GB/T 40794-2021 Measurement method of irreversible magnetic flux loss due to high temperature of rare earth permanent magnet
1 Scope
This document specifies the measurement method of irreversible magnetic flux loss due to high temperature of rare earth permanent magnet.
This document is applicable to the measurement of irreversible magnetic flux loss due to high temperature of neodymium iron boron permanent magnet.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 6379.2 Accuracy (trueness and precision) of measurement methods and results - Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
GB/T 9637 Electrotechnical terminology - Magnetic materials and components
GB/T 38437 Methods of measurement of the magnetic dipole moment of a ferromagnetic material specimen by the withdrawal or rotation method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 9637 and the following apply.
3.1
irreversible magnetic flux loss due to high temperature
loss that occurs when a magnet is taken from room temperature to high temperature for some period but cannot be recovered when the magnet is returned to room temperature
Note: It is expressed as a percentage (%).
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3.2
load line
trajectory of the operating point of the permanent magnet forming part of a given magnetic circuit as the magnetization magnitude of a permanent magnet changes
Note: The operating point of a permanent magnet is defined as a point on the demagnetization curve or recovery line of the permanent magnet that forms part of a given magnetic circuit. Its coordinates are the magnetic flux density and magnetic field strength in an operating state.
[Source: GB/T 9637-2001, 221-04-11]
3.3
high temperature aging
test in which the thermal stability of a permanent magnet is tested under a high-temperature environment stimulated after the permanent magnet is insulated at a certain temperature in a high-temperature test chamber for a period of time
4 Method and principle
Helmholtz coils and fluxmeters are used under the same room temperature to test the irreversible loss, expressed as a percentage (%), of magnetic flux (magnetic dipole moment) of magnetically saturated magnets before and after the high temperature aging.
5 Test conditions
5.1 The ambient temperature magnetic flux test shall be conducted at an ambient temperature of 23°C±3°C.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Method and principle
5 Test conditions
6 Apparatus
7 Samples
8 Test procedures
9 Test data processing
10 Uncertainty
11 Test report
Annex A (Informative) Change pattern and causes of irreversible magnetic flux loss due to high temperature of rare earth permanent magnet versus temperature
