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Thin, Lightweight, Strong: Armor Sleeves for Electrical Motors

The efficient and economical alternative to commutator motors

CFRP Sleeves for Electrical Motors


More information:

Our fiber reinforced armor sleeves for permanent magnet motors are used in modern motor systems to fasten and secure rotating assemblies, enabling eddy current loss to be minimized.

High-performance electrical motors pose enormous challenges for manufacturers. Materials made of carbon-fiber reinforced plastics, so-called CFRPs, are an important approach for achieving long-lasting and highly efficient motors. Volker Bier explains what solutions Schunk offers for advancing the development of electrical mobility. He is the Senior Manager for New Business & Technology at Schunk Carbon Technology.


Mr. Bier, numerous industries are counting on a boom in the field of electrical mobility. This, however, will closely depend on electrical motors becoming more efficient. What are the challenges we face here?  

Volker Bier: At rotational speeds of up to 100,000 revolutions per minute, extreme centrifugal forces are exerted on the parts used in an assembly. Here, lightweight and dimensionally stable materials present a cost-efficient alternative. For this reason, we offer carbon and glass-fiber reinforced armor sleeves which, despite having a thin-walled construction, retain their dimensions and can increase the efficiencies of motors. They make a more compact design possible.

Automotive engineering was not the first field in which you were confronted with these requirements, correct?

Volker Bier: Yes, that’s right. The basis for all the products are the developments from the last 40 years. An important precursor for today’s solutions were the carbon-fiber reinforced polymer sleeves for the pump industry: the thin-walled and lightweight components significantly increased the efficiency of turbo molecular pumps. These experiences led us to focusing on lightweight solutions for electrical motors since the beginning of the millennium. An example for this is the CFRP flywheel for the KERS system, the system for the recovery of kinetic energy in Formula 1 race cars. At the time, that was a genuine innovation in the automotive industry. So, we have a lot of experience in this field, and we like to use it in service to our customers.

But it’s not all just about lightweight design. What exactly is the advantage of CFRP armor sleeves?

Volker Bier: We have always combined lightweight design with a technologically demanding value-adding function. Our carbon-fiber reinforced sleeves as well as our glass-fiber reinforced sleeves are used for fastening and securing magnets in high-performance electrical motors. Compared with ordinary high-grade steel sleeves for fastening magnets, our fiber-reinforced parts are many times lighter yet nevertheless stronger.  Furthermore, designs are feasible with a wall thickness of considerably less than 1 mm. Thanks to their thin jacket, a compact design with a particularly small air gap between the stator and rotor is possible. This reliably prevents contact between the magnets and the stator, which would otherwise lead to heavy damage to the material. Our reinforcement sleeves retain their shapes in electric motors, even at very high temperatures. This allows electrical motors to withstand higher temperatures and rotational speeds.  

Are there applications for CFRP sleeves aside from electrical mobility in the automotive industry?

You bet! The sleeves are manufactured very precisely. Their accuracy of fit differs depending on the application. Manufacturers of other products which contain motors also benefit from this property. These applications include vacuum cleaners, power gardening tools, power drills, and many other power tools. We are working together with our customers on projects for individually adapting the assembly of sleeves and rotors. They all profit from the fact that carbon and glass-fiber reinforced sleeves perfectly fasten the drive magnet in high-performance electrical motors.    


Interested? Click here to learn more about our innovative CRFP sleeves!

View now: CFRP Sleeves for Electrical Motors


More information:

Our fiber reinforced armor sleeves for permanent magnet motors are used in modern motor systems to fasten and secure rotating assemblies, enabling eddy current loss to be minimized.

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Your contact person for this article is:

Volker Bier

Senior New Business Manager

Tel.: +49 (0)641 608 2330

Rodheimer Straße 59
35452 Heuchelheim

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