Standards Development

Scope

The purpose of this part of IEC 60404 is to define the general principle and technical details of the methods of measurement of the steady state magnetic properties of permanent magnet materials in an open magnetic circuit using a Pulsed Field Magnetometer (PFM).

This method is applicable to permanent magnet materials, such as those specified in IEC 60404-8-1, the properties of which are presumed homogeneous throughout their volume.

This document also specifies methods to correct the influence of the demagnetising field in the test specimen on the demagnetisation curve obtained in an open magnetic circuit. The PFM rapidly measures the magnetic response of a test specimen in a pulsed magnetic field. Consequently, additional correction may be required to remove the influence of eddy currents generated in the test specimen. This document also specifies when such eddy current corrections should be applied. The magnetic properties are determined from a corrected demagnetisation curve.

NOTE 1 For the magnetic materials with coercivity higher than 1,6 MA/m, the methods of measurement in a closed magnetic circuit in accordance with IEC 60404-5 can lead to significant measurement error due to magnetic saturation in parts of the pole faces or the yoke (see IEC 60404-5). The PFM methods and methods contained in IEC 60404-18 are applicable to materials of any coercivity, including those with coercivities higher than 1,6 MA/m.

NOTE 2 There is another method of the measurement in an open magnetic circuit, using a superconducting magnet (SCM) which consists of SCM-vibrating sample magnetometer (VSM) method and the SCM-extraction method outlined in IEC 60404-18. Both these methods avoid the need for eddy current correction as the fields generated by the superconducting magnet used to measure the test specimen are sufficiently slow as to avoid eddy currents being generated.