Effect of Multilevel Inverter Supply on Core Losses in Magnetic Materials and Electrical Machines

Abstract

Abstract-The effect of multilevel inverter supply on power losses in magnetic cores and electrical machines is studied. A dynamic numerical model for the hysteresis, eddy current, and excess losses in a core lamination is first developed. By both measurements and simulations for a ring-core inductor, we demonstrate how increasing the number of inverter voltage levels decreases the iron losses when compared with traditional two-level supply. Although the switching frequency has a significant impact on the iron losses in the case of a traditional two-level inverter, using three or five voltage levels makes the losses almost independent of the switching. Finally, finite-element simulations show that similar reductions are also possible for the core losses of 150-kVA and 12.5-MW wound-field synchronous machines, in which rather low switching frequencies are typically used. Calorimetric loss measurements are also presented for the 150-kVA machine in order to confirm the significant effect of switching frequency on the core losses with two-level inverter supply.

Energy Management Strategy for Oscillating Drivetrains Equipped with an Electric Variable Transmission

“…Moreover, Fig. 5(b) shows the DC voltage variation with time which respects the constraint limit given by (11). It is obvious here that the voltage ripple is small, which means that very limited energy is stored in the capacitance at the DC-bus.…”

“…It is obvious here that the voltage ripple is small, which means that very limited energy is stored in the capacitance at the DC-bus. Also, lower voltage ripple results in lower inverter loss and the associated iron loss due to the change in the modulation of the pulse width of the inverter driver circuits [11].…”

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