# Transient Magnetic: presentation and typical examples

## Presentation

The Transient Magnetic application allows the study of the phenomena created by a time variable magnetic field. The magnetic field is related to the presence of variable currents (and possibly permanent magnets).

This application allows the consideration of induced currents in conducting regions (Eddy currents). It allows the consideration of skin effects and proximity effects in the conducting regions, too.

## Utilization

The Transient Magnetic application can be used for different types of devices. We are principally interested in the study of devices supplied by current of varied shape (echelon, trapezoid…) or by transient phenomena (linked to current variation caused by powering, short circuits…)

The Transient Magnetic application is principally used with Circuit coupling* and/or Kinematics coupling* for rotating machines, transformers, etc. study in transient state.

* See following chapters:

## Typical example

Two typical examples, that correspond to two types of problem can be distinguished:

• magnetic problems
• conduction problems

These two typical problems are presented in the following blocs.

## Principal results

The principal results that can be obtained with the Transient Magnetic application are:

• the same as for Magneto Static application
• induced currents, dissipated power by Joule effect in the solid conductors

These quantities can be obtained under the form of a time dependant evolutive curve.

By means of these quantities, it is possible to compute inductances…

## Typical example (1)

A first typical example of a problem treated as a Transient Magnetic application is presented in the figure below. This is an example without coupling with an external circuit .

 air or vacuum magnetic media (non conducting) conducting media (non magnetic) without EC * conducting media (magnetic or not) with possible EC* Note: *EC = Eddy current

## Passive conductor: definition

In the previous example (1) the conducting media is known as passive (): the current is induced. This is also called a conductor only fed "by induction".

## Typical example (2)

A second typical example of a problem treated as a Transient Magnetic application is presented in the figure below. This is an example with coupling with an external circuit.

 air or vacuum magnetic media (non conducting) conducting media (non magnetic) without EC * conducting media (magnetic or not) with possible EC* Note: *EC = Eddy current

## Active conductor: definition

In the previous example (2) the conducting media could be:

• a passive () media: as in the previous case
• an active () media: the conductor is supplied by an external current or voltage source.