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Legal regulations applicable to industrial motors or the desired extension of the range of electric vehicles with existing battery capacity require increased efficiency in electric machines. A precondition for this is the use of low-loss electrical steels combined with high magnetic permeabilities.
The behavior of the electric motor is additionally influenced by the respective bonding process. Experience has shown that face bonding is the most gentle and versatile bonding method.
Face bonding leads to the best-possible performance and a high degree of motor efficiency for the following reasons:
Self-bonding varnish allows versatile motor engineering because manufacturing aspects such as the positions for interlocking or weld seams do not have to be taken into account. This makes it possible to engineer a more efficient electric motor.
Face bonding allows for the maintenance of narrow dimensional tolerances and excellent dimensional stability since the individual laminations are not only connected at discrete points but also utilize the surface bonding connection between the laminations.
In comparison to punch stacking and welding, the bonding process is the most gentle bonding method because it does not alter the microstructure either through mechanical deformation (punch stacking) or temperature input (welding). This means that magnetic properties are not significantly affected.
There is no air gap between laminations when they are face-bonded. This means that thermal conductivity in the axial direction is improved when compared with stacks that feature an air gap. (See schematic diagram.)
Face bonding minimizes the vibration between individual laminations, and this has a direct effect on the acoustic behavior of the component because noise is reduced in the respective electric machine.
Filling the areas between the laminations with bonding varnish not only increases thermal conductivity of the stack. The stacking factor is also reduced considerably less than would be expected from the higher layer thickness of the bonding varnish.
Schematic representation of thermal conductivity:
