- The maximum temperature of the magnet is not a fixed value. It depends on the material's magnetic grade. The temperature is normally from 80℃ to 230℃. The temperature limits depends on the material's Curie temperature and highest working temperature. The Curie temperature is the critical point which will lose the magnetic performance of the magnet. The highest working temperature is the long term working temperature which could garantee the magnet performace steady. It could avoid to make the irreversible magnetization.
- The core pinciple to choose high temperature resistance grade is that the real working temperature must be lower than the magnetic grade's highest working temperature. You also need to reserve 20-30℃ the safety space. Normally the high temperature resistance grade is N(80℃),M(100℃),H(120℃),SH(150℃),UH(180℃)or higher. The temperature we show is the highest working temperature. When you select the magnetic grade, you not only need to consider the environment temperature, you also need to add the temperature rise during the magnet in the alternating field or eddy current effect. For example, in the electric vehicle motor or magnetic driving system, the working environment temperature is high probaby. You need to choose the H grade or higher grade of the magnet.
- All the magnetic performance of the magnet will be reduced in high temperature environment. The magnetic force attenuation of the magnet in the rated working temperature is reversible. When it cooled, the magnetic force will be recover. However, if your temperature goes above the critical point, it will happen the irreversible lose. The magnetic force will be reduced with the temperature increasing. The key is to distinguish the magnetic force is revisible or irrevisible. In high working temperature, the magnetic reduction is revisible. We need to concern the date of the temperature coefficient of Br and coercive force temperature coefficient.
