Electrical machines usually consist of copper windings on steel cores, and their AC resistance is greater than their DC resistance.
The power loss has two components which are nonlinear with frequency and flux density:
Eddy Current Loss
The un-wired 230V terminals of the 230V:30V transformer may have 230V on them (or more if more is applied to the transformer. Caution is advised.
Limit the output from the Variac to 30V, otherwise the low-impedance load of the 230V"30V transformer will draw too much current, blowing the fuse in the Variac.
Configure the circuit so that the Variac feeds the isolating transformer, which in turn feeds the 30V winding of the 230V:30V transformer. Add in the meters like so:
Ensure the two scope earth leads are connected together:
Channel 1 is the voltage supplied to the magnetic load
Channel 2 is the current drawn by the magnetic load
Consider the voltage, current, power factor and waveforms at differing applied voltages (eg 5V, 10V ... 30V)
You should note all your measurements, thoughts, and observations.
In writing your conclusions, and should you decide to use this lab for you finial write-up lab, consider:
What you observed
What the theory says you should have observed.
What discrepancies you encountered
What have you learned, and can you conclude from this
What problems are posed by using this in industry, and how these are addressed.