Numerical modeling of energy efficient electrical machines requires accurate and fast calculation of losses. One such loss component is core losses related to magnetic material degradation due to cutting of electrical sheets. This paper analyzes the application of higher order finite elements for precise and computationally efficient modeling of these cutting related losses.

Cutting of the electrical steel sheets to appropriate shape and size is performed during the manufacturing of electrical machines which leads to the magnetic material deterioration near the cutting edge. Epstein frame measurements of electrical steel samples of different widths cut by laser cutting are carried out in the range of 20 Hz to 400 Hz frequency of sinusoidal excitations. Two stators one with laser cut and another one with electric discharge wire cutting were manufactured and the effect of cutting on core losses was analyzed. The effect of cutting on the magnetic permeability and core losses are modeled with analytical equations. Furthermore, the model is implemented in the finite element simulation of the Epstein frame test setup. The presented loss model is found to reproduce the measurement results reasonably. The loss model is then applied to the simulation of a cage induction machine with time-stepping finite element analysis. A significant increase in core losses was observed both in simulations and measurements due to the effect of laser cutting. The presented cutting model closely follows the measured core losses.

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Cutting the electrical steel sheets to form the shape of the stator and the rotor affects the magnetic properties of the sheets. The increase of the magnetic losses as well as the drop of the magnetic permeability can impact on the design of electrical devices. This paper investigates this deterioration effect on the optimal design of the stator of a high-speed permanent magnet synchronous motor. The deterioration due to punching is phenomenologically analyzed based on measurement of strips of steel sheets with various widths on an enlarged Epstein frame. The losses are computed with a Bertotti model whose coefficients depend on the width of the sheets. The optimization of a synchronous machine is then carried out with this magnetic losses model.

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