Orienting and assigning terminals to coil conductor regions in 3D periodical domains

Introduction

This chapter explains how to assign a coil conductor region of type without losses, with losses and simplified geometrical description or with losses and detailed geometrical description to volumes and discusses the procedure required to create its electric terminals and define the current sense when a periodicity exists in a Flux 3D project.

When the Flux 3D project contains a periodicity, the orientation procedure is influenced by the presence of a symmetry condition imposing a tangent magnetic field at the boundaries of the FEM domain (allowing the representation of only a part of the device) and thus deserves a special attention from the user.

In the following sections, the example of a three-phase rotating machine winding will be adopted to explain:

Example of a rotating machine

Such a region may be cut by the periodic planes or by a symmetry plane with physical aspects Tangent magnetic fields.

3-phase windings of a rotating machine. There are three phases: phase A (orange), phase B (purple) and phase C (green) and one region per phase
A quarter of the device is described due to a periodicity	Half a quarter of the device is described due to a periodicity and a Tangent magnetic fields symmetry

Figure 1. Names of coil conductor regions of the rotating machine

Attention: In the case of a coil conductor region with losses and detailed geometry, the user must assign one region per group of non-connected volumes, in this case the regions should be set as shown below:

PHASE_A_1	PHASE_B_1	PHASE_C_1
PHASE_A_2	PHASE_B_2	PHASE_C_2
PHASE_A_3	PHASE_B_3	PHASE_C_3
PHASE_A_4	PHASE_B_4	PHASE_C_4
PHASE_A_5	PHASE_B_5	PHASE_C_5

Figure 2. Names of coil conductor regions with losses and detailed geometrical description of the rotating machine

How to assign a coil conductor region to volumes when it is cut by the periodicity planes?

The volumes of a coil conductor region must correspond to a whole coil. When the periodicity planes cut such a region, its volumes are split into two separate groups of contiguous volumes. The two groups are linked by their periodic faces, as described in the following figures.

This section explains how to assign a coil conductor region to volumes when it is cut by the periodicity planes by one of the following commands:

• Assign regions to volumes (completion mode)
• Assign regions to volumes (modification mode)

	Part of region PHASE_A. It consists of one contiguous volume	Another volume of the region PHASE_A. It is split into two separate groups of contiguous volumes, because it is cut by periodicity planes.
With a symmetry plane
Without any symmetry plane

You must select all the volumes of a coil conductor region by the command Assign regions to volumes (completion mode) or Assign regions to volumes (modification mode).

How to define the electric terminals?

These four cases are addressed in the following subsections.

Cyclic or anticyclic periodicity:

When there is a cyclic or anticyclic periodicity, at least one internal face (i.e. faces on the boundaries of the coil volumes are not allowed) representing a cross section of the coil is required. If no such face exists, you must create some by entering the Modeler Context, or by another way. These faces do not have to be in the same plane or orthogonal to the current density. The way of defining the terminals for a coil with the command Orient wires of coil conductor region (completion/modification mode) is described below. It depends whether the region is cut by the periodicity planes or not:

• Select internal terminals,
• Select the faces of the input / output terminal intersecting the coil,
• Select the line indicating the side of the input terminal and the positive current direction.

The selected faces and lines for the terminals of regions of phases A, B and C must be so that the current is turning in the same direction in coils of phase A and B, and in the opposite direction in phase C to have a rotating magnetic flux density in the air gap of the machine, according to the theory of the rotating magnetic fields.

Selection of the faces and line of the input terminal of regions for cyclic periodicity
Cyclic periodicity PHASE_A
Cyclic periodicity PHASE_B PHASE_C

Selection of the faces and line of the input terminal of regions for anticyclic periodicity
Anticyclic periodicity PHASE_A
Anticyclic periodicity PHASE_B PHASE_C

Cyclic periodicity and “Tangent magnetic fields” symmetry:

When there is a cyclic periodicity and a Tangent magnetic fields symmetry, the faces of the terminals to select are those located on the symmetry plane. The way of defining the terminals for a coil with the command Orient wires of coil conductor region (completion/modification mode) is described below. It depends whether the region is cut by the periodicity planes or not:

• Select external terminals,
• Select the faces of the input terminal. They are located on the symmetry plane,
• Select the faces of the output terminal. They are located on the symmetry plane.

The selected faces for the terminals of coils of phases A, B and C must be so that the current is turning in the same direction in coils of phase A and B, and in the opposite direction in phase C to have a rotating magnetic flux density in the air gap of the machine, according to the theory of the rotating magnetic fields.

Selection of the faces of the terminal of regions (view from underneath)
PHASE_A
PHASE_B PHASE_C

Anticyclic periodicity and “Tangent magnetic fields” symmetry:

When there is an anticyclic periodicity and a Tangent magnetic fields symmetry, the faces of the terminals to select are those located on the symmetry plane.

The procedure of defining the terminals for a coil with the command Assign regions to volumes (completion/modification mode) is described below. It depends whether the region is cut by the periodicity planes or not:

• If the region is not cut by the periodicity planes, for a part of region PHASE_A:
  • Select external terminals,
  • Select the faces of the input terminal. They are located on the symmetry plane,
    • Select the faces of the output terminal. They are located on the symmetry plane.
• If the region is cut by the periodicity planes and the positive current enters the region on the symmetry plane, for a part of regions PHASE_A and PHASE_B:
  • Select external terminals,
  • Select the faces of the input terminal. They are located on the symmetry plane,
  • Select no face for the output terminal.
• If the region is cut by the periodicity planes and the positive current comes out of the region on the symmetry plane, for region PHASE_C:
  • Select external terminals,
  • Select no face for the input terminal,
  • Select the faces of the output terminal. They are located on the symmetry plane.

The selected faces for the terminals of coils of phases A, B and C must be so that the current is turning in the same direction in coils of phase A and B, and in the opposite direction in phase C to have a rotating magnetic flux density in the air gap of the machine, according to the theory of the rotating magnetic fields.

Selection of the faces of the terminals of regions (view from underneath)
PHASE_A
PHASE_B PHASE_C

Alternative approach to define the electric terminals in projects without a physical symmetry

Under certain circumstances, coil conductor regions reuniting the following characteresitics may exist in a Flux project:

• the coil conductor region is cut by the periodicity planes;
• the coil conductor region does not have internal faces that could be assigned to an internal terminal;
• the coil conductor region is not cut by a symmetry plane enforcing the physical condition Tangential magnetic fields, normal electric fields.

An example of such a coil conductor region is given by the ring-shaped conductor shown below (and by the coil conductor region PHASE_C in the rotating machine example considered above as well). In such cases, it is easier to create the required electric terminal on the periodicity planes, and the procedure depends on the periodicity type. These two possibilities are covered in the next two paragraphs.

Figure 3. Example of a ring-shape coil conductor region in a FEM domain with a 90^o periodicity.

Further reading

• Current orientation of coil conductor regions in Flux 3D.
• Coil entities in symmetrical or periodical domains.