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For a 12-0-12 Step Down Center Tapped Transformer, what should be the direction of the winding on secondary coils (One End - CT, CT - Other End)? Should they be in opposite direction? If it is 'same direction' would it have any relation with primary windings direction? Note: the transformer will be used in reverse to step up voltage in a DC-AC Square Wave inverter where the CT will always receive +ve DC voltage.

Also, is there any change required in terms of winding direction, if used in a Full Bridge inverter?

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    \$\begingroup\$ A reverse Step Down is called Step Up, so please simplify your description. The transformer does not care about transforming the voltage up or down ;-) What does the 12-0-12 mean? \$\endgroup\$
    – auoa
    Commented Feb 1, 2017 at 22:26
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    \$\begingroup\$ A 12-0-12 winding is just continuous. If you imagine winding a single 24 V secondary, but right in the middle of it were to scrape bare a very short segment and solder a "centertap" to that bare spot, you'd roughly have it. What I do is bring out about an inch or two of wire at the half-way point, kink and fold it back to the core, and continue winding in exactly the same direction as before. Later, I clean the kinked end and use it as the centertap. \$\endgroup\$
    – jonk
    Commented Feb 1, 2017 at 23:01
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    \$\begingroup\$ The orientation of secondary winding for isolated AC does not matter, but impedance ratio does matter. 1:10 voltage ratio raises source impedance 1:100, so source must be very low to start with. What I do is fold a magnet wire in two then wind the pair if you want matched outputs to avoid DC imbalance, then reverse one pair connections to create the center tap. \$\endgroup\$
    – D.A.S.
    Commented Feb 1, 2017 at 23:06
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    \$\begingroup\$ The term "CT" is normally reserved for "current transformer" and definitely not "centre tapped". Please amend to avoid confusion and attract more answers (none at present). \$\endgroup\$
    – Andy aka
    Commented Feb 2, 2017 at 8:29
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    \$\begingroup\$ I meant wind in pairs gives best matching, but you'll get 0 inductance this way, so folded end must be cut and one pc. connected to other wire end becomes C Tap. This is called "Bifilar Method" \$\endgroup\$
    – D.A.S.
    Commented Feb 2, 2017 at 16:34

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If it is 'same direction' would it have any relation with primary windings direction?

The two windings are wound in the same direction just like this little ferrite wound component: -

enter image description here

If the centre-tap wasn't there the orange and red would be one continuous winding in the same direction.

The direction that both have in reference to the primary winding is of no-importance for AC power transformers but, in other applications like transformer fed loudspeaker arrays it would make a massive difference at bass frequencies if one transformer had the opposite phase to another.

Also, is there any change required in terms of winding direction, if used in a Full Bridge inverter?

No.

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  • \$\begingroup\$ That makes it clear to me. Yhanks for the response with an easy to understand image. \$\endgroup\$
    – sribasu
    Commented Feb 3, 2017 at 6:53

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