# What is occurring when the less coils on the secondary create more current?

Discussion in 'General Electronics Chat' started by foolios, Dec 6, 2009.

1. ### foolios Thread Starter Active Member

Feb 4, 2009
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1
The reading explains that the higher voltage and more turns on the primary then step down because of the lesser turns in the secondary which then results in less voltage. This change causes the lesser current on the primary side to change into higher current in the secondary side.

Ok, I see that in the secondary side, the wiring is bigger so this leads me to think that this allows more electrons to be affected. Maybe that's why the current rises. But then it would depend on whether this is always the case, if the secondary side had to be a bigger conducter. But if that's not always necessary, then that blows this theory up.
If the wire size can be the same, how does more current get pushed through the conducter when the voltage is lower?

2. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Note that a transformer has the property that power in equals power out. That is why a step down transformer produces more current at the stepped-down voltage. The power transfer is not lossless but most transformers are fairly efficient. At least when operated in their designed frequency range.

hgmjr

3. ### foolios Thread Starter Active Member

Feb 4, 2009
160
1
Does this mean that the conductors on the secondary side HAVE to be larger?

4. ### hgmjr Moderator

Jan 28, 2005
9,030
214
That would typically be the case.

hgmjr

5. ### davebee Well-Known Member

Oct 22, 2008
539
46
The primary current generates magnetic flux. In the secondary, enough current flows to just balance that flux.

If the secondary has fewer turns, then more current must flow in each turn of the secondary to generate the same flux as was generated by the primary.

The size of the conductor has absolutely nothing to do with this property of the transformer.

Each conductor will be sized for the amount of current it is expected to carry, so the side that is expected to carry a higher current will typically be larger. But the conductor size is just a practical matter to keep the transformer from overheating.

6. ### foolios Thread Starter Active Member

Feb 4, 2009
160
1
If you have something that demonstrates this, I would love to see it.

If the secondary has fewer turns, then more current must flow in each turn of the secondary to generate the same flux as was generated by the primary.

Thanks for the explanations. I'm not sure I can grasp it at the moment, but I will keep coming back to this as I'm learning to try and see if it sinks in a little more.

7. ### davebee Well-Known Member

Oct 22, 2008
539
46
I should say that my first explanation is not really technically accurate. It's really more that the changing magnetic flux from the changing primary current generates a voltage in each secondary turn. If the secondary is connected in a complete circuit then secondary current will flow. The flux generated by that current opposes the flux generated by the primary, so more secondary current flow allows more primary current to flow, and power is sent across the transformer.

You can see that there's a lot going on in a transformer; it gets complicated pretty fast, which is why I offered a simple explanation first.

What do you mean something that demonstrates it? A transformer demonstrates it.

8. ### foolios Thread Starter Active Member

Feb 4, 2009
160
1
If there was some graphical representation of what you write.

Oct 22, 2008
539
46