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INTERCOMPARISON OF MEASUREMENTS OF PERMANENT MAGNETS

Objective



The intercomparison covers the determination of :

- remanent induction Br;
- coercivities HcB and HcJ;
- maximum energy product (HB)max.

NdFeB and AlNiCo8 have been selected because of their properties and technological importance.

Two classes of measuring techniques will be used by the participants. The first and most widely used employs a closed circuit apparatus, in which cylindrical samples are placed in between the poles of an electromagnet. In the second, approximately 3 mm diameter spheres will be held in the field of an open circuit apparatus, such as vibrating magnetometers. This latter intercomparison will be limited to NdFeB, because, in this configuration, the high remanence and low coercivity of AlNiCo8 make it difficult to correct for demagnetizing effects.

As accurate calibration is an essential prerequisite for the success of the intercomparison, reference samples will be distributed to all participants.

RESULTS

Besides AlNiCO and NdFeB specimens, Ni reference specimens were also circulated for calibration purposes. The results of the audits are complex, but in general it can be said that the agreement obtained has been quite good within the two separate groups (cylinders and spheres). The correlation between the results of the two separate methods turned out to be unsatisfactory in so far as the small spherical specimens had changed their properties as a results of the preparation process.

Coordinator

Univers. Ingeniera Tecnica Industrial

Participants (21)

AACHEN UNIVERSITY OF TECHNOLOGY
Germany
Address
Templergraben 55
52056 Aachen
Centro Magneti Permanenti SpA
Italy
Address
Via Iv Novembre 489
20123 Caronno Pertusella
Industrie Ossidi Sinterizzati SpA
Italy
Address
Viale Dell'industria 23
21023 Malgesso Varese
Instituto de Ciencia de Materiales de Aragon
Spain
Address

Zaragoza
Istituto Maspec Parma
Italy
Address
Via Chiavari 16/C
43100 Parma
Krupp Widia GmbH
Germany
Address
Münchener Straße 90
45145 Essen
Laboratoire d'Electrotech. Grenoble
France
Address

Grenoble
Magnet-Physik Dr. Steingroever GmbH
Germany
National Physical Laboratory (NPL)
United Kingdom
Address
Queen's Road
TW11 0LW Teddington
PHYSIKALISCH-TECHNISCHE BUNDESANSTALT
Germany
Address
Bundesallee 100
Braunschweig
Philips Components
Netherlands
Philips Components
United Kingdom
Address

SO Southampton
Siemens AG
Germany
Swift Levick Magnets Ltd
United Kingdom
Technical Univers. of Danemark
Denmark
Thyssen Edelstahlwerke AG
Germany
Address
Auestraße 4
58542 Witten
Ugimag Recoma AG
Switzerland
Univers. Porto
Portugal
Univers. of Dublin
Ireland
University of Sunderland
United Kingdom
Address

Sunderland
VACUUMSCHMELZE GMBH
Germany
Address
Gruener Weg 37
63450 Hanau