IEC TR 63304-2021 pdf free download – Methods of measurement of the magnetic properties of permanent magnet (magnetically hard) materials in an open magnetic circuit using a superconducting magnet.
The magnetic dipole moment of the test specimen is detected by the voltage induced in the M coil due to the movement of the test specimen (see 4.4).The magnetic polarization of the test specimen is calculated from the magnetic dipole moment and the volume of the test specimen(see 7.2).For calibration aspects, see Clause 9.
There are two methods different in modes of the movement of the test specimen:
a) the SCM-vSM method: the test specimen is vibrated with a small amplitude in theM coil;b) the SCM-Extraction method: the test specimen is extracted through theM coil.
NOTE There is another method to determine the magnetic polarization of the test specimen,ie. the SCM-Magnetometer method. In this method,variation of the magnetic polarization of the stationary test specimen due tovariation of the magnetic field strength applied to the stationary test specimen is detected by the voltage induced inthe detection coil ( coily (see Annex A).
The measurements are carried out at an ambient temperature of (23±5)°C. For permanentmagnet materials which are known to have significant temperature coefficients a(Jr) and a(HcJ),the temperature of the test specimen should be in a range between 19 °C and 27 ℃ andcontrolled within a tolerance of 1°C during the measurements in accordance with IEC 60404-5.
The temperature of the test specimen should be measured by a non-magnetic temperaturesensor.
The demagnetization curve measured in an open magnetic circuit is influenced strongly by theself-demagnetizing field in the test specimen which opposes magnetization.
In order to determine the intrinsic demagnetization curve of the permanent magnet material, a correction of the influence of the self-demagnetizing field (hereafter demagnetizing fieldcorrection)should be applied to the measured demagnetization curve (see Clause 11).Magnetic properties of the permanent magnet material are determined from the correcteddemagnetization curve.
These two methods have the following features:
1) The most important feature is that it is possible to determine all the magnetic properties of permanent magnet materials with coercivityhigher than 2 MA/m in contrast to the methodof measurement in a closed magnetic circuit in accordance with lEC60404-5.
2) The reproducibility of measurement by the methods is comparable with that of lEC 60404-5.lt was confirmed by the international round robin test (see Annex F).
3) The influence of eddy currents in the test specimen is negligible.
4) By adopting the ceramic sCM made of ceramic high temperature superconducting coil,demagnetization curve can be measured within several minutes without using expensiveliquid helium and its incidental facilities (see Annex C). Also test apparatus using theceramic SCM which can deal test specimens of industrial size has been commercialized for industrial use.So, it is convenient for industrial use globally.
5) There is no drift in the signal of the magnetic dipole moment, owing to the use of a phase sensing device (lock-in amplifier) in the SCM-vSM.
4.2Superconducting magnet (ScM)
A variable DC source supplies a DC current to the superconducting coil,with sufficiently lowvoltage noise (see Figure 2). The current source should be a bipolar type which can switchpositive-negative polarity continuously.
The SCM is recommended to have a capacity to generate a magnetic field strength more than 4,8 MA/m (6T in magnetic flux density) in order to measure the magnetic properties ofpermanent magnet materials with coercivity higher than 2 MA/m, e.g.Nd-Fe-B sintered magnets.IEC TR 63304 pdf download.