AC Magnetic Loss Reduction of SLM Processed Fe-Si for Additive Manufacturing of Electrical Machines

Abstract

Additively manufactured soft magnetic Fe-3.7%w.t.Si toroidal samples with solid and novel partitioned cross-sectional geometries are characterized through magnetic measurements. This study focuses on the effect of air gaps and annealing temperature on AC core losses at the 50 Hz frequency. In addition, DC electromagnetic material properties are presented, showing comparable results to conventional and other 3D-printed, high-grade, soft magnetic materials. The magnetization of 1.5 T was achieved at 1800 A/m, exhibiting a maximum relative permeability of 28,900 and hysteresis losses of 0.61 (1 T) and 1.7 (1.5 T) W/kg. A clear trend of total core loss reduction at 50 Hz was observed in relation to the segregation of the specimen cross-sectional topology. The lowest 50 Hz total core losses were measured for the toroidal specimen with four internal air gaps annealed at 1200 °C, exhibiting a total core loss of 1.2 (1 T) and 5.5 (1.5 T) W/kg. This is equal to an 860% total core loss reduction at 1 T and a 510% loss reduction at 1.5 T magnetization compared to solid bulk-printed material. Based on the findings, the advantages and disadvantages of printed air-gapped material internal structures are discussed in detail.

Additive Manufacturing and Performance of E-Type Transformer Core

“…Transformer parts were printed with identical powder, processing, and annealing parameters to the previous study characterizing the AC and DC losses of the printed material [6]. Pre-alloyed, gas-atomized Fe-Si provided by Sandvik group was utilized for printing.…”

“…The additively manufactured 3.7% silicon steel shows comparable magnetic performance to non-oriented conventional silicon steels after thermal treatment. Magnetization of 1.5 T is achieved at 1800 A/m, exhibiting electrical resistivity of 56.9 µΩ•cm and hysteresis losses of 0.61 (W 10,50 ) and 1.7 (W 15,50 ) W/kg [6]. In comparison, a typical non-oriented steel M235-35A used for electrical machine fabrication exhibits total core losses of 0.92 (W 10,50 ) and 2.35 W/kg (W 16,50 ), resistivity of 59 µΩ•cm, and magnetization of 1.53 T at 2500 A/m.…”

“…The grain-oriented transformer steel shows approximately 0.3 T greater saturation magnetization than both of the non-oriented steels. [10,11], non-oriented silicon steel M235-35A [12], printed annealed 3.7% silicon steel, and printed unannealed 3.7% silicon steel [6].…”

“…State of the art additive manufacturing of electromagnetic devices involves selective laser melting (SLM) printing of conductive and soft magnetic materials with air gaps State of the art additive manufacturing of electromagnetic devices involves selective laser melting (SLM) printing of conductive and soft magnetic materials with air gaps partitioning the material structure for separating individual turns in coils and reducing the induced eddy currents in soft magnetic cores [5,6]. The air gaps are printed due to the current lack of multi-material printing capacity of SLM systems, limiting the parallel printing of conductive, core, and insulation materials.…”

“…The air gaps are printed due to the current lack of multi-material printing capacity of SLM systems, limiting the parallel printing of conductive, core, and insulation materials. The introduction of airgaps considerably reduces the power density of the components, however, as gapped printed component fill factor is typically relatively low (in the range of 60%) [6,7].…”