Dear Group. I have now got my model behaving reasonable well and get results that tie up with the actual rotor. I am trying to reduce the cogging torque and have looked at a halbach magnetisation process. My current rotor is 6 pole (radial), femm predicts that a 6 pole halbach has minimal savings, over the redial. A 4 pole halbach can produce aprox. 1/4 of the normal torque (leaving the stator as 6 pole) but a 4 pole (6 stator poles) radial magnetisation will be comparable to to hallbach cogging torque. I don't (yet?) have a halbach fixture but I do have a four pole fixture that fits the same rotor and physical tests agree with in 10-20% of femm ie only 1/4 of the original cogging torque. I am stuck with the 6 pole stator but can easily adjust the magnet. Does this tie up with other peoples results of this type of work ( I though hallbach produced very low cogging torques) (maybe I am doing it wrong!). Any other suggestions would be most welcome Best Regards Robin Cornelius robin.cornelius@xxxxxxxxxxxxxxxxxxx Hirst Magnetic Instruments Ltd Tesla House Tregoniggie Industrial Estate Falmouth Cornwall TR11 4SN UK Tel: +44 (0)1326 372734 Fax: +44 (0)1326 378069 Web: www.hirst-magnetics.com
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