How can a transformer's primary winding take in ac supply?

Question

inductors oppose ac current, then how can ac current be supplied to transformers?

Answer 1

Because the voltage leads the current by 90 degrees.So by the time the inductor opposes the current it has already gone.

Answer 2

Well that's exactly it.

In a transformer you usually want something out the other side.

It gets to the other side by going through a magnetic field in the middle.

It's really this magnetic field that happens with any inductor that gets the reputation for "opposing" as it takes current to establish the field & this is out of phase with the voltage.

For an efficient transformer, the secondary will also have an emf, electric field induced by the magnetic field.  The load on the secondary will be reflected (seen) in the primary so it won't seem to oppose quite as much as the plain inductor.

But you are right, depending on what the transformer is for (power, switch supply, RF coupling, voltage change for high-power drivers) you design the transformer inductance to get the properties you want: to get the inductance, opposition, phasing, characteristics you want.