# About transformers: very little primary current if the secondary is unloaded

This extract is from a popular electronics book:

... a transformer of turns ratio $n$ increases the impedance by $n^2$. There is very little primary current if the secondary is unloaded.

I'm thinking about the emboldened part. Please see if the following argument is correct: If the secondary is unloaded, its current is zero, so the secondary can be neglected (as if it doesn't exist at all), and the transformer can be modeled as a single inductor with inductance of $L$. And according to the relations

$$X_L=2\pi\nu L$$

and

$$V=X_L I,$$

$L$ must be large if primary current is 'very little'.

• Look up transformer equivalent model. The secondary current will dominate the primary so much you can offer omit the magnitizing current. At very light load however, it’s a significant portion of the primary current. Sep 11, 2018 at 15:41
• Related question and answer Sep 11, 2018 at 17:16