High frequency behaviour of laminated magnetic structures

Electrical stress on winding insulation of AC machines fed by modern PWM inverters becomes more and more important as switching speed of power electronic devices increases because local resonances, due to parasitic capacitors, may occur. This paper studies the laminated iron structure behaviour in order to detect these local resonances by measuring magnetic field around the machine. First of all, a simple analytical model is proposed and verified with an elementary strip-wound cut core, then field measurements near a laminated magnetic structure show the weakening of its shielding effect when frequency increases