Simplified projective method dedicated to rotating machines


This chapter discusses the use of the Simplified projective method dedicated to rotating machines to create force collections in the Import / Export data context : this kind of collection allows to compute forces on a mesh in order to export them towards OptiStruct to setup a NVH analysis of an electrical machine.

The following topics are covered in this page:

  • Description of the approach
  • Creation of this force collection
  • Limitations
  • Example

Description of the approach

This approach is based on two data supports, a support for the data collect and a virtual support. The support to collect the data can be either imported or created from the Flux mesh with the help of the data supports as it is shown in Figure 1. The virtual support is a cylinder defined by a radius and mandatorily centered in (0,0) in the XY plane as shown in the Figure 1. Radial and tangential magnetic pressures are computed with the Maxwell tensor approach in cylinder coordinates and can be integrated with several methods on the virtual cylindrical support; finally, they are projected on the support for the data collect.
Note: The virtual support (cylinder) is not visible in Flux.

Figure 1. Permanent magnet synchronous machine with two data supports: (a) the OptiStruct-imported support to collect the data and (b) the virtual cylinder.

Creation of this collection

This type of collection dedicated to electrical rotating machines is available in all Flux modules (2D, 3D and Skew) for static and transient magnetic applications. Its creation is made via the following steps:
  • In the data tree, select the menu Forces data collection
  • In the dedicated GUI for Forces data collection, select Simplified projective method dedicated to rotating machines
  • In the Definition tab:
    1. Fill a value for the radius of the virtual support or let it in the automatic mode
    2. Choose a data support to collect the data
  • In the Advanced tab, (those fields are already filled with default values)
    1. Fill the Minimum number of computation points along the perimeter which must be an integer. Its default value is 1080 points.
    2. Fill the Maximum projection distance (0 for optimal value). Its default value is 0 (optimal value).
  • Choose the collection interval:
    • Collect for all the steps of the scenario
    • Collect only for the current step
    • Collect for a specified interval
  • Click OK
  • Right click on the forces data collection just created in the data tree and run the command Collect data
Note: In advanced mode, more integration options are available, see this page.
Note: As a next step, forces can be visualized with the Data visualizers and / or exported towards OptiStruct with the Data export.


  • The support to collect the data must be cylindrical and centered on (0,0) in the XY plane, even for 3D and Skew applications.
  • The axial forces (i.e. along the cylinder axis) are equal to 0.
  • The virtual support and the support to collect the data must be in the same mechanical set.
  • The radius chosen for the virtual data support must not be stuck to the rotor or to the stator part and must be in an air or vacuum region.


In this example, the aim is to compute the global force on each tooth of the electrical machine described in Figure 1 after solving a scenario in Flux.

To this aim, a support to collect the data is imported from OptiStruct which is the same as part (a) of Figure 1; on this support, forces are computed with the Simplified projective method dedicated to rotating machines described before.

The radius automatically computed by Flux is located between the sliding cylinder (which corresponds to the line between the different mechanical sets) and the stator region as shown in the figure below:

Figure 2. Definition of the radius for the virtual support: in red the sliding cylinder, in black the virtual cylinder to compute the magnetic pressures.
Once the radius is correctly defined, the data must be collected with a right click and the command Collect data on the forces data collection; forces can now be visualized with the Data visualizers as shown in the figure below:

Figure 3. Visualization of global forces per tooth for a permanent magnet synchronous machine: (a) the forces normal to the collect support, (b) the forces tangential to the collect support.