Abstract
This paper investigates both static and dynamic eccentricities in single phase brushless DC (BLDC) motors and analyzes the effect of the PM magnetization field on unbalanced magnetic forces acting on the rotor. Three common types of PM magnetization field patterns including radial, parallel and sinusoidal magnetizations are considered. In both static and dynamic eccentricities, harmonic components of the unbalanced magnetic forces on the rotor are extracted and analyzed. Based on simulation results, the magnetization fields that produce the lowest and highest unbalanced magnetic forces are determined in rotor eccentricity conditions.
Highlights
Rotor eccentricity occurs when an unbalanced air gap exists between the stator and the rotor
It should be noted that in the design of permanent magnet motors for high-precision applications, it is sometimes necessary to have a detailed analysis of the effect of rotor eccentricity [6]
Static eccentricity with which the rotor is displaced from the stator center but is still turning upon its own axis O2 can be modeled by assuming ε and as constants [2], that the position of the minimal radial air gap length is fixed in space and that there is a steady pull in one direction
Summary
Rotor eccentricity occurs when an unbalanced air gap exists between the stator and the rotor. Static eccentricity with which the rotor is displaced from the stator center but is still turning upon its own axis O2 can be modeled by assuming ε and as constants [2], that the position of the minimal radial air gap length is fixed in space and that there is a steady pull in one direction This makes the unbalanced magnetic force difficult to be detected unless special equipment is used, which is impractical for motors in service. Dynamic eccentricity produces a radial magnetic pull that rotates at the mechanical speed of the motor and acts directly on the rotor This makes the unbalanced magnetic force easier to detect by vibration or current monitoring [4].
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