Coil conductor regions with losses and detailed geometrical description
Overview
Coil conductor regions with losses and detailed geometrical description are now available in Transient Magnetic applications in Flux 2D. This feature was already available for Steady State AC Magnetic applications in previous versions of both Flux 2D and Flux 3D.
During its creation, this surface region asks the user for a detailed description of the winding geometrical features. This additional information allows Flux to consider the proximity and the skin effects through a special homogenization technique, and thus improves the estimation of Joule losses in the winding during post-processing.
- Rectangular section wire;
- Circular section wire defined by the diameter of the wire;
- Circular section wire defined by the fill factor of the coil.
Using the new coil conductor region with losses and detailed geometrical description spares the user from representing each turn of the coil with an individual solid conductor region (linked to its corresponding FE coupling component in a complicated electric circuit). While this latter approach is also legitimate and rigorous, it is usually very time consuming to set up in Flux due to the elaborate geometry and the refined mesh required. Moreover, the solving time with the new coil conductor region is significantly reduced when compared to a solid conductor approach.
The "Convert current application" feature is fully compatible with this new coil conductor region type in Flux 2D. Consequently, it may be used to switch from a Steady State AC Magnetic project already containing this type of region to a Transient Magnetic Application and vice-versa.
Example of application
To compare the use of solid conductor regions and coil conductor regions with losses and detailed geometrical description in a Flux 2D Transient Magnetic application, let us consider a project modeling a three-phase, eight-pole permanent magnet synchronous machine (PMSM). The three-phase winding is distributed between several stator slots, with one phase per slot. Moreover, each phase has 25 turns per slot and is formed from a stranded copper conductor composed of 7 wires in parallel, with circular cross-section. The three-phase winding is fed by current sources in the external circuit.
図 1 displays a first modeling approach for this device based upon the use of several solid conductor regions. Each phase coil strand must be explicitly represented in the geometry, and each circular surface associated with a wire is assigned to an individual solid conductor region. Moreover, each solid conductor region is linked to its own FE coupling component (2-terminal solid conductor type).
図 1. A Flux 2D project modeling a three-phase PMSM with solid conductor regions. Each coil strand is assigned to a Solid Conductor region shown in (a). The coupled electric circuit containing one FE coupling component per solid Conductor region is shown in (b). A detailed view of a machine slot is depicted in (c).
図 2, on the other hand, displays the same machine modeled with a different approach. The coil strands are no longer represented individually in the geometry and a single coil conductor region with losses and detailed geometrical description is assigned to a rectangular surface enclosing the winding in each slot. Consequently, only one FE coupling component (Stranded coil conductor type) is required per phase, and both the geometry description and the representation of the external circuit become easier to set-up.
図 2. The same machine, but now modeled in Flux 2D with coil conductor regions with losses and detailed geometrical description. Remark that the geometrical description of the winding (a) and the representation of the external circuit (b) become straightforward when compared to the previous approach based on solid conductor regions.
The losses evaluated in the coil conductor region follow the same speed behavior predicted by the first modeling approach using several solid conductor regions, as shown in 図 3 below. Each speed value in the graph corresponds to a transient simulation with 100 time steps in the computation scenario.
図 3. Comparison between the behavior of the Joule losses depending on the speed of the PMSM evaluated with different modeling approaches in Flux.
| Approach | Number of mesh nodes | Computation time |
|---|---|---|
| Solid conductor | 102626 | 1 hour |
| Coil conductor region with losses and detailed geometrical description | 5552 | 5 minutes |