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Soft Magnetic Composites in Electrical Motors

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How to mitigate shortage of electrical steel
Reduce weight of your motor, save money and mitigate the potential shortage on copper wire
Optimize motor design with software simulation

New possibilities

The 3-dimensional magnetic properties of SMC result in completely new possibilities compared to traditional laminated sheet metal, which only has good properties in 2 directions (and in transformer sheet metal only 1 direction).

By exploiting these 3D properties, the compo­nent design can often be made smaller, lighter and more economic, and as such integration with the surrounding system also becomes easier as the number of geometric limitations is reduced. The complicated 3D geometry and alternative flux paths enable a high fill factor for both iron and copper windings.

Compared with laminated sheet metal, SMC components can be manufactured very efficiently in a single opera­tion without a complicated manual handling process. The design of SMC is therefore not limited in the same way as laminated sheet metal, and the powder process is a well-established and highly suitable process for mass production. The result is efficient manufacturing of com­ponents at low cost, which means that the price of the end product can be on par with other solutions

Properties compared to laminated sheet metal

B-H curve: SMC materials are isotropic 3D core materi­als with a maximum relative permeability in the range 100-700, which means that the material is 100-700 times better at conducting magnetic flux than air. Generally speaking, this figure is lower than for laminated sheet metal, but in practice this is of minor significance since the major part of the magnetic potential drop lies across the air gap.

Resistivity: The isotropic 3D resistivity lies in the range 20-10,000μΩm, which is considerably higher than lami­nated sheet metal, which is around 0.2μΩm. SMC compo­nents therefore do not need to be laminated to minimize eddy current loss.

Iron loss: Iron loss occurs as a result of the material’s resistance to being magnetized (hysteresis loss) and as a result of electrical currents which counteract changes in the magnetic field in the material (eddy current loss).

The graph below shows the iron loss as a function of frequency for 2 selected material types and laminated sheet metal.

Reduced stator bridge – optimized design using the 3D potential

A normal stator is build on 3 fundamental elements. A Yoke, The stator teeth and the bridge connecting the yoke and the teeth. When building a stator with laminated sheets, the yoke, the teeth and the bridge are make in thin plates stacked on top of each other resulting in a two-dimensional component.

When building such a stator in Soft Magnetic Composites there is a new degree of freedom enabling us to reduce the height of the bridge within the frames of the calculated saturation of the iron. By doing this the amount of copper can be significantly reduced as well as the height of the stator as the end windings are now placed in the undercut within the total stator height. A demonstrator of this is shown on the picture below, where Jan exhibits the size different of stators made on laminated sheets compared to SMC material.

We have seen several examples of a copper reduction around 30% which means a lot both of motor efficiency as well as on the weight of the motor.

But in some applications low weight is more essential than efficiency. This could be the case for smaller motors in automotive where running time is few minutes per day, but weight load is 100%. These motors could be strongly reduced in weight if the optimum combination of SMC stator design combined with the substitution of copper with aluminium wire could be implemented. Please feel free to contact our motor experts in order to learn how much weight your motor could safe when changing to a new Sintex design.

You can also learn more in our case story here.

Split stator – reaching extremely high fill factor

When designing electrical motors one of the limiting factors is the copper fill factor in the stator. It can be very easy to design and simulate the motor with a high filling factor, but on the other hand it can be extremely difficult to place the copper in the slots and also have space for the needle between the stator teeth and the stator bridges.

At Sintex we have developed a new solution to ensure a high filling factor enabling us to manufacture motors with high very power density.

Recycling by crushing and separation

When developing future products it is important to ensure that the raw materials can be separated and recycled in order to reduce the impact on our environment as well as to build up an urban mining system with a sustainable economy. One of the tools to decide for one solution over another is Life Cycle Analysis (LCA). It is known that separation of the laminated stator iron from the copper windings can be difficult or costly in man power. Therefore it is often seen that the entire motor is recycled as steel scrap resulting in copper pollution of the steel and the need to add virgin iron material to dilute the copper.

When designing a motor based on SMC separation of the copper from the stator can be done by a simple crushing machine ensuring a 100% recycling of the scarce copper material. Sintex has been collaborating with a local university on LCA and can help our customers with the optimized design towards a low LCA impact of their electrical motors.

Video Podcast

View our full episode on our video podcast regarding Soft Magnetic Composites. An interesting discussion between Peter Kjeldsteen and two researchers from the University of Pisa.

Recent

Case studies

  • Stator design with SMC

    Stator design with SMC

    Stator design is one of the interesting applications for SMC. With the right design, one could potentially make a cheaper, smaller and more efficient motor…

    Read more

    Stator design with SMC

    Stator design is one of the interesting applications for SMC. With the right design, one could potentially make a cheaper, smaller and more efficient motor…When using SMC for a stator, it is important to utilize its unique geometrical possibilities in order to get the desired benefits. Replacing a stator in laminated steel with an identical one in SMC will rarely be beneficial, as the price is roughly the same, but the SMC will have a slightly higher degree of iron loss.

    Instead, it is preferable to shape SMC in all three dimensions, which is not possible with laminates. In the following example, a comparison between a stator made in 0.5 mm laminated iron and STX B7X SMC is made. The stator design is similar except the tooth length has been shortened and rounded as can be seen on the above drawing.

    Basic motor specification:

    • Stator outer diameter: 80 mm
    • Stator length: 20 mm
    • Stator teeth: 6
    • Rotor outer diameter: 28 mm
    • Ferrit-Rotor
    • Poles: 4

    Loss

    By utilizing the optimized shape, it is possible to use less copper while maintaining the same number of windings.

    If we look at the diagram, it is evident that the iron loss will be higher for SMC compared to laminated iron, but the copper loss is significantly lower when using the optimized SMC shape. The outcome is a lower combined iron and copper loss resulting in a more efficient motor.

    Copper cost

    Decreasing the length of the copper winding also has a cost saving aspect.

    The total copper weight of the stator:

    • Laminated tin: 172.5 g
    • SMC material: 115.8 g

    In this case the copper weight is reduced by more than 30%, thereby lowering the material cost.

    Size

    Due to the optimised shape, the end windings will protrude less beyond the stator with SMC (left) compared to laminated core (right) which makes it possible to decrease the volume of the entire motor.

    All simulations have been done using SPEED PC-FEA.

    With the right design, one could potentially benefit from…
    • a cheaper solution
    • a smaller motor
    • a more efficient motor

    … and not least a technological boost to your products, which can also have an impact on the bottom line!

     

    Products

    Contact sales

    Jan Graff
    Commercial Director

    +45 4020 4199
    jagr@sintex.com

    Sintex

    Information

    Datasheets

    • STX S7 SMC

      STX S7 SMC is a soft magnetic material that is characterized a strong material with a 3-point shear strength at 125 MPa.

    • STX S7B SMC

      STX S7B SMC is a soft magnetic material that is characterized a strong material with a 3-point shear strength at 120 MPa.

    • STX S10 SMC

      STX S10 SMC is a soft magnetic material that is characterized a strong material with a 3-point shear strength at 140 MPa.

    • STX M7 SMC

      STX M7 SMC is a soft magnetic material that is characterized by its overall good properties and is suitable for stators in electrical motors.

    • STX B7 SMC

      STX B7 SMC is a soft magnetic material that is characterized by its overall good properties for big components with large wall-thickness.

    • STX B7X SMC

      STX B7X SMC is a soft magnetic material that is characterized by very low losses under 1 kHz.

    • STX H3 SMC

      STX H3 SMC is a soft magnetic material that is characterized by good permeability and it is especially designed for higher frequency use (typically above 2kHz).

    • STX H1 SMC

      STX H1 SMC is a soft magnetic material that is characterized by good permeability and it is especially designed for high frequency use (typically above 4kHz).

    • STX SMC PROTOTYPING MATERIAL

      Sintex develops and manufactures customised components in various different Soft Magnetic Composites (SMC). The choice of SMC material depends on many factors. We can help you evaluate your wishes and requirements, so that you choose the correct choice of material.

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