IEC TR 63304:2021 pdf download

IEC TR 63304:2021 pdf download.Methods of measurement of the magnetic properties of permanent magnet (magnetically hard)
1 Scope
This Technical Report describes the general principle and technical details of the methods of measurement of the DC magnetic properties of permanent magnet materials in an open magnetic circuit using a superconducting magnet (SCM). 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. There are two methods: – the SCM-Vibrating Sample Magnetometer (VSM) method; – the SCM-Extraction method. This document also describes methods to correct the influence of the self-demagnetizing field in the test specimen on the demagnetization curve measured in an open magnetic circuit. The magnetic properties are determined from the corrected demagnetization curve. NOTE These SCM-methods can determine the magnetic properties of permanent magnet materials with coercivity higher than 2 MA/m. The methods of measurement in a closed magnetic circuit specified in IEC 60404-5 can lead to significant measurement error due to saturation effects in the pole pieces of yoke for the magnetic materials with coercivity higher than 1,6 MA/m (see IEC 60404-5).
4 General principle
4.1 Principle of the method Figure 2 illustrates schematic diagrams of typical test apparatuses. The test apparatus consists of a superconducting magnet (SCM), a moving device, a specimen rod, a magnetic field sensor (hereafter H sensor), a magnetic dipole moment detection coil (hereafter M coil), measuring devices and a data processing device (PC). The measurement is carried out in an open magnetic circuit to enable the determination of magnetic properties of permanent magnet materials with coercivity higher than 2 MA/m. The axis of the DC magnetic field generated by the SCM is vertical and coaxial with the M coil and the specimen rod. The moving test specimen is placed in a zone where the magnetic field strength is uniform with a tolerance of ±1 % at the centre of the SCM. The H sensor is placed in a zone where the influence of the magnetic dipole moment of the test specimen can be ignored. A test specimen is firmly attached on the specimen rod so that the direction of magnetization is parallel to the axis of the specimen rod, and then placed in the test apparatus as shown in Figure 2.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 the M coil; b) the SCM-Extraction method: the test specimen is extracted through the M coil. NOTE There is another method to determine the magnetic polarization of the test specimen, i.e. the SCM- Magnetometer method. In this method, variation of the magnetic polarization of the stationary test specimen due to variation of the magnetic field strength applied to the stationary test specimen is detected by the voltage induced in the detection coil (J coil) (see Annex A). The measurements are carried out at an ambient temperature of (23 ± 5) °C. For permanent magnet materials which are known to have significant temperature coefficients α(J r ) and α(H cJ ), the temperature of the test specimen should be in a range between 19 °C and 27 °C and controlled 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 temperature sensor. The demagnetization curve measured in an open magnetic circuit is influenced strongly by the self-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 field correction) should be applied to the measured demagnetization curve (see Clause 11). Magnetic properties of the permanent magnet material are determined from the corrected demagnetization curve.