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Thermal stability, test methods and results analysis of permanent magnetic materials
1, the thermal stability of permanent magnetic materials
Temperature stability refers to the extent to which the permanent magnet changes magnetic properties caused by changes in the ambient temperature. Magnetic stability is the degree of change in magnetic properties caused by the application of an external magnetic field [3]. When the permanent magnet motor is in operation, due to the influence of the temperature rise of the motor and the existence of the armature winding, the performance of the permanent magnetic material in the permanent magnet motor is influenced by both the temperature and the magnetic field. Therefore, the temperature stability and magnetic stability are collectively referred to as thermal stability in the analysis of this paper. That is, when the permanent magnetic material is heated to a different temperature and a reversely applied magnetic field is applied, the permanent magnet exhibits a change in the magnetic properties, that is, the temperature coefficient of the residual magnetic density of the permanent magnetic material at different temperatures and the intrinsic coercive force. The temperature coefficient and the change of the inflection point on the demagnetization curve.
2, test methods and results analysis
The measuring instrument is a special rare earth permanent magnet detection device. The testing principle is to calculate the B-H curve through the measured J-H curve. First, the sample is magnetized, then the testing equipment is initialized, the sample is finally installed, and the sample is heated to a predetermined temperature, and the test program is started to test, and the measured curve is recorded and printed by the computer.
The test work mainly starts from the following aspects:
(1) Test a piece of permanent magnet at different positions for cutting standard samples;
(2) Test different permanent magnets (mainly φ10×10 standard samples) of the same manufacturer and the same brand;
(3) Test the bulk sample of the same SH brand.
2.1 Test points for thermal stability at different locations of the same sample
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