Journal of Magnetism and Magnetic Materials 215}216 (2000) 690 } 692 Aspects of the cut-edge e!ect stress on the power loss and #ux density distribution in electrical steel sheets A.J. Moses*, N. Derebasi, G. Loisos, A. Schoppa School of Engineering, Cardiw University, P.O. Box 687, Cardiw CF2 3TD, UK EBG Electroblech Bochum GmbH, Castroper-Str 228 Bochum, Germany Abstract This paper describes some e!ects of cutting on power loss, localised #ux distribution and B}H curves of a fully processed, high permeability non-oriented electrical steel. Cutting a single sheet into narrow strips increased the power loss by up to 30% and signi"cantly changed the B}H characteristics. The change in #ux distribution caused by cutting was lower when magnetised at 400 Hz than at 50 Hz.  2000 Elsevier Science B.V. All rights reserved. Keywords: Mechanical stress; Magnetic properties; Non-oriented steel A mechanical strain caused by shearing stresses, occur- ring during the process of cutting electrical steel sheets, will cause deterioration of the magnetic characteristics of the sheet. One result is that, when magnetised parallel to the cut edge of a sheet the magnetic #ux density mea- sured in the cut-edge region is less than the #ux density at the centre of the sample. The deterioration of magnetic properties can be deduced from a study of the change in the #ux density distribution before and after cutting. There is con#icting evidence of the quanti"cation of the e!ect of cutting stress on the #ux distribution and loss in non-oriented electrical steel laminations. Early work by Carlberg [1] suggested that a 1 mm wide degraded area could be expected adjacent to a sheared edge of an electrical steel strip. Schmidt [2] measured loss and per- meability in 1% SiFe and identi"ed a cut-edge hardening region 0.35 mm wide. Increases of loss of 30 to 40% in a strip of &speci"c cutting length' 100 m/kg (length of the cut-edge per unit mass of the sample) were found. The corresponding induction drop was 70%. Nakata et al. [3] has indicated that the degradation of magnetic pro- perties of non-oriented silicon steel sheet due to cutting extends as far as 10 mm from the cut, the deterioration being particularly pronounced up to 5 mm from the edge. * Corresponding author. Fax: #02920-874735. E-mail address: mosesaj@cj.ac.uk (A.J. Moses). In this work, non-oriented electrical steel sheets 300 mm100 mm were magnetised in a single-sheet tes- ter. Specimens designated as 400-50 AP (typically 3.7 W/ kg at 1.5 T}50 Hz) were successively cut into two strips (250 mm), four strips (425 mm) and "nally eight strips (812.5 mm). The 0.48 mm thick samples were cut under controlled conditions using a power guillotine. After each cutting process the groups of 2, 4, or 8 strips (total width 100 mm) were tested in the system shown in Fig. 1. The single-sheet tester (SST) comprises the strip(s), magnetising and secondary windings and U-shaped #ux return yoke. The voltage induced in a 10-turn coil wound around the 100 mm was used for monitoring and maintaining sinusoidal #ux density. Localised #ux density, power loss, and magnetic "eld strength were measured over the peak #ux density ranges 0.2}1.5 T at 50 Hz and 0.2}0.9 T at 400 Hz. Two-turn localised search coils, wound from 0.15 mm diameter enamelled copper wire were threaded through 0.3 mm diameter holes drilled through the sample in a manner to minimise stress to within one diameter distance from each hole [4]. The voltage across the shunt resistor (proportional to H) and the induced voltage in the 10-turn search coil (proportional to dB/dt) were fed to an electronic power analyser to measure the power loss. The shunt current method was also used for magnetic "eld measurements. The average voltages in- duced in local search coils (Fig. 2) were measured to analyse the #ux density changes due to cutting. The 0304-8853/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 8 8 5 3 ( 0 0 ) 0 0 2 6 0 - 2