Abstract
In this paper the effects of using a partially magnetized bonded neo (NdFeB) magnet in an automotive accessory motor are presented. The potential reason for partial saturation of the bonded neo magnet is explained and a simple method to ensure saturation of the magnet is discussed. A magnetizing fixture design using the 2-D Finite element analysis (FEA) is presented. The motor performance at various magnet saturation levels has been estimated using the 2-D FEA. Details of the thermal demagnetization test adopted by the automotive industry is also discussed and results of the motor performance for four saturation levels are detailed. These results indicate that the effect of demagnetization is more adverse in a motor with partially saturated magnets.
Highlights
Bonded neo magnet based motors are fast gaining popularity in automotive accessory applications as they offer substantial weight/size reduction and efficiency improvement over the traditional ferrite based motors
Bonded neo magnets are isotropic in nature compared to the anisotropic nature of ferrite magnets and need special attention for the magnetizing fixture design to achieve the desired magnetization profile and full saturation
Ferrite magnets have been the traditional choice for the automotive accessory motors, leading to the possibility that during the magnetization of bonded neo magnet one uses the magnetizing energy needed to saturate the ferrite magnet by mistake
Summary
Bonded neo magnet based motors are fast gaining popularity in automotive accessory applications as they offer substantial weight/size reduction and efficiency improvement over the traditional ferrite based motors. Ferrite magnets have been the traditional choice for the automotive accessory motors, leading to the possibility that during the magnetization of bonded neo magnet one uses the magnetizing energy needed to saturate the ferrite magnet by mistake. In such a case, application of insufficient magnetizing field and/or inappropriate magnetizing fixture will lead to a partially saturated bonded neo magnet. Motor performance for different saturation level of bonded neo magnets before and after the demagnetization test is presented and the effect of partial saturation is quantified.
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