Skew

The .xgdf file can define skew motors in which an angle exists between the rotation axis and the stator or the rotor (or both).

As skew is a 3D geometrical feature, you can only model it in Simcenter STAR-CCM+ using the Thermal Model geometry.
Rotor Stator




In the .xgdf file, the skew settings are specified through the following parameters:
rotor Specifies the skew settings for the rotor.
stator Specifies the skew settings for the stator.
mode Specifies the skew mode. Valid values are:
  • 0 - none
  • 1 - linear
  • 2 - stepped
  • 3 - V-linear
  • 4 - V-stepped
angle Specifies the skew angle about the Z-axis of the global origin, using the right-hand rule. The angle can be negative or positive.
  • if mode = 0: the angle = 0 and is ignored
  • if mode = 1 or 2: the angle is across the full length of the section.
  • if mode = 3 or 4: the angle is across half the length of the section.
slices Specifies the number of steps in a stepped skew model:
  • if mode = 0, 1, or 3: the number of slices = 1 and is ignored.
  • if mode = 2 or 4: the number of slices = the number of steps across the length of the section.
sections Specifies the number of repeatable units of the model, as described by the mode, angle, and slices settings.
symmetry Specifies the symmetry of the sections when the model contains two or more sections. The valid values are:
  • 0 - each section is a repeat of the previous section.
  • 1 - each section is a mirror image of the previous section.

If sections = 1, symmetry = 0.

For example: 

<skew>
  <rotor>
    <mode> 1 </mode>
    <angle> 30 </angle>
    <slices> 2 </slices>
    <sections> 1 </sections>
    <symmetry> 0 </symmetry>
  </rotor>
  <stator>
    <mode> 0 </mode>
    <angle> 0 </angle>
    <slices> 1 </slices>
    <sections> 1 </sections>
    <symmetry> 0 </symmetry>
  </stator>
</skew>
The following diagrams illustrate the settings that you can make for each skew mode. Each example shows a single section, and the skew angle α is the same for each.



1 Skew mode is Linear; skew angle is α .
2 Skew mode is Stepped; skew angle is α ; number of slices is 5.
3 Skew mode is V-Linear; skew angle is α .
4 Skew mode is V-Stepped; skew angle is α ; number of slices is 5.
NoteSector models only support the linear skew mode. For all other skew modes, create the whole motor geometry.

Whole motor with V-Linear skew mode (mode 3) Sector motor with Linear skew mode (mode 1)