（1） For the magnetic properties of various permanent magnet materials provided in relevant manuals, they are usually typical data from national standards or factory enterprise standards. However, the actual magnetic properties of permanent magnet materials are related to the specific manufacturing process of the manufacturer, and there is a deviation between the value and the standard. Moreover, the performance data specified in the standard or product samples are based on the test performance of samples with specific shape and size (for example, the standard sample of NdFeB permanent magnet material is a cylinder with diameter of 10 mm × 7 mm). For the shape and size of the permanent magnet actually used in the motor, there will be some differences between the magnetic performance and the standard value. Therefore, in order to improve the accuracy of motor design and calculation, it is necessary to ask the manufacturer for the actual demagnetization curve of the actual size of the batch of permanent magnet at room temperature and the maximum working temperature. It is better to sample and directly measure the demagnetization curve. For motors with high consistency requirements, it is more necessary to test the permanent magnet one by one.

（2） The magnetic properties of permanent magnetic materials are not only related to alloy composition and manufacturing process, but also related to magnetic field heat treatment process. For anisotropic permanent magnet, the direction of magnetic field should be the same as that of magnetic field heat treatment, otherwise the magnetic properties will be reduced.

（3） Before use, the magnetic stabilization treatment (or aging treatment) with the highest working temperature shall be carried out to eliminate the irreversible loss in advance. Ferrite permanent magnet material is different, because its coercive force temperature coefficient is positive, the lower the temperature is, the smaller the coercive force is, so it needs to carry out negative temperature magnetic stabilization treatment. It should be pointed out that the permanent magnet can not be magnetized after the high temperature or negative temperature stabilizing treatment; if it is necessary to magnetize again, the high temperature and negative temperature stabilizing treatment should be carried out again.