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 cupper 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 cupper 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.
Split stator – reaching extremely high fill factor
When designing electrical motors one of the limiting factors is the cupper 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 cupper 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 cupper 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 cupper pollution of the steel and the need to add virgin iron material to dilute the cupper.
When designing a motor based on SMC separation of the cupper from the stator can be done by a simple crushing machine ensuring a 100% recycling of the scarce cupper 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.
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.
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…
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
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.
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.
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 motors
… and not least a technological boost to your products, which can also have an impact on the bottom line!
Powder metallurgy is recognized as green technology, and at Sintex, we aim to advance processes within several areas – not only to ensure a sustainable technology, but also to streamline and optimize our solutions for high-volume production. Click here to read more.