Iron loss modelling which includes the impact of punching, applied to high-efficiency induction machines

Abstract

Within the market evolution towards higher efficiency machines, there is a need for more precise modelling tools, taking also higher frequency power supplies into account. This paper implements the effect of cut edge degradation, due to punching, on the local magnetization curve and local losses, aiming at improved calculation of magnetization current and machine iron losses. For an induction machine, defined by Leroy Somer and a high efficiency electrical steel, selected from ArcelorMittal's range, this study combines advanced material characterization with improved modelling techniques, and is validated by selected machine testing procedures. For the sake of clear loss separation a machine with slotless rotor was characterized at two conditions regarding speed and excitation. The loss model, including already the effect of rotational losses and higher harmonics, was enhanced with the punching effect, which led to a model accuracy of 86% at synchronous speed when compared to the measured losses. This study also led to further insights in local magnetization behaviour, to be used in further design optimization.

Mixed-Order Finite-Element Modeling of Magnetic Material Degradation Due to Cutting

“…These elements are especially beneficial when we have to model a specific phenomenon in certain part of the solution domain efficiently. The developed loss model related to cutting presents a high degree of variation in permeability near the cut edge, which is normally represented by parabolic or exponential functions [6], [7]. However, it is observed that the cutting effect is negligible after 5-10 mm distance from the cut-edge.…”

“…5a , 6a and, 7a. Further, it should be noted that in general 4-5 different material layers of 0.5 mm-1 mm width of first order elements are normally introduced near the cut-edge [4], [6], [7]. Therefore, the first order reference mesh presented here can be treated as a reasonable mesh to model the presented cutting effect.…”

“…Therefore the cut-edge dependent local functions in (5) and (6) The application of third order nodal triangular elements to model the cutting effect is also presented in detail in [11]. In a similar fashion, the stiffness matrix S in the magnetic vector potential based AV finite element formulation will be modified as presented in (7). The source vector is presented as f.…”

“…The effect of the magnetic material degradation in different parts of a machine such as the stator teeth and yoke was considered by building factors [8] or by different magnetization curves [3]. Among the finite element based loss models, the effect of degradation is either quantified by a single degraded material layer near the cut edge [9], [10] or by many such layers [6], [7]. Many degraded layers present a gradual progression of the magnetic material degradation near the cut edge, which is Manuscript received September X, 2017; revised January X, 2018.…”

“…To include this degradation phenomenon in the electrical machine design process various authors developed associated loss models. Researchers have presented analytical loss models [5] as well as finite element based loss models [3], [6], [7]. The effect of the magnetic material degradation in different parts of a machine such as the stator teeth and yoke was considered by building factors [8] or by different magnetization curves [3].…”