No-Load Loss Distribution of High-Power Induction Machines with Magnetic Slot Wedges

This paper addresses the need for a precise assessment of the impact of magnetic slot wedges on no-load loss distribution by developing a localized loss calculation model based on Finite Element Analysis. The developed model demonstrated accurate prediction in quantifying losses, as validated through experimental results. Experimental validation utilized a grid-supplied, 1250 kW, 690 V, 6-pole squirrel cage induction motor by measuring total no-load losses before and after the insertion of magnetic slot wedges. Applying magnetic slot wedges significantly reduces rotor loss components, primarily in the cage winding and iron core. In contrast, the stator's magnetic core exhibited a less pronounced loss reduction. The main results of this research show that the specific construction of low-voltage and high-power induction machines can lead to unexpected increases in commonly negligible no-load rotor losses, mainly when magnetic slot wedges are not applied. Only through the developed local loss model is a comprehensive evaluation of the benefits of magnetic slot wedges achieved, highlighting their role in optimizing overall loss distribution within high-power induction machines.