PD IEC TR 62518 pdf download Rare earth sintered magnets — Stability of the magnetic properties at elevated temperatures
The scope of this technical report is to describe the temperature behaviour of rare earth sintered magnets in detail for use in designing magnetic circuits exposed to elevated temperatures. The temperature behaviour of SmCo 5 , Sm 2 Co 1 7 and Nd-Fe-B sintered magnets is described.
The various changes of open circuit flux which can occur due to temperature are discussed in Clause 4. The long term stability of the magnets is discussed in Clause 5. The experimental procedures are described in Clause 6. Results of the measurements of the flux loss occurring at the ambient temperature after heating isothermally at 50 °C, 75 °C, 1 00 °C, 1 25 °C, 1 50 °C and 200 °C for up to 1 000 h are given in Clause 7. The effect of length to diameter ratio (L/D) of the magnet samples and the influence of H cJ on the flux loss were also studied. The results are discussed in Clause 8.
The data in this technical report was provided by the Institute of Electrical Engineers of Japan (IEEJ) and its subcommittees. This data has been gathered from the members of these sub- committees.
The temperature stability correlated with the complex corrosion behaviour and the spin reorientation phenomena at cryogenic temperatures will not be given in this technical report.
2 Normative references
IEC 60050-1 21 , International Electrotechnical Vocabulary − Part 121: Electromagnetism
IEC 60050-1 51 , International Electrotechnical Vocabulary − Part 151: Electrical and magnetic devices
IEC 60050-221 :1 990, International Electrotechnical Vocabulary − Chapter 221: Magnetic materials and components
Amendment 1 (1 993)
IEC 60404-8-1 , Magnetic materials − Part 8-1: Specifications for individual materials − Magnetically hard materials
3 Terms and definitions
For the purpose of this document, the following terms and definitions apply. In addition, most of the technical terms used in this document are defined in IEC 60050-1 21 , IEC 60050-1 51 , and IEC 60404-8-1 (the product standard).
loss the reduction due to an external influence, primarily temperature, in the flux of permanent magnets in a magnetized state, unit of Wb. Three kinds of flux loss, reversible flux loss, irreversible flux loss and permanent flux loss, are used to discuss the temperature stability of rare earth sintered magnets.
reversible flux loss
a magnetization change which is recovered by the removal of a disturbing influence such as temperature. Irreversible flux loss is the partial demagnetization change caused by the temperature changes. The irreversible flux loss is fully recovered by remagnetization. Permanent flux loss is caused by permanent change in the metallurgical state and is generally time and temperature dependent. The permanent loss cannot be recovered to the initial magnetization value by remagnetization.