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Old 07-19-2008, 03:49 PM
adeel adeel is offline
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Join Date: Jun 2008
Posts: 16
Smile relationship between core size and turns in transformer

hi, friends i got a problem need ur help .
i have two cores of size 1.5 * 2 and 1.5 * 2.5 i am surprised how many turns i have to use for primary in 1.5*2 core and how many in 1.5 * 2.5
iron core. detail is
for 220 volts 50/60 hz
for 275 volts 50/60 hz
and for secndary 24 volts when using 220 primary winding

i realy want to know if core size changes then how turns changes is there any easy formula to determine turns and core size . i found 400 tuns for core size 1.5*2 and 350 turns for core 1.5*2.5 is it rite for primary windings
i will be very thankfull to u if u can solve my problem . thanks
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Old 07-19-2008, 03:59 PM
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SgtWookie SgtWookie is offline
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Join Date: Jul 2007
Location: In the vast midwest of the USA; CST
Posts: 22,038

Basically, the larger the core size, the more efficient it is. No, there isn't an easy formula.
Here is a good page to get a lot of information on how transformers work, and lots of transformer theory.
General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input.
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Old 07-19-2008, 05:04 PM
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John Luciani John Luciani is offline
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Join Date: Apr 2007
Location: Massachusetts
Posts: 477

To determine inductance the formula is

N^2 = L / AL

N is the number of turns, L is the inductance, AL is the nominal core inductance that
is specified in the manufacturers datasheet. There is a lot of information about transformer
design at

Your larger core has a larger cross sectional area (and larger AL) which reduces the
number of turns required to get the same inductance.

(* jcl *)
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