Can very high voltage and very low current AC produce strong magnetic flux in the coil?

Question

I have done some research and also conducted some experiments and found that the magnetic flux in a transformer or a coil mainly depends on the number of turns and current flowing in it and not the voltage, we call it ampere-turns.

What I know is, during long distance transmission of electricity, they first step it up to very high voltages and very low current electricity and then at the receiving end, they step it down to low voltage and high current electricity.

I was wondering, at the receiving end, during step down process how do they manage to build magnetic flux with very high voltage but very low current AC?

Answer 1

Lots of thin wire. Flux in the core is generated by current flowing around it, it doesn't care how that current is organised. You can imagine it just being one thick copper ring. That has a rather low resistance, so you split it into lots and lots of small rings, cut the rings open at one point, connect them all in series instead of in parallel and, because in series they will not have equal voltage where they touch, isolate them with laquer or something else.

For your resistive power rating (in a big transformer, the magnetic core may be responsible for significant losses too), the weight of the copper ring is what mostly matters (and of course, the cooling you can run through it for large transformers). Depending on how the power is divided into voltage and current, you need to split that copper into smaller or larger wires to have the current run around the magnetic core as often as it will stand for given your available voltage.

Answer 2

Can very high voltage and very low current AC produce strong magnetic flux in the coil?

The current in each turn of a coil creates magnetic flux. Even though the current may be small, if there are many turns in the coil, a large amount of flux may be created. The step-down transformers in the power grid have many turns in their primary windings.(and fewer in their secondaries).

Answer 3

Flux is defined as the integral of voltage over time. For a sine wave, we have:

$$ \Phi = \frac{V}{2 \pi F}$$

To obtain "strong magnetic flux", simply increase the voltage and decrease the frequency.

An ideal transformer draws no current, so the current is irrelevant. (Transmission transformers can be made close enough to ideal that this remains true.)