Permanent Magnet Brushless Dc Motor Drive System Based On Magnetic Levitation Bearings

High speed motors have extensive application foreground,which also have sizeable value to study and analysis.The first requests are higher -speed and longer -life,and the second requests are lesser moment of inertia,lesser volume and lower losses to those high speed motors(rotate speed no less than 10000 r/min).Support system and its drive system of high speed rotator are the key factors to implement high speed performance.The conventional mechanical bearings can not meet the request,but magnetic bearings turn into the perfect choice to the support system of high speed rotator because of its great advantages,for example,higher speed,non- mechanical loss,non-lubricant,long life and high stability.The configuration and operation principle of the permanent magnetic BLDCM(brushless DC motor) are introduced in detail in this paper,and magnetic bearings are bring forward to instead of conventional mechanical bearings as the support system.In order to improve the magnetic bearings stability and easy to control,permanent t magnetic BLDCM(brushless DC motor) adopt slotless coil to reduce the unilateral magnetic force and ripple torque.But slotless coil can lead the equivalent air-gap larger,which also lead the radial air-gap magnetic flux density distribute different along the axes direction and tangent direction.Based on the larger equivalent air-gap and small length to radius of the permanent magnetic BLDCM configuration, calculate out the air-gap magnetic flux density distribute of different radius along axes direction and tangent direction by electromagnetic field numerical calculate method,the conception and calculate methods of the equivalent leakage coefficients and equivalent air-gap magnetic flux density are bring forward by the author and discussed in this paper,which provide basic theoretic foundation for electromagnetic field design of this type motor.The test result of the sample motor is almost the same with the calculation data,and the error can be acceptable according to the design request,which show the electromagnetic field calculation method applied in this paper is reasonable to this type BLDC motor design,which meet the engineering precision needs.Permanent magnetic BLDCM based on magnetic bearing supporting have larger air-gap,which can reduce air-gap magnetic flux density.Although the HALBACH configuration can be adopt to improve air-gap magnetic flux density by enlarging magnet thickness,nevertheless the air-gap magnetic flux density of this motor configuration is sine curve,which is not fit for permanent magnetic BLDCM driven by quadrate wave current.This paper bring forward one restructured HALBACH magnet configuration by attached two pieces of magnets to every pole,and also did the farther analysis and research.