# Ferrite core turns

#### climatex

Jul 14, 2011
37
Hi folks.

Let's say that this is the primary of a C-cored ferrite transformer. My question is, how many windings does the primary have? I was always confused in this.

If we count the full turns without the "leads", we get 6 this way. If we assume that the "starting" and "ending" leads make a one single turn, now it's 7. However if we count the beginning and the end as single turns, it is 8, as in the picture.

Now, what's the correct way? I'm confused. I think there are 7 turns on the primary, but I dunno..

Best regards.

#### duke37

Jan 9, 2011
5,364
It is the number of complete turns, count the number going through the core i.e. seven,

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
Consider a wire passing through the centre of core. How many turns is that?

Consider that the rest o f the circuit is made up of some connection between the ends of the wire and that happens outside the core, that makes up a single turn.

Consider a loop of wire that has been passed through the centre of the core (goes in and out on the same side). How many turns?

The answer is zero because you add the number of passes through in one direction, less the number passing in the opposite direction.

How is this applied to your case? Simply count all the times the wire passes through the centre of the core -- in your case it's all in one direction -- and that is the answer.

If you place your numbering on the other side (i.e. on the inner side) of the core, the answer is immediately given.

This does not apply so easily if the core is a rod or a bobbin where the flux is not completely contained. In those cases it is possible to have a fractional number of turns.

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