Measurements of Iron Loss in PMSM Stator Cores Based on CoFe and SiFe Lamination Sheets and Stemmed From Different Manufacturing Processes

Abstract

This paper deals with the experimental study of the iron losses under real operating conditions of a permanent magnet synchronous machine. The latter is a high frequency (>1 kHz) and high power-to-weight ratio (4 kW/kg) motor intended for an aerospace application. The measurements were carried out on different laminated stator cores based on classical commercial grades, namely, the NO20 and M270-35A for the silicon–iron alloy and the Vacodur49 (0.2 mm) for the cobalt–iron alloy. The lamination sheets stemmed from different manufacturing processes: insulation (bonding varnish and C5 varnish), cutting (laser and electrical discharge machining), and thermal treatment (fully processed only and fully processed + thermal re-treatment after cutting). We measured the iron losses at no load and over a wide range of frequency (speed) until around 1400 Hz, and then we compared them to the estimations yielded by the finite-element model under ANSYS Maxwell. Hence, this allowed us to accurately assess the iron loss add-on factor ( $K_{\mathrm {add}}$ ), which takes into account the extra magnetic loss caused by a complex magneto-thermo-mechanical coupling within the ferromagnetic material. This coupling occurs during the manufacturing and the assembly phase (cutting, welding, stacking, shrink fitting, …) and also during the real running conditions of an electrical machine (elliptic field, local saturation, high frequency, and harmonics).