# Electrical sub-systems and circuit coupling

## Introduction

In order to correctly understand the difference between an internal sub-system and an external electrical sub-system, several reminders on the electrical coupling in Flux are presented in this paragraph. For more details, see chapter “Kinematic coupling: principles”.

## Circuit coupling: reminders

The conductors related to the circuit coupling are of two types:

• solid conductors: bar-shaped conductors, plate-shaped conductors, etc. These can be the site of the localization of important eddy currents.
• stranded conductors: fine wire coils

These conductors are represented twice:

• once in the electric circuit, as:
• components of the stranded conductor type
• components of the solid conductor type
• once in the finite element domain, as:
• regions of the stranded conductor type (or non meshed coils in 3D)
• regions of the solid conductor type

## Electric sub-system: definition

The “external part” of an electric circuit, i.e. the assembly of electric components other than the components coupled with the FE* domain, is called the external electric sub-system.

The number of external electric sub-systems is equal to the number of independent electric circuits.

Note: * The components coupled with the finite elements domain (components of the stranded conductor type and components of the solid conductor type) do not belong to the external electric sub-system, since the corresponding regions (regions of stranded conductor or solid conductor types) already belong to the internal sub-system (FE domain).

## Particular case

It is important to analyze the following particular case:

• There is no circuit coupling (in the usual sense of the term)
• There are stranded conductors supplied by current sources

The supplying of the stranded conductor is seen as an electrical sub-system.