeded in creating rotor and stator packet blades as thin as 0.05 mm - this allows motor designers to eliminate 99% of the eddy current losses generated with usual blades of 0.5mm.

VAC's alloys are used in permanently excited electric motors in the first place. As an example, the AMZ racing team of the ETH Zurich university utilizes these materials and rotor / stator blades in the motor of its Formula Student Electric vehicle. Using the 0.1mm Vacoflux 48 blades, the motor generates a power of 35 kW and a torque of 32 Nm - despite its remarkable low weight of just 5 kg.

Another VAC customer is Brusa Elektronik AG, a Swiss company dedicated to electric powertrains for hybrid and all-electric vehicles. Brusa recently achieved designing a motor which delivers 187 kW and a rather interesting torque of almost 500 Nm. With a weight of just 54 kg, this motor could be an ideal candidate for high-power racing cars. These performance parameters have been achieved by the use of Vacodur 50 rotor and stator blades from VAC.

Compared to conventional iron materials such as M270-35A, iron-cobalt alloys allow significantly higher saturation polarization values. Vacuumschmelze products such as Vacoflux 48 and Vacoflux 50 as well as the new Vacodur 50 offer a magnetic flux density of 2.35T - a top value among all known magnetically soft materials. This enables the design of electric motors with very high power density.

At the Coil Winding trade fair which in Berlin from June 4 to June 6, VAC will exhibit these materials. Also new in VAC's display (booth number 2413) are stator / rotor blade stacks made of 50 micron metal tape.

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