Question How can I specify that a conductor is made of aluminum with a steel core (in HIFREQ)?
The conductor model in HIFREQ allows you to define a (possibly) hollow metallic part surrounded by an optional coating. It doesn't presently allow for the modelling of two different metallic components.
A good approach to model a conductor consisting of a steel core surrounded by aluminum is to model only the aluminum, i.e. use a hollow conductor with an internal radius equal to that of the steel core and an outer radius equal to that of the conductor as a whole. The reason is that most of the current will be flowing in the aluminum since it is a much better conductor than the steel and also as a result of the skin effect, which tends to confine the current near the surface of the conductor. We have used such a model several times, with good success.
To define the characteristics of the conductor:
Go to Input Toolbox for HIFREQ and click on System.
In the System screen, click on Characteristics.
In the Characteristics screen, the Conductor Types data table allows you to define different types of conductors. You can define several properties of the conductors. In the case of interest, you should define the following properties in row 1:
The "Relative Resistivity" (with respect to annealed copper) should be about 1.6 (the resistivity of aluminum)
The "Internal Radius" should be set to the desired value.
The remaining fields can be left to their default values. Note that the outer radius of the conductor is specified in the System screen.
To assign this conductor type to the desired conductor(s), return to the System screen by clicking OK. Set the "Conductor Type" of the desired conductor(s) to 1, and define their radius.