Effect of Different Cutting Techniques on Magnetic Properties of Grain Oriented Steel Sheets and Axial Flux Machines

Various cutting techniques are in use as part of the manufacturing process of electrical machines such as laser cutting, punching, electrical discharge machining and waterjet cutting. The cutting process degrades the magnetic material near the cut-edge. This degradation results in lower magnetic permeability and higher core-loss density. This paper studies the effect of three different cutting techniques namely punching, waterjet and laser cutting on the magnetic properties of the grain oriented electrical steel sheets. A standard Epstein test confirms the different magnitude of degradation depending on the cutting technique. Further, a loss model based on the measurement results has been applied to the yokeless axial flux machine. The comparative analysis shows the superiority of the punching and water-jet cutting techniques over laser cutting which resulted in more than 150% increase in the core losses. Other machine performance parameters such as generated EMF and torque remain unaffected by the cutting method.