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德语Permanent Magnet Assembly was founded in 1959 to increase understanding, promotion, and effective use of permanent magnetic materials. Originally operating as the Magnetic Materials Producers Association (MMPA), PMD became part of A3 Motion Control & Motors in 2003 as its International Magnet Manufacturers Association counterpart; since 2015 PMD has also become part of A3 Motion Control & Motors representing global manufacturers who produce electric motors, drives, and the associated components needed by such solutions.
Electrical machines containing internal permanent magnets require careful handling, assembly and fixation to achieve maximum effectiveness. This is due to a wide range of topologies with various magnet sizes and shapes as well as humidity and aggressive substances present, shocks or vibrations potentially having negative impacts on them such as changes in air gap dimensions which affect reluctance of circuit and lead to irreversible losses; such changes usually happen around operating points that lie below knee of coercivity curve causing irreparable losses which must be resolved efficiently or they become permanent sources of losses which need be resolved promptly in order to avoid negative impacts on them from both sources.
To reduce the effects of these reluctance changes on MR performance, it is advised that magnets be pre-exposed to expected reluctance changes by pre-exposing them. This can be accomplished by subjecting magnets to higher-than-expected fields prior to being mounted into machines; this step ensures that operating points won't fall below knee of coercivity slope, leading to irreparable losses within magnets.
An important consideration in creating a safe magnet assembly is its surface condition and internal geometry. Surface condition is determined by both the material used to manufacture magnets as well as any coatings applied after production; for instance uncoated Samarium Cobalt and Alnico materials must be handled carefully during magnetization as they can fracture easily; additionally they should be stored so as to avoid contact between like poles, which could cause irreversible but remagnetizable losses.
Internal geometry is determined by the shapes and arrangement of magnets bonded together. A common solution involves epoxy paint, powder coating or tape bonding techniques to attach individual magnets in modular fashion to their supporting base plates. Not only do these solutions offer structural support and easy magnet installation into rotor yokes, they provide additional protection from vibration, impact and chemical/humidity influences. Magnets may also be protected with mechanical protection in the form of straps glued onto them and the first base plate. Dependent upon their application, straps may also serve as additional structural elements and mechanical seals for magnet-base plate assemblies. This method of attachment is especially attractive in applications where large amounts of adhesive material may be a problem, and reduces adhesive needs by more than 80%.
Magnetic Rotor Assemblies
