 | 115 - Eccentricity Analysis of an SPM Motor UP!
| Module:DP | 2013-04-26 | Motors have many parts, which must be assembled correctly for a usable product. Even if each part is made within acceptable limits for manufacturing errors, when various parts with small errors are put together, the errors can have a cumulative effect. In particular, if eccentricity (deviation, deflection) occurs in the cylindrical axis of the rotor and stator, the magnetic flux density distribution and electromagnetic force can become unbalanced, causing vibration and noise. Ideally, parts would be manufactured without any errors, but in reality, error reduction requires precise mechanical manufacturing, which means a huge increase in costs. This is why it is necessary to figure out the tolerance zone of trade-off between settings and performance for each part at the design stage.
In order to grasp these at the design stage, highly precise evaluation sensitive to parts' manufacturing errors is needed, so electromagnetic field analysis using the finite element method (FEM) is effective.
This Application Note presents how to evaluate the cogging torque waveform and effects on the electromagnetic force acting on the stator in an SPM motor with and without eccentricity.
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  | 93 - Cogging Torque Analysis of a Motor with 8 Poles and 9 Slots Accounting for Eccentricity
| Module:DP | 2010-08-31 | Eccentricity can occur on the center axis or the rotation axis of a motor. It is advantageous to evaluate the effects of eccentricity because it can cause vibrations and noise and break the symmetry of the magnetic flux density distribution and the electromagnetic force.
This example presents the use of a magnetic field analysis to obtain the cogging torque and electromagnetic force with and without eccentricity.
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 | 23 - Eccentricity Analysis of an IPM Motor
| Module:DP | 2013-01-28 | One of the causes behind motor vibration and noise is the eccentricity of the rotor. It is well known that the torque in a motor is generated when the electromagnetic attraction and repulsion are produced by the stator and rotor, but the attraction force between the rotor and stator is not well recognized. This is because generally the rotor and stator are positioned at the center which makes it look as if the attraction is balanced out. Therefore an error occurs in the calculation for the parts that support the shaft or stator and the concentric circle is not supported in which the attraction is not canceled. The radial load is constantly moving which generates friction loss in the bearing when an electromagnetic force is unbalanced causing vibration and sound. Also, the tolerance needs to be calculated to a certain extent in the mechanical process. The tradeoff between the amount of eccentricity and the electromagnetic force needs to be specified in the design.
The error in calculation is not large to the point where parts cannot be constructed, but a very small difference of 1/10mm occurs in the eccentricity amount when constructing. To evaluate the small difference in the geometry, a magnetic field analysis using a finite element method with a level of detail in shape deformation that can respond to the accuracy needs to be calculated.
This note presents how electromagnetic force changes when modifying the eccentricity amount for a rotor.
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