Simplified projective method dedicated to rotating machines

Introduction

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 type of collection allows the computation of forces on a mesh and exporting the data to OptiStruct, to setup a NVH analysis of an electrical machine.

The following topics are covered in this page:

Description of the approach

This approach is based on two data supports, a support for data collection and a virtual support. The support to collect the data may be either imported or created from a Flux mesh with the help of the data supports, as shown in Figure 1. The virtual support is a cylinder defined by its radius and mandatorily centered at (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 cylindrical coordinates on the virtual support and then projected on the support for the data collection.

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 specific collection dedicated to rotating electrical 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 dialog box New Forces data collection, select Simplified projective method dedicated to rotating machines
In the Collection support drop-down menu, select the data support on which data will be collected.
For the definition of the virtual support, two options are available in the Definition of the computation cylinder drop-down menu. They are:
- User defined: in this case, the cylinder radius, its length unit and the number of computation points along the perimeter must be provided manually.
  Note: The number of computation points along the perimeter field is pre-filled with 1080 computation points.
  Automatically defined: in this case, Flux will automatically determine the radius of the cylinder and its discretization.
  Note: The Automatically defined option is not available in Flux 3D.
Finally, choose the interval for data collection in the Collect interval drop-down menu. The following options are available:
- Collect for all the steps of the scenario
- Collect only for the current step
- Collect for a specified interval: in this case, choose the parameter and its minimum and maximum values definining the selected interval of the scenario.
Click OK.
Right click on the forces data collection just created in the data tree and run the Collect data command.

Note: At this point, the forces may be visualized with the help of Data visualizers and/or exported to OptiStruct (as discussed in the following chapter Data export).

Limitations

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 in the rotor or in the stator parts and the virtual support must result in an air or vacuum region.

Example of application

In this example, the goal is computing the global force on each tooth of the electrical machine shown in Figure 1 after solving a scenario in Flux.

To achieve this, a support to collect the data is imported from OptiStruct, as showin in part (a) of Figure 1. On this support, forces are computed with the Simplified projective method dedicated to rotating machines as described in the previous section.

The radius automatically computed by Flux is located between the sliding cylinder (which corresponds to the line between the different mechanical set entities) 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 forces data collection is created, and the command Collect data is executed, the forces may be 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.